hey everyone! little introduction here before I start:
Audi S5 2009 with the 4.2
139 000 km (86k miles)
couple mods on it ; mostly esthetical (rs5 style bumper, cf diffuser, mirrors)
Mods on engine/performance : JHM TEST PIPES, Magnaflow rear mufflers and tail pipes.
before i got the car, it had around 120k km (so about 74k miles); previous owner gave me about 14 000 CAD$ of receipts of recent stuff that was done, notably Carbon cleaning, clutch replacement, flywheel replacement, bunch of stuff for the powersteering and rack, both HPFPS, carbon cleaning, 4 knock sensors, a passanger motor mount.
The car ran beautifully, but the transmission had a 3rd gear grind so i had a good deal on it. He also had apparently broken the brand new clutch.
So i had many misfortunes during transmission replacement, putting 2 new ones in and a new clutch and both used transmissions i had installed ended up being bad with grinding gears.
long story short, last time transmission was out, they did indeed fix it, and i had them replace the cats with JHM test pipes. they said they had to replace some o2 sensors because they were pretty seized up and got messed up during removal.
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all of this leads to now. when i dropped the car off, engine ran pêrfect. When i got the car back, transmission ran beautifully, and so did the car, up until about 20 minutes later when it got hot. it started misfiring badly and hesitating and smoke was coming out of driver side (bank2) tailpipe. to the point I had to get it towed.
So i towed it to a reputable shop local to me of audi specialists, the codes I had were misfires on mostly bank 2 , and it apparantly had bad o2 sensor voltages. I suspected that it had something to do with o2 or leaks as the car had always ran beautifully since i had it and replacing the transmission and test pipes, i figured it was something to do with newly installed test pipes.
So the shop eventually came back to me with a diagnostic : they had to replace both o2 sensors (that were already replaced) and told me driver motor mount was broken but it wasnt URGENT to change, and needed to change the thermostat. I also had unrelated codes with dynamic steering, that they didnt further diagnose than the fact that i had some water infiltration on driver side foot.
Indeed, i fixed the driver side leak, that was coming from under the windshield, the gaskets werent propperly reseated and water was entering under the carpet and broke the dynamic steering ECU (i fixed this now with a new module).
so they changed out thermostat, and while at it they broke the water pump shaft, so had to replace whole water pump rather than just thermostat... i wasn't too happy about that.
and they went ahead and changed out both front bank1 and 2 o2s and told me it was fixed.
Unfortuately, it came back.
When i start the car, it runs beautifully, up until sometimes, usually when it's hot (temp at least middle of the guage, VCDS reports about 95-100 celcius) then the voltages on my bank 2 sensor shoot up and fuel trims go to maximum +25-27 (idling, or driving) and it starts running rough/ misfiring. mostly on bank 2
A few times, not often, bank 1 has also leaned up and added fuel, but this has only happened once or twice.
If i run the car and dont let it idle too long, i can drive without problems for a while, problem generally shows up when it idles for a while. when the problem appears, clearing ecu codes generally makes it run better momentarily.
When unplugging the o2 sensor on bank2, car seams to run fine, but i havent tested this TOO much as it scares me to run the car in open loop.
I thought of maybe some air entering Before the b2s1 causing wrong reading, but i can sometimes idle 10-15 minutes with fine voltage to it, then randomly it goes up to about 2.7 to 3v and stays there even when adding maximum fuel +25.
What i have done to try and fix this since :
8 new injectors with o rings and metal hardware
8 new spark plugs
8 new coils
carbon cleaning
new PCV
new intake manifold gaskets
cleaned up TB, air filter
check for leaks (haven't smoke tested though, but i did spray intake cleaner around to try and find some leaks.
cleaned MAF
probably some other stuff too
compression test showed around 200-210 psi on all cylinders (engine slightly warmed, no oil)
tried plugging in my new 034 mount solenoid to left side to eliminate the motor mount being the issue
Possibilities:
N80 valve?
combi valve?
Other random valves?
timing? vdcs reports the 93 block at like -1 and -2 so i think they arent stretched. cam adjustments b1 exhaust are -20 and -20.5 and cam adjustment intake b1 22 and b2 21.5 and i cant find cam adjustment bank 2 exhaust i think (would need to recheck)
fuel rail pressure at idle is 25.73 bar and giving throttle at idle i think goes to 57 bar or so im not sure i've measured all the correct blocks.
i don't think the problem is with fuel as both HPFPS are new from 20k km and all injectors brand new with hitachis
ecu problem?
If i drive it around i eventually get the code of bank 2 lean off idle (but it goes lean on idle too)
I'm stumped and dont know what to do now , any help is welcome! i've read EVERY thread, EVERYWHERE and still unsure what the issue may be. If it was exhaust leak before sensor (i think i may have a very tiny one at the flange from manifold to JHM pipe, but if that were the problem, why does it only show up when car gets really hot?
oh VERY IMPORTANT almost forgot : when i replaced the plugs, they were really carbon fouled, showing its probably actually just running super rich from the lean readings of the b2s1, but im not entirely sure. New plugs also seam to have fouled with carbon super rapidly.
Since replacing injectors and carbon cleaning, car seams to misfire less, but it still goes to 2.8v on the bank 2 lambda sensor, so it still dumps max fuel into that bank, hence causing bunch of problems.
I don'T know what to monitor in VCDS to get more info, what to check when theres no problem with it, what to check when voltage spikes up, etc.
right now i'm in the process of trying to remove the test pipe and replace the gasket manifold to test pipe, but its a huge PITA and i'd honestly rather not take the pipe off as the access is horrible, and the seamingly very tiny leak is inaudible, im not even sure there is one, i sprayed some soapy water up there as much as i could while pressurising the exhaust with reversed out shop vac and saw tiny bubbles but it was very slight, i doubt its an issue and fail to understand why it would only cause an issue randomly like this.
sorry for the long read, i'm trying to be as detailed as possible to not miss anything, any leads are welcome here! thanks
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