B6 S4 4.2 Bogging Down at low RPM

[Urban Tank]

First off, Can't thank those of you that have continually helped mme enough!

Full tune up, new coil packs, plugs, rebuilt intake Manifold, actuator working perfect, throttle body lightning fast, fully serviced injectors..... Fully serviced transmission...... This motor WANTS to run hard, idles perfect, 2 seconds from initial cold start of light chain rattle at start......... she sounds incredibly healthy........ plenty of power...... RUNS GREAT, just dumping fuel on the passenger bank.....


PROBLEM is she is bogging down at low RPM, say below 3000 RPM. She is running incredibly rich Air Fuel Ratio is mirrored -.8 and +1.6. Passenger side bank is running incredibly rich , drivers bank is compensating......

Dreaded P340 and P345 both calling for cam curcuit A on both sides..........Wiring, sensor, or much worse ?

[Urban Tank]

@Zolli please Un FUCH Me :). Its so hard for me to beleive this motor is out of time........Ive fought to unmolest more molestations than Ive ever seen in a nice car. Its so much harder to unmolest all these little things having not been the one to take her apart or see her correct initially. Some idiot had the Bank 1 Cam sensor and bank 2 Sensor swapped. They had so much tension on the harness forcing that 90° bank2 sensor in bank 1 im hoping an issue in the wiring there might explain my bank 1 rich fuel dumping bog until she gets some revolutions and takes off like a rocket.......After testing each with multi meter and a magnet 1 was bad. My fat knuckles are trying their best to fight through it and get this bad girl driveable!

Shes flawless from 30mph and beyond........ but a Pontiac Aztec could smoke me off the line.......... The Hydraulic tensioner on bank 1 passenger side looks new. Far less chain rattle even at 0° Fahrenheit than the few other V8s I've owned. She doesnt leak anything thanx to hours of swearing and gasket and oring replacement. Ive treated her to all genuine parts.......Somebody tell me straight, is it pull the motor time? Failed cam phaser? Any tricks for testing the cam position sensor connector to the pcm?

[Zolli]

Hm I think I might be out of my depth here, especially over the internetz, but I can toss out my spitball ideas.

Yes, could be wires. Electrical gremlins are the worst.

Clean the MAF? Air filter?

Throttle position sensor?

Failing O2 sensor that for some reason isn’t throwing a code?

Clogged cat on one side that also isn’t throwing a code?

It’s hard, since higher rpms apparently smooth it out, and the air-fuel mixture isn’t evenly wonky.

Maybe one of the fuel rails has something wrong? Idk

It’s an automatic transmission, and you’re sure it’s good?

The cam codes could indeed be the culprit.

Sorry I can’t help more. We need real big brains on this one!

[Urban Tank]

If I didn't have a shop (warehouse I use service my own to service my own fleet of classics and heavy equipment, a couple hundred k in Snap-On and Mac at the ready, and the affinity for the sheer punishment this beauty has already put me through, coupled with the sheer obsession with not letting this S4 beat me, id hunt down an Indy but Im now pot committed:).

There is NOTHING more frustrating than finding things wrong, remedying them, and only making the car operate worse :).

Id like to think anyone who's ever wrenched on a troublesome Audi will have a sense of humor........So Ill send anyone who can steer me in the right direction to their favorite local Korean BBQ or Rub N Tug on my dime........

Im setting aside the 67 SS Convertible and 69 Grandprix 428 HO to play with this Ugly Girl at the dance because Ive been good to her and its time for her to make Daddy Happy!

[Urban Tank]

Hm I think I might be out of my depth here, especially over the internetz, but I can toss out my spitball ideas.

Yes, could be wires. Electrical gremlins are the worst.

Clean the MAF? Air filter?

Throttle position sensor?

Failing O2 sensor that for some reason isn’t throwing a code?

Clogged cat on one side that also isn’t throwing a code?

It’s hard, since higher rpms apparently smooth it out, and the air-fuel mixture isn’t evenly wonky.

Maybe one of the fuel rails has something wrong? Idk

It’s an automatic transmission, and you’re sure it’s good?

The cam codes could indeed be the culprit.

Sorry I can’t help more. We need real big brains on this one!

