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| Can I manually manipulate my idle speed? (Page 6/10) |
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olejoedad
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APR 24, 07:09 AM
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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.
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Romsk
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APR 24, 08:23 AM
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1985 Fiero GT,
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
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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.
Paul
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Romsk
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APR 24, 08:51 AM
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Patrick,
I agree.
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).]
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Vintage-Nut
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APR 24, 09:28 AM
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Hey Kit,
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.
However, you have a lot of help on this situation, so I will withdraw gracefully...
Good Luck!
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olejoedad
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APR 24, 01:42 PM
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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.
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Patrick
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APR 24, 03:17 PM
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| quote | Originally posted by olejoedad:
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.
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| 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".
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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.
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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).]
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Kitskaboodle
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APR 24, 05:47 PM
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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).]
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cartercarbaficionado
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APR 24, 06:18 PM
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| quote | Originally posted by Kitskaboodle:
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
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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
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olejoedad
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APR 24, 06:47 PM
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| quote | Originally posted by Patrick:
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!
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Good point Patrick!
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Patrick
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APR 24, 06:54 PM
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| quote | Originally posted by Kitskaboodle:
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.
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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.
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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.
| quote | Originally posted by Patrick Here:
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.
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[This message has been edited by Patrick (edited 04-24-2025).]
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