Assuming limp mode but what or why
First post for a long time reader and search button/google guru. I will try and give all information in the first post.
2001.5 S4 tiptronic 171,000 miles on the clock when purchased as a winter project. Picked up cheap like dirt cheap. To the point I was assuming I would be buying turbos however there was no dentist drill sounds, smoke or indications they where shot but 171k and no history.
bone stock with lots of minor issues. No history other than car fax. original owner up to 147k Florida car given to daughter in Michigan Husband actually drove.
Compression on cold engine(during December) is 132-137 should be really good (14.1 x 9.3=131) assume humidity in garage and tester explain higher reading
Vag-com had to many errors to list here but I have gotten it down to Zero.
I replaced the following;
Audi MAF yes I tried a cheap one first Audi rookie mistake
Spider hose assemble Audi
Fuel filter
Air filter
Spark Plugs NGK BKR7E gaped at .028"
Oil change,
Timing belt kit. water pump, tstat, cam seals, tensioner, idlers, crank seal valve cover gaskets the works coolant flush. Remember winter project and no history.
Vacuum lines excluding from waste gate actuators(tested good) and the one coming from N249 where it leaves below the bank 1 fuel rail and ends someplace under the intake manifold. I would like to replace this if I could without removing intake any suggestions?
I am sure I am missing items.
Most all codes where gone except O2, the previous owner had deleted one main cat stated it was plugged. Snow is gone time to test it out I had not driven it since I bought it on Black friday. Time to see what is really going on. Seems to run great compared to before (a ton of misfires) after warming it up time to check turbos. Wow seemed great 10 miles later not so good. I made a couple of runs with Vag-com I was running erratic boost it would be strong for a bit them gone 5 psi not 10.
Installed boost gauge
leak tested. OK
tested n75 it was OK in the end replaced.
Random boost deviation errors negative
quadruple checked for boost leaks at 15 PSI,checked all lines again, MAF hence the OEM.
Finally decided to remove the bank 2 main cat, bank 1 had been done previously. I assumed bank 2 was plugged when doing this I removed the down pipes an made piggy pipes. Checked end play on the turbos .002"on driver side and .0017 on passenger with indicator. Looked over the waste-gates unhooked N75 gates crack open at 7 PSI and are full open at 8 PSI vanes looked great, also noticed that the down pipe nuts where black no signs of rust is this normal or maybe newer turbos? again no history.
Purchased second ECU with stage 2 tune, second O2 delete and imoblizer purchased from local tuner.
Started back up sounds great Zero error codes. Couple of test runs I am very happy. Time to take it for longer run to work and back 25 miles each way. In the morning I am happy 17 psi up to 5800 tapper off to 15 near red line really runs great I think. That night headed home 8 PSI not so good, Vag-Com says replace Lamba sensors(first O2) so I replace both with Bosch not junk ones.
Back to Zero codes still zero codes hours of checking double checking and still Zero codes still have low boost or what seams like limp mode 8 psi. I have driven it about 500 miles this way trying to figure it out.
This is what I have noticed that is associated to when it happens ;
No error codes
G/S seems to be spot on only about 138 when running "limp mode"
Throttle valve position will not go beyond 57%( throttle body adaptation through Vag-com and by battery)
boost request and actual boost are correct ECU is calling for only 8 psi
Seems to happen after it has been running for a time or restarted after engine has been warmed up
When it is running correctly;
G/S runs up to about 250s at max rpm and boost
throttle valve position is 100%
boost request and actual are good.
seems to run great first thing in the morning or when its cold out like today(Michigan still has winter)
My thoughts;
Checked pedal position reads the same if limping or not.
Lamba looks good I see a correction of -3.5 to +4 depending on engine load ect.
It seems like I hear a slight change in exhaust tone when it is running correctly I assume its from the additional boost.
Could be EGT but no error code? most measuring block in the 70s are blank EGT is called out as (bank 1) 940c and (bank 2) 945c never changes. I think they only read from 940~1040c.
random waste gate sticking open(wouldn't this cause a boost devation error)
I know this has been a long post, trying to be specific. I can post logs however block 115 they always match, no errors even when I run the full car through. 3rd gear pulls with and auto don't mean much as kickdown will not allow a full 2000k~6500k run.
Any help is great! If I have missed giving information someone needs I will get it for you.
Thanks for reading a long post!
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Originally Posted by j8x4ngr
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