Never thought to check the TPS but I verified the Throttle Body response visually to which the flap is lighting fast and well in sync with the pedal but the engine response is delayed until high rpm. I can have the Throttle to the floor but she doest care at low rpm. The second i downshift she has endless and instant response.

My father rebuilt transmissions for 50 years so I was spoiled there and didn't learn as much as I should have :).. I did fully service the trans, filter, fluid. Pan and magnets were far better than expected.

I replaced and installed the correct cam position sensors which only seemed to make it run worse. Before it had 1 bad sensor and both were installed on the wrong side go figure. I don't have vag but do have Snapon and Altel and can pull anything those wiser might need to make me feel more mentally challenged than I already do........ But I refuse to give up!

[Urban Tank]

To me the transmission looked extremely clean although it was evident that it has been changed. I used Royal Purple as I was told it was fine and it was the highest quality available locally.
You might be onto something with a clogged cat or even the injectors which I also just serviced. Scan tool had the temps in sync but when I attempted to shoot the pipe welds just before the cats to measure temp from one side to the other , i was getting a barrage of temps but the bank 1 cat (passenger side ) exhaust pipe was roughly 50° cooler and didn't seem to seemed to be burning up as well

[Urban Tank]

Two codes.....17755 &17748 both calling for Sensor Incorrect allocation

[Zolli]

Two codes.....17755 &17748 both calling for Sensor Incorrect allocation

Probably bad news. Ross-Tech says that when these two codes are displayed simultaneously, particularly after revving the engine above 1800rpms, it is likely that the tensioners were installed on the wrong heads (passenger tensioner on the driver side, and vice versa).

http://wiki.ross-tech.com/wiki/index...8/P1340/004928

I don’t know if it would make a difference, but that might be why the sensors were on opposite sides.

Ugh

[Urban Tank]

See it made no sense to me that the CPS with the right angle turn was on the bank 1 passenger side because it made the wires so taunt. So I swapped them and it ran worse...... The bank 1 passenger side clearly had the hydraulic tesioner changed.......I guess I should have taken this as a bad sign as who does one side and not the other........I bought this car as it seemed clean with low miles.........

Im now guessing the incorrect radiator, these other molestations were likely a bad inbetween owner trying to get her back on the road ........ The car has a few blemishes but im guessing was a nice car and one McGyver was all it took........

Fook me........ so much time........Im strongly contemplating parting my A6 C6 4 2 and this S4B6 out as Im going to take a bath either way and getting myself a standard as its what I really wanted.........Once removed and on the stand it will be easy to fix both and it will be easy for me to document both running and with low milage.........Im not wanting to give up but now that Im hooked I guess I'd rather put the time into what I want.

[Urban Tank]

Probably bad news. Ross-Tech says that when these two codes are displayed simultaneously, particularly after revving the engine above 1800rpms, it is likely that the tensioners were installed on the wrong heads (passenger tensioner on the driver side, and vice versa).

http://wiki.ross-tech.com/wiki/index...8/P1340/004928

I don’t know if it would make a difference, but that might be why the sensors were on opposite sides.

Ugh

What sux about this is I knew I was fighting something stupid....... There were so many signs with this car that it had been babied and well cared for.........and then there were some like the radiator, a few broken connectors , and this boneheadedness that someone clearly was in over their head....... This car was well cared for for 98% of its miles as I knew it was healthy ...........Zero wear Recaro's, clean body, all genuine parts , the history i do have........It only takes one bad mechanic or owner to turn regular maintenance into a nightmare. Shame on me for not being more dilligent in diagnosis.....

[Zolli]

Arg, I think you’re right about an “in-between” owner that’s messed all this up.

I’m sorry, man.

However, if you end up wanting to pull the engine, you probably can handle that more easily than you might think.

[Urban Tank]

It makes sense.......As I myself botched that bank 1 was the passenger side.......Wrong radiator, wrong hydraulic tensioner.....Rookie mistake on my part not being more dilligent withmore dilligent with diagnosis. Who would have thought someone installed the wrong tensioner on the wrong bank when there were other more obvious ATF mixture issues like the broken intake manifold flap. And I likely could pull the trans and drop it down enough to change but might as well pull the engine. And then its full timing kit , two new tensioners......and then its manual swap or recoup what I can and buy what I want........
B7 sounds like a nice upgrade?