intermittent boost problem

alphaseinor

TDI Innovator Vendor , w/Business number
Joined
Jul 30, 2006
Location
Denton, TX
TDI
'03 Jetta TDI 780,000 miles (totaled out), 01 Audi TT 225 Quattro 230,000 Miles (runs great!), 00 Cabreetle Beetle dash, ALH & MK4 harness Swap
Okay this is a customers car, I'm a little stumped since I haven't seen this problem before

02 beetle ALH

here's what I know:
the vehicle will accelerate fine when cold

it will accelerate fine from a stop, so long as you don't let up on the throttle

if you lightly roll on the throttle boost actual will follow specified relatively closely, only if you haven't shifted into 2nd (automatic)

if you roll to about 2,000 RPM then punch it, the engine will make a dieseling noise and blow out a ton of smoke while boost hangs at atmospheric pressure until about 3000 RPM, then slowly raise to about 2.1 bar, settling at about 1.9bar

If you unplug the MAF the vehicle drives fine.

here's what the customer has already done to the vehicle:
No chiptune
Sprint 520's
new MAF (also tried one from my personal car, same problem)

Here's what I've checked
Pump voltage jumps to 2.2v when the problem is occurring.
timing is at the middle of the graph when warm
IQ is at 2.3
Boost actuator is holding vacuum, and is actuating between 5hg and 20hg, about 3/4" travel
intake is clean


Thanks everyone!
Any ideas?
 

Curkkic

Veteran Member
Joined
Feb 20, 2007
Location
Colorado, Greeley
TDI
None any more ;(
sounds like a MAF. probably harness side. Spray some contact cleaner in the boot? mine had a similiar problem do you have a flow module for what the MAF is reading? i average about 86 in mine anything below about 62 at heavy accel will indicate MAF problems
 
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