Rough running 85

[Richard F.]

I have a 14,000 mile 85 that runs very rough with the following conditions:
Voltmeter shows 12 volts with key off and 14.5 volts running. When the car is running cold its OK, but as soon as it gets warm, it begins to run very rough and sometimes the voltage on the gauge cluster jumps to 15 to 19 volts and oil pressure 100 psi. However, during this time, the voltmeter clipped to the battery still shows 14.5 volts. Also, during this spike, the interior lights do not work. The scanner showed code 12 (TPS) and I changed and checked it. Subsequent scanner check showed that the ECM was in "limp home mode" with no data available and no codes so I changed the ECM. You guessed it, NO change! I'm lost at where to go next. Has anyone out there had this problem or can advise me where to go next?

[Edward J.]

Re: Rough running 85

Rich, code 12 means nothing when doing your dia. with key on and engine not running. if you are receiving code 12 with car running this means missing tach. signal. It has been a while since I have seen this code. As far as the gauges it surly sounds like a problem with the cluster. If the voltage is 14.5 with a meter attached to battery that is okay. Just be sure to check the battery voltage with the RPM's at about 2000/2500 and see what the voltage is. Normal voltage range should be about 13.8 to 14.5. If it was indeed at the 15+ range that could be a real problem as the computer could not handle this type of load and would fry the some of the computer boards internally. The biggest problems with the C4 's of that vintage is lean fuel injectors. especially if they are the originals. First make sure you check for vacuum leak, like a vacuum hose off. and timing check, spark plugs, ignition wires. Its really tuff to make a dia. via discussion. Sometimes we can steering you in the right direction but a scan tool and the right equipment makes life easier.

[David H.]

Re: Rough running 85

Seems like the problem occurs when the car transitions from open loop to closed loop fuel injection as it warms up. What do the O2 sensor connections look like (corrosion)? Have the O2 sensors been changed? Any corrosion/pin damage on the ECM connector? Corrosion on engine bay grounds?

[James W.]

Re: Rough running 85

Richard

id check my grounds. Lots of crazy things happen when a ground wire gets loose

jim