Reading all the pages and seeing lots of info on missfires. None seem to fit my scenario though. On a cold start, seemingly damp weather only, the truck will start and idle extremely rough. When put in gear the truck will buck/shake violently with no power, bogging under throttle. Once the eng warms it smooths out and runs normal. The problem is intermittent only. Plugs, wires, cap, rotor all replaced. Seemed to occur after the cap was replaced, so I replaced it again with no change. Could there have been a sensor damaged when the cap was changed? Any info appreciated.

 

Are there any codes stored? what year is your truck? motor size?

1st place i'd look would be the IAT sensor, then the o2's. it sounds like it may be too rich when it's cold and the IAT measures the intake temp. I'll take a look at the manual to see if a short could cause an overly rich condition... but sounds like your running too rich.

 

never had it checked for codes. would the codes come up a general missfire, or more specifically to a sensor, etc. truck is a 1995 w/5.2

 

check your coolant temp sensor, I'll be it's open when cold. just looked at the manual and it says that the ECT sensor is used to control injector pulse width during open loop mode while the motor is cold. all the other sensors appear to be bypassed until it's at operating temp. if the sensor is open when cold then the pcm will have a hard time adjusting the injector pulse width so it will run correctly...

 

I'm not sure how to get the codes out on a '95, you might try the key on-off-on-off-on method and look at the number of flashes the check engine light gives. a 2 second pause between flashes means it's on the next digit of the code... you should get a book on it to see what the codes mean.

 

thanks for the info.....question.....if the ECT sensor was bad, wouldn't the problem occur on all cold starts?

 

it could be intermittant.

 

On my 95 ram there is an obd 1 connector on the main wiring harness on the firewall. If you have access to a scanner you could check for codes easily but if not you could count the flashes and look the number up in a troubleshooting book w/ diagnostic codes.

 

so the key thing works on your '95? (on-off-on-off-on)

 

I'll let you know after lunch..........