The EGR valve only opens under certain conditions while driving. On the OEM style EGR valves, you can actually open the valve by hand by sticking a finger up through a hole on the underside of the valve housing and pushing the valve open. The engine will stumble. If your EGR valve does not have the holes in the underside of the EGR housing, a vacuum pump will open the valve... and again, the engine should stumble. I personally don't feel your elevated idle RPM speed is EGR related.
Another way to test the EGR valve is to remove the vacuum hose and open the valve by hand by sticking a finger up through a hole on the underside of the valve housing and pushing the valve open. While open, put a finger over the port where the vacuum hose goes and release the valve. If the valve diaphragm is OK, you should feel suction at the port and the valve should remain open, Removing you finger, the valve should close.
Paul, the instructions for the cable in your link says it won’t work on 85 V6’s and that’s what I have. Strangely, the other one that’s $114.95 does say it will work with 85 V’s. I’m confused. 🙁 Also, I really would like to bite the bullet and get the scan tool, especially because it seems these idling & driveability issues are non-stop. 🙁 Patrick, as I mentioned previously I’m going to do the iac port block off ((while running) test today. Vintage- Nut (and others) thanks for the info on the egr valve. I will test that later with the Mighty Mite and see if I can verify operation. Kit
The Coolant Temperature Sensor (CTS) goes to the ECM. Based on this ECM circuity and the coefficient direction of this sensor, the voltage to the Analog to Digital Converter (ADC) inside the ECM rises as temperature goes up. So it has a positive temperature coefficient overall. My GUI displays this as raw hexadecimal, raw decimal, and in degrees F or degrees C.
The Manifold Air Temperature (MAT) Sensor called the Intake Air Temperature (IAT) Sensor on the Fiero goes to the ECM. This nomeclature difference is because GM decided to measure air temperature at the Air Cleaner rather than in the Intake Plenum (Manifold). Based on this ECM circuity and the coefficient direction of this sensor, the voltage to the ADC inside the ECM falls as temperature goes up. So it has a negative temperature coefficient overall. My GUI displays this as raw hexadecimal, raw decimal, and in degrees F or degrees C.
The Manifold Absolute Pressure (MAP) Sensor goes to the ECM. Based on this ECM circuity and the coefficient direction of this sensor, the voltage to the ADC inside the ECM rises as pressure goes up (or so called vacuum decreases). So it has a positive pressure coefficient overall. My GUI displays this as raw hexadecimal, raw decimal, and in inches of Mercury (inHg) or millimeters of Mercury (mmHg).
When I was coding my GUI, I found tables (similar to the CTS table shown previously). I also measured their resistances at 0 C, 25 C, and 100 C, and various pressures respectively. Then I correlated those to what the ECM reported in raw decimal. Then I performed polynomial curve fits (from all those data points) to find the polynomial coefficients so I calculate the temperature in C (or pressure in mmHg) directly from the raw decimal value. I still have the curves for the CTS, the IAT Sensor, and the MAP Sensor. Since the GUI does all the conversions for the user, I never showed these curves. But since they may help users in diagnostics and testing these sensors, I am going to add these curve graphs to the GUI so you can see each sensor in: temperature/pressure vs. resistance vs. voltage vs. ADC raw value vs. units in F or C/inHg or mmHg.
Sorry, but that is true. The 1985 V6 ECM uses a slightly different ALDL stream. And all the IL4 ECMs had even more different ALDL streams.
It took me years (off and on) and empirical observations and experiments to figure out what all the 1986 to 1988 V6 data streams meant.
If I had an 1985 V6 ECM, I could upgrade the GUI to "decode" it as well.
But there is no one source with ALL the information needed to fully decode each ALDL data stream - GM was never forthcoming with that. I found hints and clues as I came across them (sometimes conflicting info) which took years.
If GM would give me (not gonna happen) the ALDL data stream specs on how to decode each data word, then the GUI could do them all - but the 4 cylinder ECMs used the 8192 baud rate and that may be too fast for the GUI to handle with all the things it's does in real time.
If anyone has a 1985 V6 ECM I can borrow, I should be able to reverse the data streams and code the GUI to process them.
[This message has been edited by Romsk (edited 04-22-2025).]
The $84.95 Fiero GT ALDL Adapter shown my web page and one of those sold by The Fiero Store, is the one I designed. I offer support and free consultations on using it.
The $114 Scan Tool also sold by The Fiero Store is not mine. Therefore, I don't support it or consult on using it.
