Folks,

My 1986 745T is on the fritz yet again....I had had a small exhaust leak when one of the gaskets between the head and the exhaust manifold decided to die on me, which slowly progressed into a big exhaust leak. That leak is now fixed. Needless to say, this was causing slight (but not as huge as one might imagine) performance issues. With the leak fixed and the turbocharger spinning up, there was more pressure on the system than ever. When my mechanic had pulled my turbo, he'd noticed that the fresh air hose that ran between the airbox and the input of the turbocharger was, how shall we say, a bit decrepit. I've since replaced this $175 hose, as it definately had a hole in it. I also found a similar hole worn over time through the rubber tube which runs from what appears to be (what I think is) the vacuum-controlled wastegate actuator and the large 2ish inch hose that is the output of the turbocharger.

I assumed I had the problem licked, drove the car for an hour or so, and as I pulled into my driveway, the confounded thing started doing the following things again:
1. Running rich
2. Backfiring if I put my foot into it at all
3. Can't exceed about 45/50 miles per hour
4. boost will only build EXTREMELY slowly...if I put my foot into it at all, it's a lost cause, but if I nurse it along, I can get up to 45/50.
5. All this is accompanied by what sounds like a backfire sound (if I put my foot into it at all)
6. This is a completely intermittant problem.
7. Rough, seeking idle, but only sometimes

From a cold start, the problem does not manifest itself.. In fact, in the several times I've gotten the problem TO manifest itself, it's been AFTER the car has had a long, hard slog, and has performed marvelously... I'm quite frustrated and have checked ALL rubber for signs of extreme wear/cracking/etc for obvious reasons, and have found no other problems, including on output side of the intercooler, where I did find yet another problem with the rubber and replaced the rubber accordingly. I also thought it was possible that the little wastegate-controller thing that is bolted to the front of my head and interconnects the output and input to the turbocharger was malfunctioning, so I disconnected the vacuum to it, plugged the line, and, after a drive such as the one defined above, this problem would still occur. Consequently, I'm relatively sure that's not the problem, but you never know.

HEEEEEEEEEEEELLLP!!! I'm pulling my hair out over here....

Alex Perez


Does *ANYONE* have any suggestions?