Rough engine at idle in park or gear vs. Neutral o.k.

[JHZR2]

my mother's 97 plymouth breeze does the same thing... only the shake goes threough the steering wheel.

Ive been told it is that the engine is minimizing power at idle to keep fuel use low.

JMH

 

[Eddie]

First clean the throttle body before anything else. Then a good tune up with spark plugs/air filter/fuel filter? and check the hi voltage leads to the plugs. Most computer controlled engines set the idle via computer so messing with any idle control screw can mess things up.

 

[punisher]

Something as simple as a small vac leak will also cause those symptoms. Good advice above, check mounts, throttle body and IAC and verify engine idle is at spec.

 

[doitmyself]

Thanks everyone,

I will look into all of your ideas. A mechanic friend of mine (mostly GM's) guessed that it might be an eletrical/mechanical "throttle advance" designed to change the idle speed when stopped in park or gear.

This is actually a "new" used '99 Escort my son bought to replace his other one (totaled by idiot driver). It's in almost mint condition, but may have sat around for a few months. We are in the process of going through it - tune up, fluids, etc..

Thanks again for the ideas.

 

[doitmyself]

My son's '99 Ford escort runs like a top. Except, when you are at a stop and it is in park or in gear with brakes applied, the engine idles very rough.

If I stick it in neutral, then it smooths out. I can't figure out if it is the engine or the transmission. It feels like the transmission is "dragging" on the engine when stopped in gear or park. It doesn't seem to be a spark plug mis-fire, but who knows.

I have seen a bad motor mount cause this and sometimes a vacuum leak.

ANY OTHER ADVICE??? How to diagnose??

Thank you.

 

[drive it forever]

"doitmyself", save yourself a headache and have a mechanic look at it? Is the idle too low?

 

[Chris142]

I'd guess that it has a worn mount. When in gear the engine moves just enough to allow the vibration. In neutral the engine doesnt move.

Another possibility is a dirty or gummed up throttle body or IAC motor causing a low idle.