86 running erratic but no diagnostic codes
Thread Starter
Burning Brakes
Joined: Jan 2005
Posts: 1,239
Likes: 4
From: Shelby Township Michigan
86 running erratic but no diagnostic codes
Hello, my 86 is running very erratic with the check engine light coming on at random but I don’t get any diagnostic codes from the ECM. Check engine light will just flicker when I try to get the codes. Car will start and stall or not idle but sometimes it idles fine and then touch the gas and it dies. Upshift arrow lights up when sitting still in park at random, when the check engine comes on while driving it’s like the car lost half its power. Car is bone stock with only 36k miles on it. Does this sound like the ECM is bad? Car has fuel pressure and spark. One minute it’s running fine and then I go to pull into traffic and if falls on it’s face. Thanks for any help.
Advanced
Joined: Apr 2022
Posts: 67
Likes: 9
Starting with the basics
Would focus on electrical issues as "flicker" is noted
--take off, clean and reattached all grounds and power supply wires
--if any in question--add additional wires as "testing wires"--remove at later date
--inspect all connectors--pull apart and re-attach--start and run car at every change--need to isolate exact locaton
--perform "wiggle test" of wires, wire harness and connections--
--disconnect one input sensor at a time, CTS, TPS, MAF/MAP, O2 etc and drive car--car should run--most likely "rich" and set corresponding code for sensor--
Keep all posted
Would focus on electrical issues as "flicker" is noted
--take off, clean and reattached all grounds and power supply wires
--if any in question--add additional wires as "testing wires"--remove at later date
--inspect all connectors--pull apart and re-attach--start and run car at every change--need to isolate exact locaton
--perform "wiggle test" of wires, wire harness and connections--
--disconnect one input sensor at a time, CTS, TPS, MAF/MAP, O2 etc and drive car--car should run--most likely "rich" and set corresponding code for sensor--
Keep all posted
Thread Starter
Burning Brakes
Joined: Jan 2005
Posts: 1,239
Likes: 4
From: Shelby Township Michigan
Starting with the basics
Would focus on electrical issues as "flicker" is noted
--take off, clean and reattached all grounds and power supply wires
--if any in question--add additional wires as "testing wires"--remove at later date
--inspect all connectors--pull apart and re-attach--start and run car at every change--need to isolate exact locaton
--perform "wiggle test" of wires, wire harness and connections--
--disconnect one input sensor at a time, CTS, TPS, MAF/MAP, O2 etc and drive car--car should run--most likely "rich" and set corresponding code for sensor--
Keep all posted
Would focus on electrical issues as "flicker" is noted
--take off, clean and reattached all grounds and power supply wires
--if any in question--add additional wires as "testing wires"--remove at later date
--inspect all connectors--pull apart and re-attach--start and run car at every change--need to isolate exact locaton
--perform "wiggle test" of wires, wire harness and connections--
--disconnect one input sensor at a time, CTS, TPS, MAF/MAP, O2 etc and drive car--car should run--most likely "rich" and set corresponding code for sensor--
Keep all posted
Instructor
Joined: Oct 2000
Posts: 190
Likes: 10
From: southern new jersey
You need the factory service manual and there is a procedure. Mine is an 86 as well with only 12,000 miles. It was running like crap and doing weird things, flashing the SES light and only a couple of times actually set a code. Then the code went away after I saw what it was. Then it would flash the SES light several times without setting a code. Going through the test procedure for the code that it presented the one time it came down to a bad ECM. Changed the ECM out with one out of an 87 and all has been well.
Thread Starter
Burning Brakes
Joined: Jan 2005
Posts: 1,239
Likes: 4
From: Shelby Township Michigan
You need the factory service manual and there is a procedure. Mine is an 86 as well with only 12,000 miles. It was running like crap and doing weird things, flashing the SES light and only a couple of times actually set a code. Then the code went away after I saw what it was. Then it would flash the SES light several times without setting a code. Going through the test procedure for the code that it presented the one time it came down to a bad ECM. Changed the ECM out with one out of an 87 and all has been well.
