[paraplan]

Originally Posted by Scrippy

O2's control air fuel bro. Well not directly but malfunctioning O2's will affect it. Cats? Exhaust status?

So do you suggest replacing O2 sensors? I believe there are two of them (each $200). Is there any way to diagnose them with BT before replacing?
Catalytic converters I believe worth even more ((
I'd go that route, but want to make sure those parts are really faulty.

[Dmacc]

Originally Posted by parapln

Having the same saga with going after rough idle fix. This is what was done so far:
1) replaced spark plugs
2) walnut shell blasting of intake valves
3) replaced all 6 coils
4) replaced battery
5) replaced all 6 injectors (some appeared to be leaky)
6) replaced leaky valve cover gasket
7) replaced 6 fuel rails (going after fuel smell, propably the real cause was a leaky injector and not rails)
8) cleaned MAP and TMAP sensors
9) HPFP was replaced aroung 45K (now the car has 91k)

Rough idle is still there, however I do see some significant improvement in the way engine sounds now. However jerkiness is still there, no codes or warning lights. I'm not sure what to do at this point. Some people suggest replacing throttle block, but now it feels like trying to move in the dark just wasting $. I have BT and INPA cables and wonder if some parameter diagnostics could be used to find the root cause.
Does anyone have any idea which direction to move at this point?

Could you describe this rough idle with a little more detail? When you are idling with the AC off, does your idle bounce from 600-800rpm back and forth? Is the jerkiness you're experiencing in the lower RPMs as you are taking off from a stop?

[paraplan]

Originally Posted by Dmacc

Could you describe this rough idle with a little more detail? When you are idling with the AC off, does your idle bounce from 600-800rpm back and forth? Is the jerkiness you're experiencing in the lower RPMs as you are taking off from a stop?

Yes, Rpms fluctuate between 620-750 every 15-20 seconds. When it happens the engine shakes and it can be felt through shifter or steering wheel. Passenger can notice it too. When the car runs at higher rpms this does not happen.

[924er]

Originally Posted by parapln

Yes, Rpms fluctuate between 620-750 every 15-20 seconds. When it happens the engine shakes and it can be felt through shifter or steering wheel. Passenger can notice it too. When the car runs at higher rpms this does not happen.

Any codes? My car was doing that until I got it checked out by the dealer. Cyl 5 was misfiring due to bad coil. Although Cobb ap showed no codes. Bt pulls more specific codes

[Dmacc]

Originally Posted by parapln

Yes, Rpms fluctuate between 620-750 every 15-20 seconds. When it happens the engine shakes and it can be felt through shifter or steering wheel. Passenger can notice it too. When the car runs at higher rpms this does not happen.

I would replace your vacuum lines if they're pretty old, and maybe check your chargepipe and intercooler connections for a boost leak. My car was running just like this until I replaced all vac lines, fixed my boost leak, and even replacing the old boost solenoids fixed my vacuum. I then reset all adaptations with my OpenFlash Tablet including a DME reset and my throttle was back to being crisp with minimal wg rattle. Hope this helps out.

[deltalima0]

Originally Posted by parapln

Yes, Rpms fluctuate between 620-750 every 15-20 seconds. When it happens the engine shakes and it can be felt through shifter or steering wheel. Passenger can notice it too. When the car runs at higher rpms this does not happen.

I had exactly what you are describing I could feel it in my butt as the car just felt off a bit. The stumble was every 15-20 seconds. I replaced all 6 injectors and it fixed the problem. #1 injector was totally trashed completely blackened and the rubber piece on the tip was completely gone.

I know you have replaced the injectors already, but prior to replacing injectors i replaced the vanos solenoids and it smoothed some things out. It was strange also how at 4000 rpm or above the car did not feel weird and ran well when in that rpm range, but below that it spooled slow and felt like crap.

[paraplan]

Originally Posted by 924er

Any codes? My car was doing that until I got it checked out by the dealer. Cyl 5 was misfiring due to bad coil. Although Cobb ap showed no codes. Bt pulls more specific codes

BT does not show any codes whatsoever.

[paraplan]

Originally Posted by Dmacc

I would replace your vacuum lines if they're pretty old, and maybe check your chargepipe and intercooler connections for a boost leak. My car was running just like this until I replaced all vac lines, fixed my boost leak, and even replacing the old boost solenoids fixed my vacuum. I then reset all adaptations with my OpenFlash Tablet including a DME reset and my throttle was back to being crisp with minimal wg rattle. Hope this helps out.

Yes, I forgot to mention that ALL vacuum lines were changed. Adaptations were reset when I was replacing valve cover gasket as I disconnected battery for a week or so. However I do not beleive in adaptation theory, I also explicitly reset them later with BT.
How do I check the charge pipe and intercooler connections for a leak? I heard about smoke tests but not sure how to do it.

