It only missfires when you put load on it IE; passing or going up hills, but other times runs smooth. The engine has about 175,000 on it, has new plugs, wires, coils, and icm. It does have some codes the random multipule cylinder missfire, o2 sensor after the cat, and egr flow insuficent. Next week the cat is going to be replaced with straight pipe and egr deleted, those have been planned for a while. What could cause this ? fpr ?

thanks

Check your fuel pressure, you might be lean. A bad coil tends to misfire on the same 2 cylinders. A bad ICM could cause misfires on all cylinders.

It had a Bosh lifetime warranty fuel pump put in last summer, and new fuel filter last month. How do I check fuel pressure? I dont have a gauge.

You would need to get a fuel pressure gauge.

Okay. Also, I forgot to add that the problems getting worse the longer it goes without fixing and when it does this the trac off light comes on and check engine lights starts blinking.

thanks

The blinking SES light is the misfire, nothing to worry about there. I would suggest taking off the coils and the ICM and clean up any corrosion that might be there. Then use a little dielectric grease when you put it back together.

I did that when I changed the ICM today.

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Inspect your ignition wiring harness for any bad connections or damaged wires.

i did that also when i did the LIM gasket about two weeks ago

thanks

i havent had a chance to get a fuel pressure gauge yet, but would injectors be the promlem ?

thanks