Hi All,


Yesterday I was driving and the strangest thing happened. The car began severely overboosting when on full throttle. It was fast enough and hard enough to cause audible detonation. It began after several WOT accelerations at "normal" boost levels. I'm not sure what defueling feels like in this car, but the car didn't feel like it was defueling and there was no CEL at any time.

After gingerly experimenting in 2nd, 3rd, and 4th gears, I could easily, repeatedly induce "overboost" with throttle anything past 3/4 travel. I was able to modulate the overboost with the throttle to eliminate any audible detonation (wary, of course, that I was likely still detonating inaudibly).


After dropping the kids off, I opened the hood to inspect for any loose/cracked/broken/disconnected hoses going to and from the turbo and wastegate. Nothing. Before shutting the car off, I went around the block a few more times and I was predictably able to control the boost and command this wicked overboost. Suddenly the need to install my ipd boost gauge (just purchased last week) became real!


Alas, was it all a dream? I shut car the car off and lost a lot of sleep last night trying to figure out why. Today I start the car and Mr. Hyde has returned to being Dr. Jeckill. No overboost. Nothing. Like it never happened.


I've had the car ~ 1.5yrs and this has never happened before. In full disclosure, I had all the manifold studs/nuts and turbo-to-exhaust flange bolts replaced a couple of weeks ago as well as the o-ring sealing the oil line to the block. Could the technician have knocked something loose?


Help!! Any ideas or comments of similar experiences are welcome.


Don't get me wrong, it felt DAMN good...but not at the risk of grenading the engine, melting pistons, etc.


Thanks
Tim

 

first thing I'd have checked is that vacuum line to the wastegate. also make sure the wastegate plunger can be moved freely (its under some spring pressure, but with a pair of longnose pliers or whatever, you should be able to work the plunger back and forth and feel the waste gate valve spring.

what did the turbo gauge on the dash show during this? was it pegging to the right? mine rarely goes above about halfway between straight up and the end of the scale.

 

Thanks for the tips, Pierce. Wilco and advise.


To answer your question, yes the factory boost gauge was tracking the "butt-o-meter" pretty well. Typical max (uncalibrated) boost has the gage needle half way over into the +PSI range, but in this overboost condition, I could nearly peg the needle to the right.


It does make me suspicious that this happened just after the recent work...


Also, I owe you a thanks on another thread, but won't divert this one.


Tim