Phil type 951

I was at Grattan raceway this weekend and got low on fuel during the last session. Well the last lap was my best time yet of a low 1:38 so I wanted to get another lap or 2 in before the end of the day. About a minute later I experienced some fuel splash in the tank and the engine stumbled for a fraction of a second. I know this was dumb to let happen but I let it happen anyway.

I got gas and everything seemed ok but now I'm only getting about 10psi max boost. What happened to the car when it ran out of fuel and how do I get my power back? I have a Vag but haven't used it yet. I also have APR EMCS and did the throttle body adaptation. Should I pull my ECU to erase anything EMCS didn't?

In addition to this new issue I've had another l boost issue (12psi peak before "race" n75 installed 16psi after install) for several months and I haven't been able to figure anything out. I think it's a small boost leak but haven't removed all the hoses to visually inspect them. I've looked @ all the basics but don't know what I should do. This is what I've done.

I had the dealership do a vacuum test
Replaced the o2 sensors (they weren't totally dead but were old and not showing good #)
Replaced fuel filter
Replaced intercooler due to a few small holes
Replaced all the small vacuum lines from BBV to intake
BBV replaced w/ tt valve
Stock n75 frequency valve replaced then returned due to no change in performance.

Car is a 1998 a4 1.8t with 63K on the clock
The only engine mods are the APR chip, a 3" test pipe, apr exhaust, a 200quattro n75 "race valve"

Before I ran out of gas I was thinking the MAF was going bad but I don't know how to really test it. I was told that if you unplug the MAF the ecu will run the car from a preset safe map. When I did this the car was even slower with only about 3psi. Does this trick only work on DBW cars?

What do you guys think is going on here? Do you think my MAF is bad or I have a small leak?

Most importantly how do I get my already low boost back to the pre fuel splash level of 16psi??

Thanks for the help guys! any ideas would be great! -phil

Audi2ptzero

Then do a throttle adapt with the vag and see if that does it. I used to run my car till it ran out of gas going to the track, I would then just replace my chip and never saw a boost issue.

xr4tic

you can also try clearing the adaptation values.

The best test for the MAF would be to datalog MAF vs. RPM on a WOT run.

Clear the codes, reset the adaptation values, run a TB alignment, and then datalog block 2 and block 31.

That will show you MAF, injector time, RPM, and O2 voltage. you can send me the logs afterwards, and I can check them out.

I think with the MAF unplugged, it disables the frequency valve, which is probably why you only saw 3 psi.

mau

When you clear the codes, doesn't it reset everything on the ECU?


Mau

xr4tic

I figure I might as well do it while I'm in there. I probably should find out what it does <ul><li><a href="http://www.ross-tech.com/vag-com/tour/adaptation_screen.html">http://www.ross-tech.com/vag-com/tour/adaptation_screen.html</a></li></ul>