Ok, so ive had this problem for over a month now...trying to self-diagnose and havent been successful. Maybe you guys can offer me some ideas to look for.

I am AWE stage 3 in an '01 S4. Just put the k04s in. Put an MBC in with k03 software to eliminate the taper until i got AWE tuning kit. The problem began at this point. It has perfect vacuum, but wont build boost. If i get on it really hard it builds boost slowly but the needle bounces up and down on the boost gauge, violently.

I pressure tested, bypassed the N249, replaced the DVs, changed the ECU to Awe Stage 3, changed injectors to greenies. Still cant figure out whats causing it. I changed back to stock N75.

I VAGd and found no codes, just an 02 sensor but that came up long after the problem started. I am not getting throttle cut, the only info VAG is giving me is that requested boost is MUCH higher than actual boost.

WHAT COULD IT BE???

TIA

 

Hard to say with no codes? How exactly is vag "telling" you that the requested boost is much higher than it is? Sounds like a boost leak at any rate.

 

Is the requested boost what it should be? On my '01 A4 after installing the K04 software my ECU was only requesting 10 psi when it should have been asking for 20+ psi. I took my car to AWE and they were unable to figure out what was wrong. They tried all kinds of stuff fix it including a new chip with the same software but nothing worked until they installed an older version of the K04 software. Then everything worked fine.

Did you log the maf? Did the g/s look right?

By the way, you might want to post this on the S model forum. They will be more knowledgable about what the appropriate log values should be.

onepoint8tee, logging block 115 with VAG -COM will show requested vs. actual boost.

 

Good to know! Thanks.

 

yea, i logged 115 and the requested boost is perfect...goes all the way to 2460...which is eaxtly what i want to be boosting. actual boost doesnt go over 1600 (logged through 3 gears at WOT)

Havent logged the MAF...dont know what the values should look like.

I did post it in the S line forum, but so far i have gotten more help here. Im just trying to find sum1 whohas had a similar issue and there are more people in this forum.

I dont have any codes. Just an OXYGEN sensor code that popped up the other day (long after the boost issues began) i think the sensor might have gone...

If it were a leak, the pressure test wouldve told me. My intake tract isnt leaking anything whatsoever.(you can here a tiny bubbling in the oil...which is normal)

 

if you log the maf and its running way under what it should but not throwing a maf code... is the maf bad??

 

i wud suppose so...

unless the air reading is accurate and you arent gettingenough air brcause of your intake.

 

Low MAF readings may mean a bad MAF but not always. Check out Baconbait's post about his turbo install problems. We tried 3 different mafs and all were giving the same readings. They can't all be bad. I would think that an S4 with K04s should have some high g/s numbers. If it's under 200 g/s at WOT, I think somethings wrong. Check the 'Zine to see what the MAF numbers should be or call AWE. But, AWE is probably swamped with all the Waterfest stuff this week.

Did you try a throttle body alignment?

Have you checked block 20 to see if the ecu is pulling timing?

Does the air fuel mixture look good? My guess is that if you don't have any boost leaks, something is restricting the air fuel mixture.

This is about the limit of what I can think to check. If none of these turn anything up, you should probably head over to the 'Zine and hit the turbo gurus up for some answers.

 

Yes, ive done a TBA about 3 times. this isnt the problem.

I will check block 20 tonight. If the ECU is pulling timing, what would be the cause of that

I will also check the air/fuel tonight. It may be a bit lean(running a tad hotter) but would this make a difference? What air fuel would cause problems like mine?

Could it be as simple as a dirty air filter? Fuel pump/fuel pump relay???

It feels to me more of an electrical problem.

 

no codes at all??

i know p1137 is bank 1 too lean what would cause it to run lean and be restricted... with a higher flowing exhaust and no boost leaks??

bad maf?