I have a 1999 Chevy Astro with 172K miles. The van has started to rough idle when in drive sitting at stop signs/traffic lights. It smooths out when in Park or neutral. Under acceleration, the van runs fine. Replaced plugs, wires, cap & rotor. Still have same problem. No codes are being pulled when checked.

Any ideas/hints/suggestions on what the issue might be?

Thanks.

 

Might be dirty injectors. The CFI sysetm is known to gunk up with time. You can try a Seafoam treatment into the throttle body. If that fails GM has some heavy duty stuff called GM Fuel System Treatment Plus, little pricey, but works great.

 

Sounds like sagging motor mounts

 

Air filter maybe.

 

I just swapped out the intake gaskets on my '02 and when I pulled out the distributor, the gear at the bottom of the shaft was heavily worn and introduced a lot of play. It confuses the ECM. I just ordered a replacement gear...seems to be a popular part to go bad.

 

SO did you ever figure it out?