So I have a customers 05 2.5 turbo that has been having issues for awhile. It came in with a multiple cylinder missfire, cylinder 4 missfire, flashing CEL and cruise and irradic idle.

We cleared the codes, cleaned the throttle body and the #4 coil pack ( we had a good one used one to use for a test).

This seemed to make the situation better for a couple weeks but it all came back. 

Does anyone have any suggestions or seen this before?

Thanks

 

How many miles? How old are the plugs? What kind are they?

Have you checked compression? Valve lash? Timing?

Edited November 15, 201312 yr by Fairtax4me

it has 107,105. I think we put new plugs in it last spring... I know we at least replaced #4s plug when we did the coil pack.

The plugs would have been whatever the computer called for. NGK. 

Havent check compression yet or valve lash.

At idle the timng is at 19 deg.

The issues seem to be mainly at idle and it smooths out at upper rmps. 

Definitely check compression. We had an issue like that in a 96 that turned out to be a dropped valve guide.

 

 

Is it worse when warm?

 

Ignition timing is irrelevant since you can't set it. Incorrect Cam timing is a bajillion times more likely to be a problem than ignition timing on a modern car.

Check compression for sure. Being a turbo and the #4 missing it could have broken ringlands. 

Ok finally got the car in again to check the engine/compression. This is what i have:

1 and 3 are 127

4 is 0

2 is 75

Ok heres the issue... car idles like crap... obviously because its runningn on 2 cylinder and not even very well on two.

When you step on the gas the car has a little hesititation but then runs totally smoothly and seems to have tons of power.

Does this still see like rings?

I also checked the timing belt and all 4 cams were on their marks.  I didn't have time to take the pulley off and check that so its possible the crank timing could be off.  When this is the case i usually see a cam position sensor code.

Any thoughts????

thanks

Not very often you end up with burned valves on 2 cylinders at the same time, but that's pretty likely the issue here.

 

Check valve lash clearance.

It could be broken ring lands on the low cylinders.

 

One other thing to check is the AVCS banjo bolt screens. Also check the turbo oil feed banjo bolt.