Boost on my 99 audi a4 quattro 1.8t

[Flufffylunchbox]

I just replaced the ko3 turbo and redid some vacuum lines and it wont go past 5 on the boost gauge brown n75

[Seerlah]

Not understanding what you mean by brown n75? Different version n75 than stock?

But stock boost on the AEB is 7psi. 5psi is limp mode, which is usually caused by a lean issue.

[Flufffylunchbox]

Ok what could be causing lean issue it run rich on the air fuel ratio gauge

[Seerlah]

Could be a dirty/faulty MAF. When your MAF goes bad, the ECM goes into limp mods and goes in a rich fueling default to protect the engine. If you have VCDS, log your MAF. Or if never replaced, they are recommended to be replaced at 100k.

Not saying throw parts at the car to fix it, but this is a common thing. You can try CRC MAF cleaner, but you won't really know for sure if your MAF is the issue unless you log it.

[Flufffylunchbox]

I have a scan tool that I can watch live data on

[Seerlah]

Log your MAF readings, doing a 3rd gear WOT (wide open throttle aka floor it) highway pull or long stretch of road (watch for the cops when doing this). You should be close to 120 g/s. You read MAF readings by grams per second. The g/s reading should be 80% of your bhp/chp.

[Flufffylunchbox]

Ok

[Flufffylunchbox]

So on the maf sensor us reading ever where at idle it drop to 1.89 then highest is 104.

[Seerlah]

Replace your MAF. Only replace with a Bosch unit, that is oem (bosch os oem without the vw/audi logos on them).

But before you do this, you should have done a boost leak test to confirm any leaks (I assumed you did this already). This will also cause a lean condition, causing you to go into limp mode and run low MAF readings.

[velizjose24]

I have a Bosch unit just sitting around, if interested let me know, I had purchased one a while back and put it up as a spare part.


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[velizjose24]

Replace your MAF. Only replace with a Bosch unit, that is oem (bosch os oem without the vw/audi logos on them).

But before you do this, you should have done a boost leak test to confirm any leaks (I assumed you did this already). This will also cause a lean condition, causing you to go into limp mode and run low MAF readings.

I have a aftermarket maf in my car and it’s been fine for 2 years now so it doesn’t have to be Bosch specifically , not trying to knock what you said but just my experience.


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[Seerlah]

Bosch MAF lasts roughly 100k. Can't say the same for other brands. I picked up a crank position sensor from Advanced Auto before when in a crunch. Lasted a few months before leaving me stranded. Learned from that point to stick with Bosch, which is OEM.

There are of course other good brands like Hitachi, but I like to suggest OEM over anything. People just don't know Bosch is the OE supplier for many stock components, including your ECU.

[Flufffylunchbox]

How much velizhose24

[velizjose24]

How much velizhose24

Pm’ed


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