Author Topic: Engine miss only when warmed up (Read 3516 times)

naika · « **on:** January 24, 2009, 03:41:46 PM »

hi,
I just replaced all my intake gaskets, valvecover gaskets and also cleaned up the "mess-under-the-intake" I double checked everything and I'm 99.9% sure everything is in it's place.
I replaced the spark plugs and some other service (oil, filter, etc.)

When I start the car, it runs fine, idles fine with a cold engine. Then, I go and ride for a couple minutes and the car starts to have some miss at steady speed on the highway. If I stop and get back in 1st, it seems like it runs on 3 cyl. but only for a couple seconds and goes back to normal.

I thought it could be a bad plug wire or ignition coil? what do you gyus think? anybody had this happen before?

Before I took the car appart it seemed to run fine but it could also be that taking the plugs out and all would have damaged a wire??

Any ideas?

Thanks guys

twright · « **Reply #1 on:** January 24, 2009, 04:16:20 PM »

These engines are real particular about the type of spark plugs you put in them.

Put the old plugs back in and see what happens.

naika · « **Reply #2 on:** January 25, 2009, 05:21:45 AM »

Quote from: twright;65296

These engines are real particular about the type of spark plugs you put in them.

Put the old plugs back in and see what happens.

It did that before I replaced them, and the old ones were older than me. I installed NGK plugs, the factory recommended part number, so I doubt it would be the problem. I lean towards a plug wire but would it act up only when engine is warmer?

twright · « **Reply #3 on:** January 25, 2009, 07:54:34 AM »

Yes. My M42 had a very intermittent missfire when the engine was warmed up. It never missed when it was cold.

I changed the ignition wires and it doesn't miss now.

The fuel mixture is higher when it is cold. That must cover up some ignition problems.

tjts1 · « **Reply #4 on:** January 25, 2009, 01:20:21 PM »

I had the problem right after I replaced my spark plugs. Ran fine when I started it up, engine warmed up and after a few minutes on the freeway the engine would miss or lose power repeatedly. It turned out to be my very old and very worn out spark plug wires. I think moving the wires around to get to the plugs was the last straw and one or more failed internally. I replaced them with some used (less used than my factory originals) volvo 850 wires and all was well.
good luck

Boosted E30 · « **Reply #5 on:** January 25, 2009, 01:55:39 PM »

i had this with my car as well but it would only happen warm and when you took off from a stop after changing everything else possible i did the wires and problem was gone.

You can check them just get a spray bottle with water and with the engine running spray your plug wires and look for little blue sparks either arching to another wire or the valve cover. they are kind of hard to see so you have to really look to see them. if you do see them then you know thats your problem.

naika · « **Reply #6 on:** January 26, 2009, 11:46:07 AM »

Thanks guys,
Since i Took the wires out to clean them and replace the heatshield I must have moved them one too many time for the age.
Everybody seems to agree that it is the problem so I'll be looking for some wires.
Are the Volvo 850 wires similar? that's pretty interesting.

Thanks again

naika · « **Reply #7 on:** February 09, 2009, 03:08:10 PM »

UPDATE: I just did my COP today, made my own plate out of Stainless steel sheet, I secured the coils with self-tapping screws and it feels really solid. I only need to run the wires a bit better and shorten them but the car runs perfect, It cost me €50 for 6 Bremi coils 11 860, and a couple bucks for the studs and such.