Ok, my detonation's just getting worse. For the first 5 minutes of driving the car, there are no problems. The car smells really rich, more like unburnt fuel than burning oil.

But once it's warmed up, it detonates LOUDLY as soon as you go into boost. If you stay on it and go a little above 10psi, it goes away mostly. Car is totally stock, 95 TSi.

Things I've done:
Replaced Plugs twice (Champion and NGK)
Replaced Wires twice (Magnecore and Denso)
Replaced O2 sensor twice
Replaced Knock sensor (OEM new)
New Fuel filter
Soaked injectors in Acetone for 2 hours
Seafoam- 1/2 bottle thru intake, and in gas tank.
New PCV valve
Timing light (with brown wire grounded) says engine is about 4* retarded from stock spec at idle.
Boost leak test (will be retesting this) showed only tiny leaks.
Compression test 180-180-150-180 (was 180 across when detonation first started)
Oil in cylinder brings all to 180 again.

Things I haven't replaced
Crank Angle Sensor (requires removal of timing belt on a 1995)
Cam Angle Sensor (requires removal of timing belt on a 1995)
Injectors themselves
MAF/MAS
ECU
Fuel Pump
Fuel Pressure Regulator (stock fuel rail)
Ignitor Pack
Injector Resistor pack
Coil Pack

I've run out of ideas, short of replacing every damn sensor and part remotely related to the MFI system. Help?

That 150 is trouble. Looks like you toasted some piston rings. You are running stock boost on the stock turbo right? That pretty much can't create that much knock unless you basically have no fuel at all.

Either way, you need a rebuild. More than a 10psi difference between cylinders is really bad.

Do you have a boost gauge? Maybe somehow the car is running way more boost than it should be.

Yeah I know it's dead, but there's no way I'm putting in the time to rebuild it unless I can find the source of the ring-killing. The compression was perfect when this problem started, so it's a symptom, not a cause. I expected the rings to let go sooner or later with how much detonation I'm getting.

As far as boost, it's totally stock. Stock T25, stock solenoid, hitting max 15psi boost then drops to 12psi. The worst detonation is at like 1-5psi boost on part (15-20%) throttle.

So you think replace all the injectors? Having only one cylinder let go first makes it seem like one of the injectors is bad. But then I tested each with 9v battery, they all click normally. Also tested the resistance and they're all in spec.

Wow, you pretty muched replaced everything control wise, even down to the ecu.

datalog it yet?

Member # 751


FOUNDER of the Central Cali chapter of 2GNT!
(I got kicked out after I refused to go Cow tiping) - Hehehe you know who this is for

Yeah you really need a datalogger to figure out what's going on there.

Good luck.

I didn't replace the ECU Chamuko- see "things I HAVENT done"

Datalogger results:

O2 @ WOT: .96-1.0v!!! Averages about .98

LTFT Idle: 5.5%
LTFT WOT: 7.8%

STFT - 0-2%

Advance Idle: 10*
Advance Max WOT: 19*
Advance Min WOT: 11* (with audible knock)
Advance Max Part throttle: 9* (with audible knock)
Advance Min Part throttle: 4.5* (with severe knock)

MAF Idle: .48 lb/min
MAF WOT: 21.5 lb/min

Coolant temp: 220*F

Intake air temp: 90*F

The knock sensor is definitely working because it pulls out a good 10 degrees of timing when knock starts. Still no CEL's, no stored codes.

Any ideas?

Brand new injectors didn't fix it.

Gotta be MAS, timing, or the crank angle sensor.

I gave up and sold the car. Problem solved.