Hi Folks,

I've been a lurker here for ages, but have come across an issues I can't seem to find resolution for in the archives.

For starters, I've got a early 1999TQM with ~150k, and no engine mods. This story may end up a bit long winded, but bear with me.

This all started about a month ago. I noticed as I was going up a hill that I wasn't really accelerating, even when I was floored. I noticed (via my boost gauge) that I was only pushing 3-4 PSI. Previously, I had been averaging 6-7. Things quickly got worse, and I started hearing the dreaded "dentist drill" noise.

So, I had a friend swap the turbo with another (presumably good one) that had been sitting for a while, approximately two weeks ago. I pick up the car, and it boosts up to 5-6, and has a distinct, but different noise. This noise sounded pressure escaping somewhere. At any rate, it was very noisy, and I tried to stay out of the boost while hoping the turbo would re-"break in."

This week, things deteriorated rather quickly. I went from 5-6 PSI, to 3-4, to 1 to 0. 0 PSI was yesterday, and it took me about 4 miles on the freeway to get up to 45 mph . As I'm limping home from work, I take a right hand corner at ~30 mph, attempting to maintain speed. All of a sudden, the boost rockets up to 15 PSI, and I damn near hit the median.

So, I pull into the driveway, let the car cool off, and then put it up on jack stands. I take a look at as many of the intake hoses I can reach, checking to ensure they're all on tight. I didn't notice any gaping holes in anything. In addition, after pulling the turbo inlet hose, the turbo appears to have ZERO shaft play.

I put it all back together, and go for another drive. The car feels like a freaking rocket. I took it easy, not wanting to go over 15 or so PSI. It seems to be jerking rather dramatically at partial throttle (unless I put in the clutch a little earlier than I would normally to shift).

I pulled the codes, and had a P1555 code. Judging by my research, this seems to be related to going past 14 PSI.

I can't imagine that this condition is great for the engine (though it is the first time I've ever though of the car as remotely fast ), so I was wondering if anyone had any ideas on what may be causing this. Maybe a bad n75 valve? I'm at a bit of a loss here.

--chris

 

It would seem that your wastegate was sticking or stuck, eventually enough pressure finally broke off the wastegate arm and now there isn't any regulation. You would need to pull the turbo off to see the broken arm. You can weld it back on (which ive seen before, cough onepoint) or change the turbo for a NEW one.