Maybe try Red Devil River for the 1985 V6 ECM.
[This message has been edited by Romsk (edited 04-22-2025).]
No, I didn’t forget about swapping a spare map sensor. 😊 Paul, thanks for all that info. I sent 2-3 emails to that Red Devil guy a long time ago but he never responded. I finally gave up trying to contact him. Ok, here is what I did this afternoon: 1) Installed new AC/Delco pcv valve 2) Swapped MAP sensors (I have 3 spares- all are used- one of the 3 is a factory GM Map so I installed it. 3) Started car with throttle body boot off. (engine dead cold) 4) Engine went right to 2450 rpm and stayed there. Let it run for about 4 minutes. 5) Put finger inside throttle body and plugged IAC hole/port. Engine rpm went way down immediately (almost to stalling) but came back up to about 500-600 rpm and would continue to run even though my finger was still plugging the hole. 6) I did this finger plugging test about 3 times and I can tell you the engine didn’t like it! I took my finger off the hole, gave it some gas by twisting the throttle valve and it would run rough, sputter and then it died twice. Then I noticed the SES light was on. 🙁 7) Started car back up and it went back up to virtually 2900 rpm and stayed there even when fully warm. 8) During the later part of this testing I also tested the egr valve. I applied about 15 hg of vacuum to the egr port itself and the rpm’s did go down but it also started to sputter & bog down too. At this point the engine was running so high in rpm I just shut it off.
I am about ready to quit on this car. It’s getting extremely frustrating. 🙁 Before I started these tests this afternoon, it would at least idle down to 1400 when warm but now its racing at 2900 rpm when fully warm. At this point the car is virtually undriveable. 🙁 Kit
[This message has been edited by Kitskaboodle (edited 04-23-2025).]
No, I didn’t forget about swapping a spare map sensor. 😊 Paul, thanks for all that info. I sent 2-3 emails to that Red Devil guy a long time ago but he never responded. I finally gave up trying to contact him. Ok, here is what I did this afternoon: 1) Installed new AC/Delco pcv valve 2) Swapped MAP sensors (I have 3 spares- all are used- one of the 3 is a factory GM Map so I installed it. 3) Started car with throttle body boot off. (engine dead cold) 4) Engine went right to 2450 rpm and stayed there. Let it run for about 4 minutes. 5) Put finger inside throttle body and plugged IAC hole/port. Engine rpm went way down immediately (almost to stalling) but came back up to about 500-600 rpm and would continue to run even though my finger was still plugging the hole. 6) I did this finger plugging test about 3 times and I can tell you the engine didn’t like it! I took my finger off the hole, gave it some gas by twisting the throttle valve and it would run rough, sputter and then it died twice. Then I noticed the SES light was on. 🙁 7) Started car back up and it went back up to virtually 2900 rpm and stayed there even when fully warm. 8) During the later part of this testing I also tested the egr valve. I applied about 15 hg of vacuum to the egr port itself and the rpm’s did go down but it also started to sputter & bog down too. At this point the engine was running so high in rpm I just shut it off.
I am about ready to quit on this car. It’s getting extremely frustrating. 🙁 Before I started these tests this afternoon, it would at least idle down to 1400 when warm but now its racing at 2900 rpm when fully warm. At this point the car is virtually undriveable. 🙁 Kit
sounds like patrick was onto something, the engine should completely stall when you plug the iac so its sucking air past the throttle blades also it really wants that air boot on so it can pull air past the sensor in the cannister could you show me how you installed the iac and your throttle blade please? ill grab a picture of mine off the gt so you can see what its supposed to look like (ignore the extra spring that you might see. a previous owner installed it and i havent got around to dropping the cradle to fix that and a bunch of leaky gaskets and corroded parts, why do the throttle bodies corrode so darn bad? the really bad one is the old one that ran fine)
[This message has been edited by cartercarbaficionado (edited 04-23-2025).]
Put finger inside throttle body and plugged IAC hole/port. Engine rpm went way down immediately (almost to stalling) but came back up to about 500-600 rpm and would continue to run even though my finger was still plugging the hole.
The engine should've stalled, and you've already confirmed that there is no vacuum leak downstream of the TB. Whether the idle set screw on the TB still has the factory plug covering it or not, IMO the idle set screw needs to be adjusted. If it was me, I'd remove the plug, and then with the engine running, I'd slowly back off the set screw until the engine stalls while your finger is covering the IAC port.
