car runs ****ty in park

1fast6

Active Member
Joined
Aug 2, 2010
can't figure this one out. car idles rough in park. sounds like it has a big cam in it.
put it in drive and it smooths right out. vac is low in park, about 10''.
cruising and let off gas pedal vacuum will go to 18''.

blm is 120 at idle. fuel pressure is 42#.
idle fluctuates in drive with foot on brake about 50-75rpm's

haven't done a compression check yet. Also hear some slight ticking coming from pass vc. need to pull cover and check rocker arm shaft.

any other ideas let me know. thanks
jeff
 
can't figure this one out. car idles rough in park. sounds like it has a big cam in it.
put it in drive and it smooths right out. vac is low in park, about 10''.
cruising and let off gas pedal vacuum will go to 18''.

blm is 120 at idle. fuel pressure is 42#.
idle fluctuates in drive with foot on brake about 50-75rpm's

haven't done a compression check yet. Also hear some slight ticking coming from pass vc. need to pull cover and check rocker arm shaft.

any other ideas let me know. thanks
jeff

mine was the o2 sensor and iac reset. i put in 2 gm purple wire and it would run rough in park and smooth in drive fought this problem for years. ended up putting in a denso and now it is smooth in park and the 02's are 830 to 850 in park with the gm it was 550 to 650 in park. also did a iac reset.
 
Do you have vac brakes? Could be the booster leaking vac until you step on the brakes. Kind of a longshot but it's the first thing that comes to mind. If vac is low in park then look for vac leaks. Though depending on setup and engine condition, 10" is not terribly low. It is lower than a stock car should be from what I have gathered.

Blms are level but you may have open loop idle depending on setup. Also clean your IAC and verify the iac is working properly and that the tps/throttle blade stop screw are set proper.
 
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