In the past few months, I've replaced the MAF, coils, plugs, DV, vacuum lines, O2 sensors, SAI pump, and valve cover gasket. I still have the following problem: at idle, I have random misfires on every cylinder. When the car goes into limp mode, it seems to "run" fine (but when I clear the codes, idle is very rough and sometimes stalls when doing a cold start). Once accelerating, it feels fine.

This is driving me crazy. I finally went to the mechanic, and he replaced the fuel pump and two breather hoses. The next day and $750 later, the problem has returned. Today I just cleaned the throttle body (which wasn't very dirty), and that hasn't solved it either. What could possibly be left?

 

first, what kind of car/engine do you have? second, have you tried replacing the ignition control modules? its the only thing you don't have listed yet.

 

Have you replaced the fuel filter? And when you "clear" codes are you using a generic code reader or are you using a VAG-COM diagnostic tool?

Which engine and year? If it's a 1.8T it would be worthwhile to perform a boost leak test.

ICM is dependent on year, if he is 2000 or newer (I believe) he wouldn't have an ICM.

 

Sorry for not specifying earlier.

When I took it in last week, the mechanic performed a vacuum test and said it's fine. That's when he noticed the two breather hoses that were cracked (but replacing them didn't make a noticeable difference).

 

Let's hope he's right. But how about the diagnostic tool you have used?

 

Hmm, I didn't think there was an ICM...this is an AWM engine---drive by wire. Unless I'm missing something?

What about the diagnostic tool? I've been using an unregistered version of the Ross Tech software to pull the codes and measurement blocks. If there's something in particular I should look at (for instance, I've checked 003 and can verify that the MAF is working and air seems to be flowing at the right levels), please let me know.

 

You don't have an ICM, each coil has one built-in.

I asked about the diagnostic tool because some people use generic OBDII readers, which have relatively limited functionality on our cars relative to proper diagnostic equipment. You stated that you have cleared some codes, do you recall which they were? And do they come back after being cleared?

 

Last week I cleared a P0411 and the recurring set of P0300-0304 right after I replaced the air pump. The P0300-0304 codes came back, which is why I then took the car to the mechanic because Iw as out of ideas. He replaced the fuel pump. This morning, the P0300-0304 codes came back, as well as P1128 and P1136. I cleared them this evening and then decided to clean out the throttle body. When I put it back in, the P0300-0304 codes came back instantly (though the CEL did not immediately come back).

I have to drive from DC to NJ for a wedding tomorrow, so I'm sure the CEL will come back on during the trip...

 

As expected, all the codes came back. We're back to:

P0300, P0301, P0302, P0304, P1128, and P1136.

Given the other things that I've replaced, this may be:

1) clogged fuel filter
2) clogged catalytic converter

Once the CEL came on, starting it cold is fine (whereas right after clearing the codes, idle is rough and sometimes stalls).

What are the other possibilities?

 

Injectors or fpr maybe?