It's possible the TPS would need to be adjusted afterwards, as it's supposed to be .5v with the throttle shaft positioned at idle. (Don't bend the tang. Rotate the TPS unit instead).
There could still be a problem with the IAC valve not performing as it should (due to the valve itself or ECU/sensors/wiring), but one step at a time.
[This message has been edited by Patrick (edited 04-24-2025).]
Yes, if the 1985 data stream is similar it should not take me long. I made a test sled with Pogo Pins for my 1987 SE that I had laying around. I can use it for the 1985 ECM. If it has different connectors, I will just make a new sled for it. I will look for a schematic so I can stimulate the signals and see what the ALDL data does. That should make short work of it.
My email is: romsk22@gmail.com. +1(603)465-7225
I am in Hollis, NH.
My wife and I go to Wells beach all the time. We could meet for lunch somewhere near Brunswick, lunch is on me. Email me when you can and we can hash out the details.
If this pans out, maybe I can borrow 4 cylinder ECMs from other enthusiasts. It would be nice for my GUI and Adapter to work with every stock Fiero.
Thanks, Paul ------------ Kit,
I corresponded with the Red Devil River guy just over a year ago. Suddenly he stopped replying.
There are other options. There are simple adapters you can make if you have an old Laptop PC with a real Comms Port. If not, you will need an Adapter that converts the data to USB. Then you can use WinALDL as your GUI. Like my GUI, WinALDL is free. It is used by a lot of people (not just Fiero folks).
I can modify my Adapter design for use with WinALDL, but it will take me a few weeks. I could sell it to you for parts cost (no profit) plus shipping. Somewhere around $55.
It's not a fast solution, but it may be worth your while in the long run.
Email me and we can colaborate.
I will need a good photo of your ALDL Connector to verify if it is using pin M for 8192 Baud, or pin E for 160 Baud.
On the TPS, bending the Tab is not recommended. Loosening the mounting screws and rotating the sensor is best. Sometimes you have to widen the holes on the sensor with a file to get it read 0.5V on the middle pin to GND in the idle position. After adjusting, it is best to reset the ECM.
Some Fieros have a connector on the Fusable Link near the battery. This removes power only to the ECM (the only way to reset it). If you don't have it or can't find it, simply remove the Negative cable on your battery for at least 1 minute (I like 5 to be sure). This will reset the ECM. Removing the Fuse in the Fuse panel will not reset the ECM memory.
For those of you not familar with the IAC Valve: It's impossible to test with an old school Automotive Test Probe. It uses 4 fast digital signals because it is a stepper motor, not just a Solenoid. Two wires control one set of coils in the stepper motor, the other two wires control the other set of coils. The ECM sends pulses and reverses their polarity in various sequences to step the Pintle of the IAC Valve in and out in tiny increments. The sequence is rather difficult to see unless you have an Oscilloscope.
I designed a IAC Valve signal tester but never built it. I never got a mating cable, but Alligator clips may work. If anyone is interested I can make one for you (cost only plus shipping of course).
It is simple. It uses LEDs that you can watch to see if all 4 wires are activated and if the polarities are changing. It's not as good as bench testing (I can tell you how) but it is a quick indicator.
Another way is to remove the IAC Valve and have someone put the car in and out of DMDIAG Mode so you can watch the Pintle go in and out. Be careful, some of the IAC Vales don't have a stop and the Pintle and spring may pop out... so watch for that. This happens when some other user "pulled" the Pinle out and broke the internal stop. Only "Push" the Pintle in before installing. If the IAC Valve Pintle has a broken stop, it can still be used, but you have watch it if it pops out during testing.
That gives me an idea. I make an ALDL "Paperclip" Adapter. I could modify it with a remote switch and cable so you can switch between NORM and DMDIAG Modes and watch the IAC Valve without an assistant. If anyone is interested let me know.
[This message has been edited by Romsk (edited 04-24-2025).]
Check the condition of the two rubber hoses and curved metal pipe that runs from the underside of the throttle body to the intake manifold.
quote
Originally posted by olejoedad:
If there are no external vacuum leaks, it is possible that your lower intake manifold gasket could be leaking, pulling air from the "oil gallery".
