No ground connection there. Anyone know where it was supposed to come from? I'm assuming from the C500, inside the harness going to the passenger side rear lights?
Ground, G400, shown is only for rear lights, maybe Cruise servo when so optioned but only for 84-87
88 rear light goes thru C500 to ground inside of cabin.
And That is 2 points.... G201 & G202 G202 is "easy," near and below ECM. G201 is harder behind radio for most. Can barely see if look behind radio when you are under the left side of dash. Not sure on 88.
Both are unlikely damaged but frame paint and dirt can make them "weak." G201 might clean w/o pulling the radio but will need good magnet driver so don't loose the screw. Many drivers have weak magnets that may not hold here.
A lot of things are grounded there... Including Fuel Pump.
OK, finally got my diagnostic kit & cable. Thought I had figured out TunerPro RT with the $48 definition file, but I don't trust myself and obviously, some of the readings don't make sense. I measured voltage with a DVM directly at the terminals and had 13.6 V! Perhaps some of you can tell me what I am doing wrong. Here is a screen-shot of the ALDL dash and the ALDL flags.
I also have the CSV file.
BTW-Idle is still hunting, matter of fact, getting worse..........thought I was on the right rack. HELP!
ECM is telling you it reads 9.6v and likely why you have hunting idle.
You read V w/ DVM on what terminals? at battery? doesn't mean much there. Power, grounds to ECM still have problems as I posted above or ECM itself is "bad."
ECM has 2 power feeds. One directly from the battery, other from ECM fuse. Either/both can have problems. To start, Check every wire to the "box" under C500.
I would carefully unplug/plug both connectors on The ECM a few times too. Even tap w/ fingers on ECM and see if numbers change if true then likely ECM is dying.
MAT and Engine Coolant that low unless local weather in cold there but I don't think is -22°C right now. MAT can get colder then weather because is downstream of TBI w/ petrol getting on it but engine mush be cold. Engine hot MAT easily sees 150°F at idle even in cold weather. MAT also gets wide swings of temp as you drive too.
Or does someone have an 88 SM for sale? 87 SM here in Germany was sold before I had a chance to buy it.
On the ECM connectors I found the following: Had a steady 12 V on W(hite)10 & 15 (battery and ECM fuse), although scan tool told me only 9.6 V??? Had a good ground on W(hite) 12 & 13 (system ground). Had no ground on B(lack)12 (sensor ground for TPS & CTS) and on W(hite)14 (sensor ground for MAP & MAT), so I added ground by splicing in two wires to the harness and to the chassis, just for troubleshooting purposes. Peculiar though, I had ground, when measured directly at those aforementioned 4 sensors, so I assumed, I had broken wires somewhere in the harness??? Made no difference in the hunting idle, but feels like the car is running worse now. Is ground on those two connections only provided when ECM is running (ignition "ON")?
Guess I need not mention that this is driving me insane now!
Thanks for ANY suggestions, especially if I did something wrong!
Figured out that there will only be ground on BLACK12 & WHITE14 if the ECM is plugged in and gets ground on WHITE 12 & 13. (Brain Fart!) All grounds and voltages on the ECM check out.
I think I've asked this before; does a bad MAP "always" throw a code?? If I disconnect the MAP cables (not the vacuum), the car idles fine and stable. Unfortunately, it lights up the Check Wallet light and sets a code 33 or 34. I plug it back in, the hunting idle returns, but no codes.
OK, please help me out here. I've got a new scanner, which works for ALL models of Fiero (yes, also for the 87-88 DIS Duke ). Below are the scans from the warm engine, no trouble codes, what am I missing?
Scanner reading data will set ECM to Idle to 1000rpm and is normal. NORMAL Idle w/o scanning is ~ 900 RPM w/ auto trans. ECM says Bat V is fine. That's good. 5 spots for Cruise is normal when car doesn't have the option. You will never set Lean Crs turn on. GM disable the function for most cars likely to meet US EPA rules.
Many values shown are not very useful because they change every "data packet" from ECM. Put that into "Real Time" monitoring mode and you see that happen and even then data is too slow to read and have value to you. Again, See my Cave, Scan Tool Helpand More on Tools But Watch Bat V when monitoring to see if number change. Should Not change much or any. Note: Some fields names and other info for scanner you have are different and never seen 42 items on 3rd page. Iffy ECM to DIS wires can cause 42 but no clue why scanner would report this other then sees code 42.
