The expected happened: 951 help needed, losing boost

AaronM · 07-05-2005, 05:44 AM

Car ran great yesterday, had a blast running around with friends on the 4th. Got up this morning, 3:30 am, driving to work (bloody having to trade in European markets), hit the on-ramp and start accelerating only to get a wooshing sound and no power. Engine runs smoothly and everything's grand as long as I keep manifold pressure at or below atmospheric. Anything over 1.0 Bar on the dash guage (0 on the mechanical guage) seems to be being bled off and the car just stops making power. Feels like it's in overboost mode.

Car has a mechanical boost controller, no cycling valve, GURU chips, K26/8, and a 3.0 bar FPR. It's not running hot and checking it in the parking garage when I got to work didn't reveal excessive heat above the turbine housing so I don't think the turbo is cooked.

Cliff's Notes:
'86 951, modded, K26/8, GURU chips/boost control, no CV, 3.0 Bar FPR.
Ran great yesterday.
This morning the car will not build boost past atmospheric, wooshing sound of pressure being vented after that.
Runs perfectly off-boost.
When boost is being vented, car feels like it's hitting a rev-limiter.

Pretty sure that the car is somehow reading overboost mode, but not sure what would be causing it. There were no warning signs that I could tell of and the car checked out good locally. (Guess I really should have gone to Britwrench and Ronin for the PPI instead of another source.

)

Lawrence Coppari · 07-05-2005, 06:31 AM

I suspect the BOV has come off or the little vacuum/pressure lead on its top came off. A positive pressure leak will permit the BOV to open.

The BOV nipple should not pass gas. Also check for other leaks in system. You may also have a split pressure pipe either coming out of the compressor or one of the rubber connecters at the intercooler. The rubber connnector to the throttle body is rather stout so it is the least likely to break.

AaronM · 07-05-2005, 06:47 AM

I'll take a look when I get home this afternoon, thanks. The wooshing noise seems to be coming from the bellhousing area, but it's hard to tell with road noise and all the rest.

I would have expected something more like a weaker N/A without boost pressure, but I guess it just dies completely eh? There is pretty literally no power once the venting starts.

AaronM · 07-05-2005, 04:32 PM

Heh, boy do I feel stupid...

Throttle body connector. No rips or tears, but it popped itself out of the hose clamp which wasn't on straight. The car gods are smiling on me.

bryanthompson · bryanthompson's Garage

you better buy her something expensive now, just to make sure you're in the clear for awhile.

AaronM · 07-05-2005, 04:46 PM

Quote:

Originally posted by bryanthompson
you better buy her something expensive now, just to make sure you're in the clear for awhile.

Well, she drew blood while I was putting the hose clamp back on (so many tiny little puncture scars on my hands from cars and motorcycles...) so I think the sacrifice has been made. If not, well, she has new tires coming in a month or so anyway.

legion · 07-06-2005, 04:42 AM

I'm glad to hear this worked out.

I still have the original BOV in my car. It's on the list for next year, and I haven't had any problems, but it still concerns me.