I know we're all trying to help Kit out here, but with all due respect Joe, you may be forgetting that Kit's engine stalls (as it should) when the entire mouth of the TB is covered. Correct me if I'm wrong (please do!), but does this not rule out air being drawn into the intake system from the "underside of the throttle body" or from the "oil gallery".
quote
Originally posted by Vintage-Nut:
As your TB has the factory idle screw plug, I believe you really need to find the root cause than attempting to adjust the screw.
Why are you so convinced that the root cause (or at least an additional issue) can't be a throttle plate that isn't closing far enough? Is it simply because there happens to be a plug in place? Do you know for a fact that the plug itself may not have been replaced after someone earlier may've misadjusted the throttle stop set screw? If enough air is getting through to run the engine with the IAC air passage completely blocked, and air is not entering the system anywhere else (as determined by the engine stalling with the TB mouth completely blocked), then where else but air getting past the throttle plate is air getting in? Educate us!
[This message has been edited by Patrick (edited 04-24-2025).]
Patrick, as I mentioned I looked over the throttle plate very carefully and it seems to be fully closing. I agree on the argument that since fully blocking the tb mouth made it die abruptly, that kind of rules out a vacuum leak at the upper plenum. Anyways, because it was asked, I took an inspection mirror and a flashlight and checked the two rubber lines that attach to the underside of the throttle body (they both have rubber elbows) and the metal tube that plugs into the lower part of the throttle body and everything seems to be good and tight. What was also asked is about my iac installation. I believe I did everything correct on it. (I measured the pintle on the new one and confirmed it was very close to 1 and 1/16 so I didn’t feel I needed to adjust it. And yes, I followed the correct procedure for resetting it and took it for a 1/2 hour freeway drive. I know I seated it all the way in correctly. See pic below.
Ok, at this point I wanted to throw out a question: some are saying to mess with the idle screw. You know, I’ve had this high idle issue for maybe 4 months or so and before this the idle was ok. The point is the car has idled fine for most of the time I’ve had it (since 2006) I’m hesitant to adjust the idle when it was never needed in the past. I’m thinking the next step (before proceeding with anything else) is to get the scan tool because right now I feel like I’m “grasping at straws” and these latest tests have made the engine go from bad to worse. (yes, I know you guys are trying to help and I’m very grateful for that) 😌 Kit
[This message has been edited by Kitskaboodle (edited 04-24-2025).]
Patrick, as I mentioned I looked over the throttle plate very carefully and it seems to be fully closing. I agree on the argument that since fully blocking the tb mouth made it die abruptly, that kind of rules out a vacuum leak at the upper plenum. Anyways, because it was asked, I took an inspection mirror and a flashlight and checked the two rubber lines that attach to the underside of the throttle body (they both have rubber elbows) and the metal tube that plugs into the lower part of the throttle body and everything seems to be good and tight. What was also asked is about my iac installation. I believe I did everything correct on it. (I measured the pintle on the new one and confirmed it was very close to 1 and 1/16 so I didn’t feel I needed to adjust it. And yes, I followed the correct procedure for resetting it and took it for a 1/2 hour freeway drive. I know I seated it all the way in correctly. See pic below.
Ok, at this point I wanted to throw out a question: some are saying to mess with the idle screw. You know, I’ve had this high idle issue for maybe 4 months or so and before this the idle was ok. The point is the car has idled fine for most of the time I’ve had it (since 2006) I’m hesitant to adjust the idle when it was never needed in the past. I’m thinking the next step (before proceeding with anything else) is to get the scan tool because right now I feel like I’m “grasping at straws” and these latest tests have made the engine go from bad to worse. (yes, I know you guys are trying to help and I’m very grateful for that) 😌 Kit
did you do anything to it 4 months ago? also i dont see a gasket on the iac unless its grey and the iac can be weird with gasket thicknesses, plus you have tried a few map sensors and ive had horrible luck with those and they suck to test
Why are you so convinced that the root cause (or at least an additional issue) can't be a throttle plate that isn't closing far enough? Is it simply because there happens to be a plug in place? Do you know for a fact that the plug itself may not have been replaced after someone earlier may've misadjusted the throttle stop set screw? If enough air is getting through to run the engine with the IAC air passage completely blocked, and air is not entering the system anywhere else (as determined by the engine stalling with the TB mouth completely blocked), then where else but air getting past the throttle plate is air getting in? Educate us!
I agree on the argument that since fully blocking the tb mouth made it die abruptly, that kind of rules out a vacuum leak at the upper plenum.
