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View Full Version : Bad MAF? Vacuum Leak? WTF? yeah Help please!



md_medic
10-27-2014, 01:53 PM
I have a 99 A4 1.8t. I have a stage II Speed Tuning chip,Upgrade'd inlet hose, front mounted intercooler. 3" test pipe and exhaust, factory airbox with smoothed out insides and a hole (doubly covered with screen) on the bottom (Oh yeah K&7 panel filter). I noticed the car would buck /surge under load. For example if I am going up and Incline the car really starts to buck/surge right before it downshifts. The car has always really seemed underpowered bu that is for another day. Today I was going up a similar incline as It started to do the same routine however this time if I let off the gas it was a rough idle almost as if I was outta gas. When I reached a turn off area at the top of the hill I popped the hood and nothing struck me out of the ordinary. I ran a VAG scan on it and got the following results:
3 Faults Found:
17963 - Charge Pressure
P1555 - 35-10 - Maximum Limit Exceeded - Intermittent
16486 - Mass Air Flow Sensor (G70)
P0102 - 35-00 - Signal too Low
17953 - Throttle Valve Controller
P1545 - 35-10 - Malfunction - Intermittent
Readiness: 0000 0100
Just in the process of checking everything I checked the MAF plug and when I unplugged it, it rank ok. Now before I had gone up the hill, and In general, the car runs around -20-22 psi of vacuum. When I got to the top of the hill after having these proboems the car was idling around -12-10....However when I unplugged the MAF I was back to idling around -20. The car Is pretty much un-driveable with the MAF plugged in. I would venture to guess[headbang] that the MAF is bad but what I am worried about it the lack of turbo pressure. I can definitely hear it. Is this somehow electrically intertwined with the MAF. This is my first venture into forced induction land I had two MKIV VR6's, one MKII 16v, a 1978 MKI diesel rabbit, 72 914, and countless other air cooled machines. Any help would be greatly and humble appreciated.

pbcrazy
10-27-2014, 01:58 PM
However when I unplugged the MAF I was back to idling around -20. The car Is pretty much un-driveable with the MAF plugged in.
Pretty much the tell tale sign of a bad maf. What does Vag-com read at idle for the maf (g/s)?