My 87 GT has been running very rich at idle. It doesn't set a code or run rough, but the exhaust odour is very strong. The ECM data shows that the INT goes up significantly at idle and goes back to normal when driving normally.
It's a 3.4 P/R with the stock ECM and custom chip from sinister performance. The same scenario occurs with the stock chip. Any ideas on what I may need to replace to fix this problem?
what about scorn/ worn fuel injectors like leaching to much fuel into the cylinder? sounds like the problem i had with mine when the injectors were not seated right. and the pintle was pushed in on the injectors the pintle is the little pin that sticks out the tip of the injector. any ways a scorn or worn injector will do the same thing.... junk in the fuel ware out the injector over time and they leak... it like using sand paper on the inside of the injector...
Still having problems with this unfortunately. Tried installing a heated o2 sensor, but that didn't turn out to be the fix for this particular problem. Adjusted my fuel pressure to 43.5 psi. Turns out it was set a lot higher than it should have been because the fiero store pressure gauge doesn't read accurately when it is hot.
With the A/C on I had puffs of smoke coming from the exhaust which had a very strong odor. Without A/C it would still be strong but with less smoke. If I jumped the A-B ALDL terminal the smoke would disappear as well as the odor.
Looking at my sensor data in my original post I still cannot work out what would cause that to happen.
Can anyone offer any further advice? I'm thinking about changing my fuel filter next, but I'm not sure that would improve my rich condition at all.
You have shown that the problem is with the ECM data when you jumper the ALDL and the problem goes away. You have replaced the CTS and the 02 sensor, so next I guess I would electrically disconnect the MAP sensor. One of those sensors is throwing off the ECM, or the computer itself is bad (unlikely).
How is the Coolant Temperature Sensor reading? I've had them go bad without setting a code. They have usually defaulted to the cold or rich side of the scale. My first one that failed was showing the coolant temp to be -28 F., the car would hardly run, and it didn't set a trouble light until I unplugged it.
What injectors did you use? Did you go with the stock 3.4 Multech injectors? Sometimes they present difficulties when used with the Fiero ECM.
You can also check it's accuracy with a multimeter using this scale. You'll need to determine the approximate temp of the sensor.
I looked at the log but I didn't notice anything clearly wrong with it. The log doesn't include the flags so it doesn't actually show whether it was running in closed loop, but I presume it was. Coolant temperature readings look normal. It was trending upward the whole time though and got to 227F near the end - not a problem but it looks like you're using the factory fan switch. If so, you might like the 210 on/200 off switch that Rodney Dickman sells. (Not relevant to your question though.)
IAT looks normal.
The first idling period in the log shows MAP in the low 30s kPa. Log doesn't indicate if trans was in gear but assuming it was out of gear, then this looks normal. All idling periods after that show MAP in low 40s kPa. This is normal if it was in gear, but if it was out then it's high. That's only based on comparison with logs from my car.
The O2 sensor seems happy with the mixture. I'd suggest replacing it but you already have. Do you have any exhaust leaks? That could be tricking the sensor. Not sure why jumping the A-B connector is helping. I don't know what all effects that has. The one effect I know of is that it locks the timing at base timing, so you end up more retarded than usual. Usually it's about 18BTDC when idling (or more accurately, distributor setting +8 degrees). So the jumper would effectively take 8 degrees out of the idle (=10BTDC if distributor is in factory position). I suppose that puts more heat in the catalyst, and maybe overall less fuel ends up being used due to the O2 sensing less efficient combustion.
Turning on the AC increases the load = more fuel used, but I don't know if that should translate to a stronger odor at the exhaust outlet.
Does this car have a working catalyst? I don't know if it might be normal for it to smell very rich without a cat, even if the mixture is correct. I've always had a cat.
Originally posted by James_GT: I inspected the ground connection on the left side of the engine block and it looked fairly dirty. (see image below). I sprayed it with lots of electrical contact cleaner and went for a test drive.
I would remove that bolt and re-crimp the ground wires. It looks like your spray cleaner is the only thing completing the ground.
I had a go at repairing this problem myself a few days ago.
Found the bolt in the picture above wasn't particularly tight. I removed it, cleaned it and the ring terminals. And finally I covered up the exposed wire with electrical tape as I do not have the replacement ring terminals yet to re-crimp it to. It's still connected properly, just missing a bit of its insulation. Not sure if this would affect the ground connection or not.
Since then, the exhaust odor has reduced significantly. I'm not entirely sure if that has fixed the problem or its just a coincidence, but for the last few days I haven't had a problem with it. So I'm assuming it must have had some part in the rich condition the car has had for the last year or so.
Well worth the effort to clean and tighten all the ground connections on the Fiero, as they can really cause some irritating issues if they're not functioning properly.