IMO, it rules out any kind of an air leak from the mouth of the TB all the way to the cylinders.
quote
Originally posted by Kitskaboodle:
You know, I’ve had this high idle issue for maybe 4 months or so and before this the idle was ok. The point is the car has idled fine for most of the time I’ve had it (since 2006) I’m hesitant to adjust the idle when it was never needed in the past.
Well okay, that's a bit of information that I don't know whether we had before. I do understand your apprehension to adjust the idle stop screw, although it's not as if it's some sort of destructive action (except for sacrificing the plug over the set screw).
If the IAC valve was working properly, it should be able to stop the air flow through the port just as well as your finger does. So although I still think too much air is getting by the throttle plate... sure, you can leave it for now. I suspect there's something affecting the ability of the IAC valve from doing its job. As I said in my very first response to you, you need the ability to scan this engine to see what the heck is going on. Right now, we're all just guessing.
If either the CTS or the IAT are reporting low (actual or incorrect) temperatures to the ECU, a high idle speed will result. Either test the resistance of these sensors as mentioned above... or use WinALDL (or a scanner) to see in real time what the temperature readings are. When I've tested mine, I've done it first thing in the morning after the engine has sat all night. With the ignition key turned to RUN and the engine not running, the temperature readings from both sensors should be within a few degrees of each other, and basically the same as the ambient air temperature around the car.
[This message has been edited by Patrick (edited 04-24-2025).]
Yes, the IAC gasket is there. Oh, in case you think I forgot, I did Gumout quite thoroughly the IAC hole in the side of the throttle body after I took out the old one. And as I said, I have 3 spare MAP sensors. I tried the GM one first but if it helps I can try the other 2, although they are off brand. My throttle body butterfly looks like it’s in great shape with no corrosion like you mentioned. That and it is very clean with almost no carbon buildup. Patrick, I’m still on the fence about messing with the idle screw…. Looking into a scan tool now……. Kit
[This message has been edited by Kitskaboodle (edited 04-24-2025).]
Too bad we aren't all just hanging over your engine with beers in hand, I bet it would be resolved by now [smile]. I see a lot of good advice tossed around here. You may be looking at multiple problems, but hang in there.
On a side note: I will be borrowing a 1985 V6 ECM to revamp my GUI. I know that is no help now, but I will try my best for the future.
Me? Personally, I am not convinced that suddenly plugging the TB inlet and the engine instantly stalling is a definite diagnosis that rules out vacuum leaks. There may still be a slight leak somewhere. I feel that choking off an engine that severely and suddenly will make any engine stall instantly (even with a small vacuum leak) - there simply is not enough time for the ECM to recover from such a sudden rise in manifold absolute pressure (loss of inflow of air). But, I could be wrong... I think I was wrong once.... once [laugh].
Forgive me if already asked, did the idle problem just appear one day, or did it creep up over time?
For any of you that use my GUI, I added a Toggle ALDL Mode feature (it will be released tomorrow). You select that feature and it continuously toggles between NORM and DMDIAG Mode every couple of seconds. With Key On Egine Off (KOEO), this will allow you to test the IAC Valve by removing it and watch it go out (closed) in DMDIAG Mode and back in (open) in NORM Mode. I have a feeling that is why GM made the IAC Valve go to the closed position in DMDIAG Mode - to check the IAC Valve because there is no direct feedback of its position to the ECM.
My brother is a Subrau and BMW mechanic. He thinks that DMDIAG Mode in KOEO may also actuate the EGR Solenoid. If that is the case, we should hear the solenoid click on and off in ALDL toggle mode. --------- Kit,
I agree with Patrick, the CTS and IAT Sensor should read about the same abmbient air temperature after letting the engine cool overnight. If you can unplug each and measure the over night rest pre-start resistance of each, I can plug those into my code and tell you their temperature readings and if they are working (at least at ambient). This might be something you can do as you look for a scan tool.
...the CTS and IAT Sensor should read about the same ambient air temperature after letting the engine cool overnight. If you can unplug each and measure the over night rest pre-start resistance of each, I can plug those into my code and tell you their temperature readings and if they are working (at least at ambient).
Of course, the problem with doing this is that it doesn't help determine whether or not that sensor info is actually making it to the ECU. There could be a wiring harness issue. But yeah, it's better than not doing any sort of reading at all.
quote
Originally posted by Romsk:
Me? Personally, I am not convinced that suddenly plugging the TB inlet and the engine instantly stalling is a definite diagnosis that rules out vacuum leaks. There may still be a slight leak somewhere. I feel that choking off an engine that severely and suddenly will make any engine stall instantly (even with a small vacuum leak) - there simply is not enough time for the ECM to recover from such a sudden rise in manifold absolute pressure (loss of inflow of air).