Unplug MAP likely F's the whole engine and ECM tries to use Limp Home programing so Unplugging likely won't "Show" a bad MAP. For "fun" years ago... I've tried unplugging w/ DIS engine and can't drive w/o it. MAP is use for several things Like: Sets initial air pressure for weather/altitude Use to set ignition timing for engine load.
I need to go someplace now. post again if I think anything else later.
Coolant temperature of 80°C/176°F seems low to me for a fully warmed up engine. (Why does it also indicate 75°C?) Do you not have a 195°F thermostat installed?
[This message has been edited by Patrick (edited 05-10-2019).]
Originally posted by Patrick: Coolant temperature of 80°C/176°F seems low to me for a fully warmed up engine. Do you not have a 195°F thermostat installed?
Runtime is ECM data since engine starts = 162 Seconds and if that's all then engine is just barely warm at best. MAT is 58°C at idle too so engine is still cold. Normal "hot" engine coolant temp is around 200°F/93°C to 220°F/105°C For this engine... Intake Air at idle can see 150F/66C or more by the time MAT reads it. But hit the gas and MAT drops fast often around ambient that day. Note that DIS Dukes will go close loop as soon as ECM gets a good feed from O2 sensor and that often happens (O2 Ready) in 30 - 90 second after started.
Most times Tstant has Temp stamped somewhere on it. OE is 195F but many install 180-185 and not very good. Other even use lower or no Tstant and causes many problems and might include hunting idle. many are on the "bulb" that makes it open but some are elsewhere. If need a new one try to get Stant "Superstant." See my Cave, Thermostat
Check for Exhaust leaks... If the manifold is cracked can get enough air sucked in to mess up O2 feed for the sensor. Most time this won't cause hunting idle but won't help you either. 88 should be better because exhaust pipes made different but check anyway.
[This message has been edited by theogre (edited 05-10-2019).]
Coolant temperature of 80°C/176°F seems low to me for a fully warmed up engine. (Why does it also indicate 75°C?) Do you not have a 195°F thermostat installed?
One value is at engine start-up, other value is "real-time". While I don't know what all menu items mean, some are self explanatory (like MAP or IAC), the others are as follows: TPS Throttle Position Sensor MAP Manifold Absolute Pressure IAc Idle Air Control BPW Base Pulse Width CLT Coolant Temp MAT Manifold Air Temperature O2X O2 Crosscounts O2 O2 Sensor iNT Integrator BLM Block Learn Memory ADV Spark Advance TCC Torque Converter Clutch PN Park Neutral Switch CLC Something emissions related, I have to look that up DFCO deceleration fuel cutoff
Originally posted by Donster: This from a member of the GA Fiero Club regarding the thermostat:
"It has become a common practice to drill a 1/8 hole in the flange if it doesn't already have a little weep valve pin in it."
Is this necessary on the 88 Duke?
No. Get "superstat" in my cave. Stant and other "Normal" stats work but this is better and helps prevents fake problems that makes people think the engine has problem. Is basically have a smoother operating curve to stop dash gauge hot/cold seesaw in winter. Engine is happier too. Get Stant Caps too at same time. Stant fits better then most others. I would buy two each so have a new spare of rad and Tstat caps.
Are the radiator cap and thermostat cap identical?
Have you not looked at them? They're completely different.
quote
Originally posted by Donster:
CLT Coolant Temp MAT Manifold Air Temperature
One tip when using a scanner. After the car has sat all night, connect the scanner and without starting the engine, turn the key to the ON position and read the temperature for both the CLT and the MAT. They should both be very close to the same reading, basically the outside ambient air temperature. If not, one or both of the sensors is malfunctioning.
[This message has been edited by Patrick (edited 05-14-2019).]
One tip when using a scanner. After the car has sat all night, connect the scanner and without starting the engine, turn the key to the ON position and read the temperature for both the CLT and the MAT. They should both be very close to the same reading, basically the outside ambient air temperature. If not, one or both of the sensors is malfunctioning.
