86 running like poop
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Joined: Mar 2003
Posts: 57
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From: Chesapeake Va
86 running like poop
This is a friend's car. Last week, it ran fine, parked it, next time he started it, wouldn't stay idling. He bumped up the timing to keep it running, checked for obvious electrical connections and vacuum leaks, couldn't find any. I scanned it with my ez-scan 5000, and had some interesting results. While sitting parked, idling, it shows a vehicle speed of between 1-5 mph. It shows RPMs between 300-6000, while it's idling about 650 or so. It doesn't seem to be getting any reading for Idle Air, EGR, Throttle sensor, or Mass Air Flow. Knock sensor is constantly going up. The Manifold Air Temp is showing a -13 degrees or so. I also noticed the PROM ID seems to keep changing. I triple checked all the connections from engine to computer, everything seems fine. I also triple checked to make sure scanner was configured properly. I've used the scanner on many other cars and never seen anything like this. I even checked it on my 96 to be sure it was working properly, and it is. Does this seem like it could be much of anything other than ECU/Prom related?
Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
If all these are way out of range like you say and it happen at the same time I would think ECM. But there is a way to troubleshoot before throwing another ECM in there. Do you guys have a 86 FSM?
Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
The 85 FSM should be very similar as far as troublshooting. Try testing some of the easier ones first...like MAF. If you follow the chart down to where it says replace ECM then try troubleshooting a different sensor and if the same then I'm leaning towards the ECM/PROM.
Maybe someone else will give some suggestions too!
Maybe someone else will give some suggestions too!
Instructor
Joined: Apr 2002
Posts: 249
Likes: 0
From: Broken Arrow Oklahoma
Tell the scanner the car is an 87 and that should fix your problem. Any time you use one of those scanners and the prom code is rolling you haven't hooked properly. It's a fault of the scanner not the car.
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Instructor
Joined: Jun 2006
Posts: 194
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From: Hartselle Al
My suggestion is this:
Unplug the Battery. Unplug the ECM. Take out the Chip. Put the chip back. Put the ECM plug back in. Plug back the battery. During all this check connections. I once tracked one down and it was one wire pulled away from the ECM plug harness. The ground if I remember correctly. Long-ago.
I also used a volt-ohm meter to confirm voltage and connections to the ECM.
Unplug the Battery. Unplug the ECM. Take out the Chip. Put the chip back. Put the ECM plug back in. Plug back the battery. During all this check connections. I once tracked one down and it was one wire pulled away from the ECM plug harness. The ground if I remember correctly. Long-ago.
I also used a volt-ohm meter to confirm voltage and connections to the ECM.
Intermediate
Joined: Mar 2002
Posts: 48
Likes: 0
From: Naugatuck CT
I tried this today on my 92 LT1 - when I started it yesterday, it ran like one cylinder is not working, but there were no codes other than the normal C12. So, I disconnected the battery, unplugged the ECM, pulled the chip and put everything back in reverse order - no difference.
I didn't check the pull the spark plugs yet. That's next. Any ideas?
Sorry that this doesn't help the '86 problem, but I agree with you that unplugging and re-connecting is a good, quick and cheap thing to try - 'just make sure you are grounded for static electricity before touching the chip or any connector pins.
I didn't check the pull the spark plugs yet. That's next. Any ideas?
Sorry that this doesn't help the '86 problem, but I agree with you that unplugging and re-connecting is a good, quick and cheap thing to try - 'just make sure you are grounded for static electricity before touching the chip or any connector pins.