Well, how about if Kit goes about it very slowly then? Seriously though, if the mouth of the TB was covered over bit by bit, until it was completely blocked, and the engine stalls... would that not then convince you that there are no vacuum leaks (at least not enough of a leak to account for the high idle revs)?
If Kit was a little closer to Vancouver, I'd definitely be hanging over his engine bay by now.
[This message has been edited by Patrick (edited 04-24-2025).]
I trust your judgment, but slowly covering the TB might provide some more data points.
I am an old school gear head... spraying carburetor cleaner was the only definitive way for a shadetree mechanic to determine if there are any vacuum leaks. That is too dangerous so I don't recommend it. Now they have fog (smoke) generators that are safer.
With Key On Egine Off (KOEO), this will allow you to test the IAC Valve by removing it and watch it go out (closed) in DMDIAG Mode and back in (open) in NORM Mode.
Is that really a good idea? On one of my Fieros, I powered up the IAC valve while it was removed from the TB, and the pintle shot off into the lawn!
Mine had a stop. It did not shoot off when I made a dual H bridge module and Arduino UNO bench test for it. Then I pulled the pintle out a couple of times as I was honing the code. I pulled it a little too hard, broke the internal stop, and it popped out.
So, I guess some have stops, and some don't, or someone in the past at least mishandled and broke a stop.
In my GUI help, I have details on these facts and to do it on a cool engine and to put the IAC Valve in a box in case the stop is broken or not even present. I may make a little fixture for it so the pintle can't pop out when removed from the TB.
So that GUI version is now posted on my web page for my whopping 20 users world wide [laugh].
Now I am modifying the ALDL Adapter with a tiny slide switch to select pin M 8192 Baud or pin E 160 Baud. I ran of I/O on the tiny $9 Trinket Microcontroller Board, so I have to switch the signal manually. The GUI sends mode commands to the Adapter, I have to add a command to detect 8192 Baud or 160 Baud timing. Then update the GUI code to handle the 5 different ECMs (and ALDL streams) that stock Fieros use.
My Adapter does not work like those simple adapters that try to treat the ALDL as an RS-232 data frame. Mine actually measures the pulses down to the micro second and determines if the ALDL data represents a logic 1 or 0 bit. Then the Adapter sends an ASCII '1' or '0' respectively over USB at a 500K Baud rate to the GUI. So, it will be able to convert 8192 Baud bit streams just as effectively - plenty of time between ALDL pulses.
Thanks Fierosound for the FSM screenshot. Good news is I just got my FieroStore Scantool in the mail today. Next step is to contact my friend who is giving me a free laptop. (mine is too old and missing the power brick besides) After we load the software we will get it up and running and report back with the real time parameters.
Patrick, I was thinking that same that I wish you were all physically here to assist me. Doing it by myself is kind of depressing and i feel all alone working on it by myself. Anyone have a tissue?😩 Kit
[This message has been edited by Kitskaboodle (edited 04-30-2025).]
Good news is I just got my FieroStore Scantool in the mail today. Next step is to contact my friend who is giving me a free laptop. (mine is too old and missing the power brick besides) After we load the software we will get it up and running and report back with the real time parameters.
I'm not familiar with that scan tool, I don't know what software is packaged with it and/or how the info is displayed.
With WinALDL, I found that Cliff Pennock's utility program, ALDLView, was a great help in seeing/understanding the data.
quote
Originally posted by Kitskaboodle:
I wish you were all physically here to assist me. Doing it by myself is kind of depressing and i feel all alone working on it by myself. Anyone have a tissue?😩
I usually work on my cars alone, with maybe just the cat for company. If only she had opposing thumbs, she could at least pass me the tools.
