Ok, I have tired to figure this out but have not had any luck yet. He is getting both a System lean AND a System Rich codes. He was getting just the lean code before then we had it scanned again and it showed up with system lean and a N75 open circuit code. We replaced the N75 valve with a TurboXS MBC and set it at 9PSI (he is not chipped so we kept it at stock settings). After we did that he started getting missfires so he went to get it scanned again to see what cylinders were missfiring but there were no missfire codes, just the system rich and system lean codes. We changed the sparkplugs maybe 2000 miles ago with the proper gapping and everything. I think the system lean and rich codes are because of a bad MAF sensor but I am not sure. And why would the missfire codes not show up? His CEL was flashing everytime you hit the gas peddle hard at all. He is driving a 2001 A4 1.8T with about 117K miles. Any ideas of stuff to try? Oh and we have cleared the codes every time we check them and they keep coming back so I know it's not an old code. He also just replaced his O2 sensor about 5000 miles ago.

Josh

 

could be a sludge problem....if you really like the guy...(not like that!)

put in a new set of plugs for good measure, give him your coilpacks (temporarily)

keep running the MBC, you could even drop the psi to 7 if you wanted

how does it drive exactly, it sounds like some classic missfires, but without codes, i really can't tell you for sure...

sounds like there is some massive missfires that are preventing the gas to be used, which means there is a bunch of unburned fuel leaving the hotside (sounds like the unburned fuel is throwin the codes)

it could also be the ICM...not sure though, start with plugs and cp's

gl!

 

Yeah the problem is I can't use my coilpacks on his engine. I have a late 99 A4 and his is an 01. They use different ones.

Josh

 

try the ECT

 

I think I have a set of coilpacks from a passat that you can have if you need 'em

my money is still on a bad spark...

try changin just the plugs, maybe he could borrow your n75? (instead of runing a mbc(though that shouldn't be the prob.)

hmmmm...doest it hesitate to start? it could simply be a bad sensor?

not posative...weird that it doesn't throw missfire codes

gl

 

The MAF element is toast, its the only thing that can cause a rich and lean concern at the same time. The miss-fires are a possible result from a faulty MAF.