Hi everyone. I am struggling with my daughters 87 v6-5speed. The car had been sitting in the garage for about 6 months with regular, every week or so start-ups. I did not drive it more than around the block so I did not notice when the current problem began. Here is the issue - The car runs well for the first 5 minutes or so after start when the battery has been disconnected, then when it is about at temperature the car begins to stumble and miss. Badly. If I disconnect the battery and wait a bit and then reconnect it, the car runs ok again for the same short time. What I have done so far- drained and refilled with fresh gas, removed and cleaned the Throttle body, changed the plugs, wires, distributor cap, rotor, Ignition Control Module, and today the entire distributor. It is running really well for the first few minutes, but then falls on its face. About 18 months ago I replaced the other Modules, EGR, EGR tube, and injectors. I don't know where to go next….I have no lights on the dash. Last weekend I saw a code for the Ignition Control module so I replaced it with a spare and then a brand new one. The light did not come back, but the issue remains. Just not sure what to do next- is this another module or maybe with the computer after it goes through the restart process. Any help would be much appreciated. I am running out of things to replace.
The computer is taking over engine functions and is getting some bad information. I agree that the CTS is the primary suspect, but there are other possibilities. Are you saying your instrument panel lights don't work or you have no SES light?
[This message has been edited by Gall757 (edited 02-16-2014).]
I think your problems are being caused by not giving the computer time to reset the engine after being powered down when you disconnect the battery. Try driving the car for 20 miles over 30 mph then turning it off for five minutes and then drive it again for another 20 miles, if you do this a few times the car should run better. If this doesn't help try some lucas gas additive you may have water or stale gas.
For what it's worth.....My '88 Formula ran fine for the first 5 minutes. Then after it warmed up it ran like Fido's butt because the CTS wasn't telling the ECM the correct engine temp. It ran rich and stumbled. Once I changed the CTS it ran great. Just my opinion.
[This message has been edited by Ventura (edited 02-16-2014).]
Originally posted by Dad: The car runs well for the first 5 minutes or so after start when the battery has been disconnected, then when it is about at temperature the car begins to stumble and miss. Badly. If I disconnect the battery and wait a bit and then reconnect it, the car runs ok again for the same short time.
It sounds like the problem temporarily goes away even if the engine is still warmed up, just from disconnecting the battery. In that situation, does it still run okay for 5 minutes, or does it drop to more like 30 seconds?
The ECM is always looking at the CTS. But it could still be the CTS, because when the ECM is in open loop (O2 sensor not yet up to temperature) it runs on the rich side. This could compensate for bad sensor readings, wherever they're coming from. You can test the CTS with a multimeter:
If that checks out, what happens if you electrically unplug the O2 sensor? MAP sensor? (1 at a time)
The sensor came in today and I just swapped it out. Reconnected the battery and the test drive showed the same problem. I have also noticed that the idle will fluctuate about 400 rpm say 1000-1400 after the problem starts. And it presenting itself under light throttle. If I push half way or so on the gas, she hesitates and then takes off and feels like normal. I am not sure what to try next. Fuel injectors, fuel filter (although having plenty of power when I give it throttle suggests it is not a delivery problem) maybe throttle body? She says she put in a bottle of fuel injector cleaner before it started, but I would think that would impact the filter. I don't know. I have no Check Engine light on and no codes. It is just running poorly. Anyone have any ideas?