Hi gang. 😊 Wow, it’s taken a while to get to this point. I finally got my laptop / FieroStore scan tool set up. Here is the first screenshot of the data. As a reminder and as you know, I had tried some tests per your suggestions (like abruptly choking the throttle body so the engine would die) so I had a check engine light before I hooked up the scantool this afternoon. So, the trouble codes at the bottom left of the screen may not be an accurate indicator of the real problem, ok? So, before you look at the numbers in the screenshot below, I wanted to say that this first screenshot is 1 of 3 that I took with my phone that my pc was displaying. First pic represents what the program saw during the very first minute of the engine running since ice cold only. I will send pics 2 and 3 in separate replies so I don’t screw up the order. Ok, go ahead and read the parameters and let me know your thoughts. After I send you all 3 pics you’re going to see something quite wrong with the MAP voltage! It’s zero from start to finish. My understanding is that it should always read between 3.5 to 5.5 volts at all times. I heard you test MAP connector A & B with key on / engine off. But, the map has 3 prongs. Which ones are A and B? Pic would be great. 😊 Kit
If you have a GM MAP, 'ABC' are on the top of the sensor... If you have an aftermarket MAP, 'A' is frontwards {rear window} / 'C' is backwards {taillights}
PS - 'B' is in the middle....
[This message has been edited by Vintage-Nut (edited 05-08-2025).]
Ok, thanks for the connector pin info. If “B” is the middle one, that should be a no-brainer then to test it. 😌 Ok, here is pic #2. It represents the engine running after about 2 to 2.5 minutes from cold. As an fyi, the engine by this point has already settled down to about 1500 rpm and stayed this way through the end of the test. (although with the scantool connected throughout the test this may not matter due to close and open looping during the test)
Kit P.S. I forgot to point out (I noticed it) that the rpm indicated in the program says 1000 but my actual tach rpm clearly said about 1400-1500. It sure didn’t feel like it was idling at 1000. Hopefully this will not matter one way or the other.
[This message has been edited by Kitskaboodle (edited 05-08-2025).]
P.S. I forgot to point out (I noticed it) that the rpm indicated in the program says 1000 but my actual tach rpm clearly said about 1400-1500. It sure didn’t feel like it was idling at 1000. Hopefully this will not matter one way or the other.
I'd say it matters a great deal if you've been chasing a supposed high idle... and it's mostly because your tachometer is way off!
[This message has been edited by Patrick (edited 05-08-2025).]
Ok, pic #3. This represents the engine after it has been running for about 3.5 to 4 minutes or slightly more. As I said, by this point the engine pretty much stayed at about 1500 rpm. (as I mentioned above, my tach says 1500 rpm while the scantool program says it’s 1000) Ok, last point: Just out of curiosity, I shut the engine off, disconnected the scantool, waited about a minute and a half, then re-started the car to see what it would do. Well, strangely enough it went right to about 1500 rpm and stayed there but this time there was nothing connected to the aldl port. Oh, and I can confirm the engine wasn’t crazy about this test as I could swear the engine was missing here and there. (It’s rare for this engine to exhibit missing) Kit P.S. Tomorrow I am going to test the A&B prong voltage for the MAP and report back. (key on / engine off - should be between 3.5 to 5.5 volts unless I’m mistaken?)
[This message has been edited by Kitskaboodle (edited 05-08-2025).]
Patrick, ok I get your point about my tach being off. But 500 rpm off? 🙁 Oh my, that’s not acceptable. I supposed I just got used to it being off. Anyways, is there any way to adjust/re-calibrate it? I’ve never done this or heard of anyone adjusting / re-calibrating a Fiero V6 tach. Tach filter deaths I am definitely aware of and both my Fiero’s have Rodney’s filters. Ok, i got an idea. I have a newer style timing light that has a built in digital rpm gauge. I think I will hook it up “to get a third party” opinion” on the actual engine rpm. I will report this tomorrow along with the MAP connector voltage readings. Kit
[This message has been edited by Kitskaboodle (edited 05-08-2025).]
Patrick, ok I get your point about my tach being off. But 500 rpm off? 🙁 Oh my, that’s not acceptable. I supposed I just got used to it being off. Anyways, is there any way to adjust/re-calibrate it? I’ve never done this or heard of anyone adjusting / re-calibrating a Fiero V6 tach. Tach filter deaths I am definitely aware of and both my Fiero’s have Rodney’s filters. Ok, i got an idea. I have a newer style timing light that has a built in digital rpm gauge. I think I will hook it up “to get a third party” opinion” on the actual engine rpm. I will report this tomorrow along with the MAP connector voltage readings. Kit
hey kit? have you checked that your pickup in the dist and that the icm is reporting
Seriously though, if the mouth of the TB was covered over bit by bit, until it was completely blocked, and the engine stalls... would that not then convince you that there are no vacuum leaks (at least not enough of a leak to account for the high idle revs)?
Not according to the scan tool.
