RhinoJohn

First post as a member, want to thank everyone who contributes to this forum as in almost every case i've found the needed help from posts.

Son, 16, almost 17 dealing with cancer, that's why I got this Allroad, for him. he was interested in Audi as i also purchased a 2005 A6 a few years ago. Its been a great distraction for him and he's become an enthusiast. I had the benefit of a perfectionist Auto shop teacher in HS, and he taught us how to troubleshoot. Plymouth Troubleshooting contest esq. I appreciate all he did for me, use these skills everyday. My son and i have invested some hours on this beast and he's learned a lot and takes great care of it.

a week ago we parked it as it had the flashing CEL. idle was rough, so he pulled the codes,
P1557 – Charge Pressure Control: Positive Deviation
P1131 – Oxygen (Lambda) Sensor: B2 S1: Internal Resistance Too High
P0431 – Warm Up Catalyst: Bank 2: Efficiency Below Threshold
P0300 – Random/Multiple Cylinder Misfire Detected
P0304 – Cylinder 4 Misfire Detected

Pulled IC #5 swapped with #4, codes followed coil in #5. went away in #4. Purchased one new coil, left former #5 in #4 and put new coil in #5.
CEL off.
Drove a 2 miles - VAG com, codes - all clear. Few days later, rough idle, p0300 and P0304 and P1557 again, but no 1131 and no P0431. Thinking a bad injector, or maybe a bad #4 plug? Could use some ideas and recommendations. Plugs <1 year old.
No picnic if intake R&R, but if i have to, i'll replace everything i can while its off, all injectors, all gaskets and any other items. I have until Saturday night to resolve, hope to have it running great before i leave.

Thanks in advance.

PaperToast

id bet the ICM's are wigging out.
swap those and see if the misfires switches sides

LakeTahoeQuattro

When you replace ONE icm in a batch of 5 other old ones, it sometimes causes the next weakest icm to go bad.

On a friends allroad with 165K I had to replace two injectors on #4 and #5 and had to change the ICM on #3 and #2 to rid his misfires that all of a sudden poped up when we went stg1 on his car.

Keep working on it, you will eventually fix the misfires. Also replace all the plugs.

In Re to your p1557, I will tell you its a boost leak. There will be other people here that say it is your turbos boosting too much, but the three times I have had the p1557 it was a boost leak. First time was a ripped Throttle body boot, second time was loose fuel rail (loose injector) and third time was loose hose on IC output.

Your 02 sensors mean you need to code em out or or replace the sensors

RhinoJohn

Thanks for the responses. I'll check the other ICMs and i've heard they can go bad in groups as you stated, they are all the same vintage.
And what you said about the p1557 makes a lot of sense. found one loose clamp on the throttle body connector and one of the clips, my son thought was broken, but it wasn't.

RhinoJohn

New plugs all around NGK, gapped, ICM #4 new, ICM #5 new.
confirmed all hoses and connections from MAF and air flow are tightly sealed, no noticeable leaks.
P1557 code gone.
But...
Still rough idle, throws P0300 random misfire and P0304 cylinder 4 misfire.
ruled out plugs and ICM.
injector? Is there a way to replace an injector w/o pulling the intake manifold? If i pull it, I'll replace all 6 injectors, what else should i take care of while the intake is off? will that make getting at the O2 sensors pre-cat easier?
thanks again for the help. This #4 misfire is consistent.

PaperToast

what octane gas do you run?
if its less than 91, might wanna go gas up with some top tier 91, 93 if available (shell, chevron, conoco, ect) and run a can of 44k.
id try that before pulling the intake mani

RhinoJohn

91 is the highest we have - used some Lucas injector and Octane boost, - i swapped ICMs and misfire now shows on Cyl #1.
should have tried that first.
heading to parts store.
i pulled the old plugs, they were gapped .40+, but may be okay for Denso, new NGKs at .32.
report back when new ICMs in place.

RhinoJohn

new ICM-Ignition Control Modules, no more misfire, still pulling p1557.
rechecked and all hoses, connections are tight, no leaks detected, still in limp mode.

LakeTahoeQuattro

Just do a boost leak test. Youll never find the leak with a visual inspection. Buy the boost leak tester, it is like $30, youll use it many many times in your audi ownership life of this engine

Audi S4 2.7T - TURBO BOOST LEAK TESTERS

I know awe makes one too

RhinoJohn

replaced both ICMs, replaced the throttle body boot and no more codes.
Allroad registered and that familiar turbo noise and power are back.
Thanks for the help.