QuestionIt started as a stumble/lack of power at low rpm’s, but it has been getting worse, it also seems to get worse with higher temperatures and humidity. I drove the car today, and for the first 15minutes it really wasn’t bad, it was just a slight stumble like it’s been most of the winter, but at about that point it started to get worse, mostly the lack of power began getting more severe and extending higher into the rpm band till it had problems maintaining speed at 50-60mph and idling it sounded like it was running on 2 cylinders, sounding like it was going to die (but did maintain a rough idle at roughly 1000rpm). I let it sit a little (and a rain storm passed) and when I restarted it, it was better, I was able to drive it on the highway at 60-70, but still sounded the same, stumbled off idle and sounded the same at idle.
There is no SES light, I can hear each of the injectors opening (listening to a screwdriver pressed up against them). I pulled the top cover and plugs, and none of them looked obviously bad, not fouled, a little lean and worn (to be expected with 100Kmiles), so I replaced the plugs with new ones and put it back together again. No difference. I will note that the ends of a couple of the plug boots were cracked, but there was no evidence of arcing or other problems. I haven’t checked fuel pressure, there are no fittings to do it at. In general, traditional diagnostics seem to be quite difficult on this engine.
The combination of ’95 last of the OBD1 setups, OBDII style connector and one year only ECM has prevented me from coming up with something to properly scan the thing (don’t have access to a proper tool like a Tech II and haven’t had any luck with the dealer telling me what’s wrong). I’m getting a bit stumped at what to check next without just throwing parts at it.
If I was going to guess my top suspect is a problem with the ignition module or some other bit in the ignition since those traditionally can be affected by both temperature and humidity, but I can’t find any real documentation how the ignition works or how to diagnose it’s parts. Otherwise, most sensors that could cause this sort of running should set a code, as should fuel pressure low enough to cause this kind of running.
Any idea what it is/how to figure it out?
AnswerHey Mark:
I agreee it's an ignition system issue. Being that it's an OBD system it doesn't have the ability to store misfire codes and misfire data which makes it harder to repair than a obd II system. The most likely cause for this would either the boots you were taking about being cracked. The other thing that happens with that engine is the cover that the coils and ignition module is prone to cross fire inside the cover. meaning the coils cross fire between each other instead of firing the plug. You can hose down the engine and start it up an listen for spark arching under the cover. if it is misfiring and you can hear it arching it's more that likely the boots. if it's misfiring and you can't hear it arching it's inside the coil housing.. If this isn't a spark issue then I would look further into things like fule pressure or a bad ground wire for the ECM. that engine was prone for ground wire issues on the lower engine to transmission mounting bolts. the wires would either corrode or would brak off. take a llok at them and give them a tug and see if any of them break off. There is also on on the block near the oil filter. good luck :)
One other though that car had a recall on it for corroded ecm/wiring to the ecm. any dealer can run your VIN# to see if the recall was ever done on it. That recall if it's not been done can cause all kinds of goofy driveability concerns.
