Thread: Miss While Accelerating

Car is a 2000 GP Just rolled 142K

Car runs great at idle & while revving in neutral.
No Check Engine Light (which leads me to believe it isn't a coil pack, especially since it doesn't miss at all times, been there done that)

It has a miss while accelerating(under load). The quicker you accell the worse it does it. Seems to correct itself when you get up to speed.

It also seems worse after it sets idling for a period of time.

I pulled the plugs to check for anything out of the ordinary, they seemed a lighter color than usual. But no deposits, cracks, etc. Wires are good and fairly new. Car is always maintained at proper intervals by myself.

Sorry for the long rant, just trying to be as thorough as possible.
Any and all input is appreciated. Thanks

what size motor?

Originally Posted by Seansta

what size motor?

3.8 Naturally Aspirated

As for the cat, I will give that a try tomorrow.

cam lobe wore flat, burnt valve,weak valve spring, bent pushrod ---do compression check with all plugs removed* possible routing of plug wires near a electrical harness more so in wet or dry weather? coil pack may be weak also, won't work under heavy load....

mass air flow sensor .. remove boots from each end look at small diodes on inside , if black or just dangling around replace it, start engine , tap mass air flow sensor with screw driver handle if it stumbles or quits replace it

Well..I checked everything that had been recommended to me. Didn't cure it. Went out and got it up to operating temp, then pulled it in the shop & removed the engine cover. Found some moisture around my rear valve cover area. It seems to be what I was hoping it was not. LIM gaskets.

Odd thing is, there is no coolant noticeable one the dipstick. Oil is clean and clear, not milky. No smoke or sweet exhaust fumes. Just some moisture under the fill cap.

There was so much crud in there, circled in the pic that it was breaking down the aluminum of the lower manifold.