Rowdy-audi

Hey, i got a 2000 Audi s4, with about 120,000kms, its got a Apr chip and catback and an upgraded diverter valve. Yesterday I installed a AWE boost gauge. Very thing went smooth on the install. Took it for a test drive and it boost perfectly fine topping out at about 10 to 12 psi and a solid 18 to 20 in.Hg vac pressure at ilde.
Today i was driving it and it boosted to 10psi, then shot up to 15 then dropped. when it did this the check engine light started turning on and off. When i stopped my vac pressure was at 10 in.Hg. That continued for a little while. IT was alright later today but it still spikes every so often when i go full throttle any ideas?

Thanks

Jeff

rktskicar

check your car for codes and boost leaks. Check boost gauge against VAG. May have leak from boost gauge install.

Bruce

Rowdy-audi

If my vac pressure is back to around 20in.Hg at ilde wouldnt that eliminate the chance of a leak somewhere in the boost line?

rktskicar

vac is vac and boost is boost. Not necessarily the same, Post up some logs. Block 115 VAG, 3rd gear, 3K to redline.

Bruce

Indyxtype

2nd on boost leak. If you can't track it down by poking around, you can always get the awe pressure tester.

Rowdy-audi

The car has be performing fine ever since. It kinda strange though when i pull in 3rd it only boosts at about 12 psi, but when i pull in 6th it boosts right to 15?

I dont have a engine diagnostic so i cant give super accurate figures.

I'm goin go around and make sure all the zip ties are tight and all the hoses are good then take er for a for a cruise and try and solve the problem i only had a chance to try and open it up on my way to work so it was a little hard in alot of traffic haha

rktskicar

You will need to run some logs to find the reason for this. VAG blocks 3 and 115 during 3 rd gear WOT run from about 3K to redline. Hopefully you have a VAG (or ECUx).

Bruce

RolledMySTi

Could be your N75

bnr32_coupe

have you considered a boost leak test?