I scanned again today, paying attention to what Steve posted regarding to O2 sensor. While it does move around, I'm sure it is not in the correct range. It was one of the first things I replaced when this issue first reared it's ugly head. Just to make sure, I installed the old one again, and it had "0", ZERO readings, then the new one (which I assumed is working) would go from 0.1V to 0.9V to 1.1V to 0.4V and never zero in on a particular value. Can't be right, can it? So I disconnected the O2 sensor, and surprise, surprise! Engine runs fine, no stumble, no hunting, no idle dropping, no stalling. Downside is, it will occasionally throw a code 13 (O2 open) and the scanner tells me the engine is running lean. Before, with either O2 sensors installed, it would bounce between lean & rich by the second.
Can we now safely say that it is either the O2 sensor or the (one, purple) wire, going to the ECM that is causing my issue???
BTW: The new O2 sensor was a BOSCH, which you would expect NOT to be bad out of the box.
As I have not received the new O2 sensor yet, we have been running the car with the sensor disconnected and I must say the engine is running great without. Doesn't overheat, runs stable, no hunting idle, good mileage, good acceleration. So, what bad could happen not having the O2 sensor connected?
The ECM is using a default value for the sensor that happens to be right....(for now). The CAT may not last as long, or emissions may be higher than normal.
OK, just for closure on this topic, I wanted to report the following:
I have been running the car without (disconnected) Lambda/02 sensor now for several weeks. Can't report anything out of the ordinary, as fuel consumption, acceleration, temp, idle a.s.o. are good. It does bother me, as this is not how it should be, but I had wasted so much time with this issue, therefor I am satisfied that the car is running good without the O2 sensor.
I may address it at a later date, but for now I'd like to say thank you to all who helped me narrow it down to the O2 sensor, especially Ogre, as he promped me to redo all my ground connections, which ultimately improved so many things, albeit not entirely related to the original issue, but one can never have enough good ground connections!
UPDATE: replaced O2 sensor and ignition coils. While replacing the coils, I noticed the PIM/ICM shield was missing. Obviously the PO replaced the PIM at some point, but failed to transfer the shield from the old module over to the new module. In the beginning (long time ago) I got a code 42, but as it went away after I reset the ECM and did not return, I never gave it anymore thought.
When warm/hot I have noticed a stutter during low RPMs, and of course, my hunting idle is back.
Could the missing shield (which seems to be hard to get) be the cause of these issues? I have read Ogre's cave on this issue, but I am not good at manufacturing things like this shield.
Almost bald from tearing out my hair.
Help?
------------------ Life is good! Former President of the Georgia Fiero Club Now in Europe and driving a Fiero again!
Won't cause hunting idle but Missing PIM shield can cause several problems and even cause a fire. If you or others torque coils bolts w/o the sheild then you can crush the output pins to the coils.
Get Wells or AZ ICM and make a close copy of shied picture in the cave. Doesn't have to be exact. Dremel and a drill to rough cut it then file to remove shape edges.
------------------ Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should. (Jurassic Park)
PIM shield (original) and coils were replaced. Received an updated chip.........however.......Check Engine Light stays on constantly (sounds like it is permanently in diagnostics mode), fan runs permanentyl, high RPMs, regardless if warm or cold, extremely smells like unburnt gas and extreme low gas mileage. Will revert to old chip, even though the original symptom is gone (hunting idle) and it shifts really smooth. Can't pull error codes, as Check Engine Soon light will not go out.
Any ideas?
Thnx,
\D
------------------ Life is good! Former President of the Georgia Fiero Club Now in Europe and driving a Fiero again!
[This message has been edited by Donster (edited 03-03-2020).]
updated PROM? From where/who? Scam it if you can and see if ID number match prom note in cave. No match then maybe wrong PROM.
FWD cars use same ECM but program the PROM different so have VSS errors etc. Trucks DIS L4 often have different ECM and may take same PROM chip but if they work, have more errors then FWD cars w/ VIN R or U engines.
Correct Fiero PROMs listed in cave w/ final version in ().
OK, final update here on this issue (Thank heavens!): Correct updated PROM (From The Ogre's cave TSB - ATBW / 3531, .bin file from Dodgerunner) and all is good. Fun to drive again!
A special THANK YOU to the Ogre and all the others for their advice.
).
They're completely different.
