4g61t.org

Fortunately I was only about a half mile from home when this happened.

The engine died, no warning, just quit. Quick check revealed no spark. More in depth check found all the wiring OK, power transistor not firing the coil, ECU not triggering the power transistor. Checked for a signal at the ECU, none present. Injectors operate OK. Checked the capacitors inside the ECU, minor leakage but no deterioration of the PCB. Could the leakage cause the no-crank/no-start condition if the PCB is OK?

Aside from that, I'm thinking dead ECU. If anyone has any more ideas as to what to check, let me know. Thanks.

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Witty Signature Goes Here!

Is it an 8v or 12v?

The 12V engines are notorious for trashing the cam angle sensor which is in the distrubitor. Water/crap gets in the and screws them up. Take one apart and you'd understand, it's a pretty dumb setup. Might want to try that out as well.

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Darin
1986 GMC 3/4 Ton 4x4 Diesel (soon to be Greasel)
1993 Colt GL

Can you elaborate? I havent heard that...

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http://members.cardomain.com/socrateez
04' Olds Alero
91' Colt GL hatchback
4g15 12valve 5spd.
4g37 TB, MAF & Injectors. 4g37 ECU
Ported & polished & custom CAI w/K&N filter
5* Cam retard, 7*Ignition advance
2-1/4" catback w/flowmaster muffler
89 GT brake and suspension swap
Lots of little s#@t

Kyle, I had the same problem with my dead ECU back last fall. Engine did give warning signs that something was wrong though;
Idle wander,
Hard starting and general malaise from the system.
My PCB was fine for the most part but too much damage had been done to the injector drivers in the ECU to resurrect things ie. caps.
I checked everything in the whole circuit just like you have from plugs/wires/injectors/distributor/power to distrib. etc. the only thing left was no signal going to the distibutor to fire the coil and such. I even checked resistances at the coil and the other wires all the way to the ECU, I had no options left by the time I was done. Sounds very familiar to me.
If you need a spare 12v ECU let me know .... I've got one needing caps that a fellow user (PMA1123) assured me was running like a top until it was pulled 6 months ago. As I'm sure you aware he's a member in extremely good standing IMO.
Tim

It is an 8v.

I assume since the injectors are firing as they should, the CAS/TDC sensors are properly sending signals.

Tim - That's the weird thing about my ECU. While there is leakage, there is no conductor deterioration, so I can't 100% blame this on the caps. There also was no perceived warning sign, just the sudden heart attack (or would brain aneurism be a more appropriate analogy?).

I assume 8v and 12v ECUs are not compatible?

EDIT: If someone has a 4g37 ECU laying around, I could use one of those as well. I still have the MAF and injectors from my wagon, so I can swap over the entire set.

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Okay, put in the known good ECU from chdesign (thanks again!). After clearing out the flooded cylinders, the engine fired right up and as soon as the idle re-adapted it idled equivalent to previous to the ECU failure.

However, now it won't run well at part load. Idle is OK, high load is OK. Part load it bucks and sputters and runs like overall crap. It doesn't seem to be relative to throttle position or engine speed, but I'll check the TPS tomorrow to be sure. I didn't move any vacuum lines during the original diagnosis.

Any other ideas???

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this may sound silly but have you rechecked your timing marks? When my ECU was on its way out and i didnt know it, I got the car to run but it was also bucking. I think thats when my belt slipped causing...well you know. But I also dont know how loose or tight the belt was to begin with.

I had similar problems with mine before i pulled it. I decided to do the general maitenance, wires, cap, plugs, filters, injector cleaner, engine flush and rad flush, after that the beast came to life. I remember beating a civic that day, he had an exhaust and he was by himself, i was with a lady friend and i smoked him to 3rd gear then traffic....
enough blabbing, just my $.o2

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92' Dodge Colt 200GT - 4G63T - Taking Offers.

I didn't have the engine running more than a few minutes, and there were no running issues before the coil trigger circuit in the ECU went dead. That, and the fact that it runs OK at idle and WOT, but nowhere in between, makes me suspect of the TPS. My plan (if I don't set fire to this car first, that is ) is to replace the T-belt and tensioner shortly anyway.

If it isn't the TPS, I'll try a new set of spark plugs as I recall having serious running issues on a Nissan pickup after the engine flooded, even with thoroughly drying out the plugs.

Almost looking into a new vehicle, maybe a Lancer Ralliart wagon...

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Replaced the plugs, still runs like crap. It's running super rich judging by the condition of the plugs (dull black and moist) and plume of black smoke exiting the tailpipe.

This could be something, or it could be nothing. According to CAPS, production dates from 4/88 to 5/89 uses a different part number than 6/89 to 5/90 8v engines. I have one from the latter date breakdown; my car is 4/88 production. Has anyone else encountered this problem with swapping ECUs? I thought all 8v 4g15s were created equal.

I'll check the temp sensor (of course), but aside from that, ???????

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Keep in mind, a bad TPS can ruin a perfectly good ECU too.

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Geoff
2013 Genesis 5.0 RSPEC
88 Mazda Turbo II- LSX7
89 2.0 Turbo Colt
13 Ducati 1199 Panigale

The tps test is pretty easy is it not?

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89 Mighty Max 2.6. Lookin for side drafts 89 Colt turbo. SOLD
91 Galant GSX, waiting for 2.4

The TPS is OK. I forgot to mention I checked it out.

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i would say your problem definatly lies within the fuel delivery. it wouldnt make sense that it would only spark incorrectly in midrange. being that said have you checked your o2 sensor? if your o2 sensor is telling your computer theres too much o2 in your exhaust then its going to dump alot of fuel and only run right at high rpm were more air is going to compensate for the excessive fuel.. donno just a suggestion. my bucking and cold start problem was because my o2 wire was loose and upon putting it the temp sensor i noticed it. then i returned the sensor and fixed my o2 wire and it starts and runs great.

I see what you are saying, but when the engine is cold the o2 sensor is "off-line." The engine runs in open loop until the oxygen sensor starts sending an appropriate voltage, meaning that the engine runs on a set table of values and does not fine-tune ignition timing or fuel curves.

I tried to check the coolant temperature sensor with a crappy Chinese analog voltmeter, all it told me was it does not have an open circuit. I'm going to bring my good digital DVOM home from work and double check it. Even if that analog meter was in the vicinity (or even the same area code, for that matter) of being accurate, the CTS was reading a lower resistance (hotter temperature) than it should have on a 40-degree night. I also tried shorting the connector pins for the CTS to fake the computer into thinking it was running around 240 deg. F, but it did little to nothing to lean it out to where it should be. I'm ruling out the CTS fairly quickly.

I also checked the FPR to make sure there wasn't a torn diaphragm letting fuel in through the vacuum line, that checked out OK.

So what else do we have here that affect fuel injector pulse duration that has not already been checked.

- IAT
- MAF (hyperactive - indicating more air than actual? is it possible?)
- Baro
- O2 sensor (not reaching operating temperature given short time running; should have no effect?)
- Battery voltage to ECM (lower voltage = longer injector pulse to compensate)
- ECM production date / part number breakdown (can someone confirm or disprove this please?)

I'm still trying to figure out why whatever has gone bad, went bad. As I said, the engine was running perfectly up to the point that the coil quit firing. Now with the new computer the fuel delivery is overactive.

Car rentals are getting expensive. I need to make this thing run right like now-style or go buy something else on a monthly payment plan.

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