1999 Buick Park Avenue 99 Buick intermittently runs rough

FIREFLYNJ

MEMBER
1999 BUICK PARK AVENUE
6 CYL
FWD
AUTOMATIC
206,000 MILES

Some times it runs great then there are bad days, weather has no effect. Tried, new wires and spark plugs, no help.

today it ran good at first, but after an 40 min drive it started missing right when it was going thru the state inspection center, and it passed!

ran bad the rest of way home, gets worse when trying to climb hill, I pressed the pedal down to push the car, ran real real rough, and service engine light came on.
codes I got were P0303, P0401, P0507 and P1404.

I took the EGR valve off and spayed it with carb cleaner. Didn't help car was still running rough after almost cooled off. Disconnected EGR 4pin connector, no change.

what else should I try?
there are times that the car has minor missing, which effects the trans not downshifting.

Thanks

3 Replies

JACOBANDNICKOLAS

MECHANIC
109,755 POSTS

Are you sure the EGR is good? IF you disconnected it and there was no change, it may be the problem.

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Wednesday, April 7th, 2010 AT 7:59 AM

FIREFLYNJ

MEMBER
3 POSTS

Follow up.
I didn't want to be buying new parts for this old car unless I sure it was the problem.

I was able to swap parts with another car, the EGR valve was not the problem, it was the coil pack/ECM, I found corrosion on the connection tabs between the coil and ECM, tried cleaning it but didn't last, I finally picked up a coil/ECM for $46 used and now running pretty good.

Thanks