[E92ML]

Walnut blasting fixed my rough idle problems

[paraplan]

Originally Posted by E92ML

Walnut blasting fixed my rough idle problems

Wish it was that easy in my case This was one of the things I tried first before doing any of the expensive replacements.

[deltalima0]

Originally Posted by parapln

Wish it was that easy in my case This was one of the things I tried first before doing any of the expensive replacements.

Yeah same I never got any codes so it was somewhat trial and error I went with new plugs first then new O2 sensors, vans solenoids and finally injectors.

[924er]

Originally Posted by deltalima0

Yeah same I never got any codes so it was somewhat trial and error I went with new plugs first then new O2 sensors, vans solenoids and finally injectors.

You should try walnut blasting. Carbon buildup won't throw codes. It's good for the car anyways so it's not really a waste of money. How many miles are you at?

[paraplan]

Originally Posted by deltalima0

Yeah same I never got any codes so it was somewhat trial and error I went with new plugs first then new O2 sensors, vans solenoids and finally injectors.

Vanos solenoids together with Vanos itself were replaced on this car about 40K ago... That was a whole other issue, but the car was still under warranty during that time.

[paraplan]

Originally Posted by 924er

You should try walnut blasting. Carbon buildup won't throw codes. It's good for the car anyways so it's not really a waste of money. How many miles are you at?

I'm @ 91k now. If you get a few posts higher, you will see the list of things that I've done already, walnut shell blasting was the first thing I tried. This is how my intake valves look like:

[924er]

Originally Posted by parapln

I'm @ 91k now. If you get a few posts higher, you will see the list of things that I've done already, walnut shell blasting was the first thing I tried. This is how my intake valves look like:

CLEAN!!!

so what haven't you changed? low pressure fuel sensor? HPFP?

[paraplan]

Originally Posted by 924er

CLEAN!!!

so what haven't you changed? low pressure fuel sensor? HPFP?

HPFP was replaced by a dealer a few years ago. And yes, I have not yet tried replacing the sensor.
One thing I really want to try is smoke test of intake vacuum, but i don't have a smoke machine. Commercial smoke machines are ridiculously expensive for some reason, so I'm looking into building one myself...

[theweebabySeamus]

Add me to the list. Not to bump an old thread, but has anybody ever compared what types of plugs used?

I pulled my old (worn out, but uniformly worn out) Bosch plugs at 91k. Ran some NGKs hastily gapped to .022 and it stuttered a little while driving it cold. Pulled them and regapped carefully to .022, same issue. Gapped them to roughly .027, a loose wire gauge .025 but not quite .028. Cold driving was a little better but I decided to try some Boschs instead.

I installed the Bosch today and it ran great the first time, I started getting the idle issue the second time I drove it. I tried resetting the adaptations via my jb4 and it hasn't started helping yet.

[Digitalism]

Can the Bosch plugs be gapped?

Thought it was the NGK plugs which were being gapped.

[theweebabySeamus]

You probably could gap the Boschs, but they're supposed to come pregapped.

**editted my first post, realized it made no sense.**

[litxus]

Originally Posted by parapln

HPFP was replaced by a dealer a few years ago. And yes, I have not yet tried replacing the sensor.
One thing I really want to try is smoke test of intake vacuum, but i don't have a smoke machine. Commercial smoke machines are ridiculously expensive for some reason, so I'm looking into building one myself...

I did not see that you replaced injectors? They usually start to go around 100k or so. My idle was not too bad when cold, but driving made it choppy. After car warmed up it would run fine. Now with new injectors I still have a stumbling rpm between around 2-4k rarely at times on WOT. I'm waiting for MHD tuner to come out so I can get that, log and find out what is really going on, besides replacing coils, plugs, vacuum lines, injectors. I'm guessing either HPFP or LPFP at this point as most everything was replaced and yeah, just found my valve cover gasket have a very small leak.

[AWD Addict]

Originally Posted by parapln

Does anyone have any idea which direction to move at this point?

Quit.

I've tried it all. I'm convinced it's something that my car will always have. Stick to name brand gas, and keep your plugs fresh, and you'll minimize it to the highest extent.

[DetectiveLoki]

I've been having this problem for months now. A year ago I had issues with rough idle when it was cold (changed plugs and it fixed that). Half a year later I get rough idle when I turn on my car with an engine that is already warmed up (No rough idle at cold start.) If I don't give it a minute and drive off, my car engine would completely shut off. I can drive off totally fine when engine is at cold start up.

Anybody have similar issues with mine?