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89 runs, shuts off, then won't start

Old 11-08-2018, 01:42 AM
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AudioObsessions
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Default 89 runs, shuts off, then won't start

Hey all, my 89 will start and run for about 20 minutes and then die. I have already replaced the ignition control module(twice), changed fuel filter, cap, rotor, plugs, and wires. After it dies I do have spark(tested using a timing light) and fuel pressure. If I let it sit for a few hours she will start again. It does have a low temp sensor to have the fans come on at 190. I watched and even after the fans came on at 190 the running temp stayed at 188-192 for about the last 10 minutes. This was all at idle, I have no brakes so I have not been able to take her out for a spin yet. Now, I know I should be able to let this car sit and idle for hours and not have this problem. When I replaced the ICM, I made sure to coat the underside with the grease. I find it hard to believe that 2 modules in a row would be bad. When it shut down the previous night, temp was around 205 because I would rev her up every now and then. I'm baffled, any ideas? I have a FSM on the way, just not here yet. I also have a set of Bosch 3 injectors on the way from one of the forum members, but could it be the factory injectors? It seems to me that it is some sort of temp issue as it runs fine as long as it's a cold start. Let me know what you guys think and if there is something else I should test(might also want to include how to test it, lol). Thanks guys and gals.
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Old 11-08-2018, 01:49 AM
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VikingTrad3r
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can u describe how it dies?

like does it cough sputter then die a long death or is like somebody turned off the ignition key
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Old 11-08-2018, 01:50 AM
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84 4+3
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Spray starting fluid in the throttle body when it wont go. If it does and then stays running it's the injectors. Only spray a little... doesn't take much. South main auto has a detailed video on testing the C4 (tpi) injectors with an ohm meter. My cousins car did this. Idled okay and revved fine but driving was horrible and it had hard starting problems. It wasn't a hard 20 minutes but it was fairly close.

Last edited by 84 4+3; 11-08-2018 at 01:51 AM.
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Old 11-08-2018, 02:07 AM
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AudioObsessions
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Originally Posted by VikingTrad3r View Post
can u describe how it dies?

like does it cough sputter then die a long death or is like somebody turned off the ignition key
It's as if someone just turns off the key. I will try start fluid tomorrow evening and see if that works after it dies. I'm going to look up the video on testing the injectors now. Thanks!
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Old 11-08-2018, 12:48 PM
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Originally Posted by ihatebarkingdogs View Post
If it still has its original Multec injectors: The injector coils degrade from the ethanol in the fuel. The resistance goes down as the coils short out internally. The current that the ECM has to sink to control them increases. The ECM overheats, and the internal circuitry shuts down, but once the ECM cools, it will run again. This is kind of common on the 89-92 Multecs, although most of them have been changed out by now on the cars that are still on the road.

You can check each injector with an ohm meter. I don't remember the exact value offhand. Something like 14-17 Ohms. Check them all, and if some are much lower than the others, you've identified the problem.
Yep! Tested and I have 2 bad injectors. Good thing I already have a set of Bosch on the way! Thanks all. I'll update this thread if that for some reason does not fix the problem.
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Old 11-08-2018, 02:08 PM
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Hope these videos help !!.....INJECTORS !!!!



Last edited by rwobs777; 11-08-2018 at 02:11 PM.
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Old 11-08-2018, 02:15 PM
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Originally Posted by 84 4+3 View Post
Spray starting fluid in the throttle body when it wont go. If it does and then stays running it's the injectors. Only spray a little... doesn't take much. South main auto has a detailed video on testing the C4 (tpi) injectors with an ohm meter. My cousins car did this. Idled okay and revved fine but driving was horrible and it had hard starting problems. It wasn't a hard 20 minutes but it was fairly close.
Just posted that video....if you ever need help I'm in Monmouth County !!
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Old 11-08-2018, 04:04 PM
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Originally Posted by rwobs777 View Post
Just posted that video....if you ever need help I'm in Monmouth County !!
Yep, watched those to prep myself. Thanks for the assistance offer!
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