engine misfire

[Hartman1]

I have a 95 avalon with a difficult problem to pin down. the engine misfires but only during the hotter months of the year, never in winter. It only happens when the engine is hot, I'm in drive with my foot on the brake. The next time I stop the mis may be gone and not appear again for another few days. I'm wondering if anyone else may have come across the same problem. any help is apreciated.

[aigochamaloh]

Any engine codes or CEL? How long since plugs have been changed? Air filter clean? Some basics to look at.

[wonger]

if you have a cel for the misfire.. than you might have bad plugs or wires

[Hartman1]

There are no codes, I recently got the car and pulled all the plugs, they look brand new. It has coil on plug and I checked the resistance of each coil.

[swiftjustice]

I would say plug wires based upon your description. They can break/short internally, look fine on the outside, and get dicey when they get hot.

[TMack409]

Originally Posted by swiftjustice

I would say plug wires based upon your description. They can break/short internally, look fine on the outside, and get dicey when they get hot.

Agree.

[Hartman1]

It's funny you guys say that beacause I thought the same thing last summer. I figured that the spark was leaking out of the boot down to the plug. NOw these coil on plugs arn't cheap so I decided I would try to just seal the boot with silicone grease. after doing that I did'nt have another misfire for the rest of the summer. But now I don't think that's the real problem, because the misfire has come back.

[TMack409]

Originally Posted by Hartman1

It's funny you guys say that beacause I thought the same thing last summer. I figured that the spark was leaking out of the boot down to the plug. NOw these coil on plugs arn't cheap so I decided I would try to just seal the boot with silicone grease. after doing that I did'nt have another misfire for the rest of the summer. But now I don't think that's the real problem, because the misfire has come back.

I'm sticking with *replacement* of the wiring harness and boots, not bandaiding.

[Hajoca]

Mist running engine with water in evening (low light ) and see if there are any stray sparks.

The Coil is usually encapsulated in Epoxy, when hot, a crack or gap may be large enough to cause that.

I have re epoxied several VW coils in the past with this problem.