Jeff N.

Hi,

Can you help me shortlist what might be wrong on my 86 951? Too new to these cars to have a good sense of how to run this one down.

How this started: It's been fine until a semi-spirited drive the other day. During the drive, I start hearing this "whooosh...whoosh" from under the hood. I immediately pull over and discover that the passenger side hardpipe/intercooler connection has popped off. I replace the hardpipe and from here on out is when the problem has happened.

So... I'm thinking that something blew right about the same time the pipe popped out thus the "catastrophic event" title.

Symptoms: Car will start and generally idle smoothly. Occasionally while idling, it will spit, sputter and die. Again while idling, if you touch the throttle ala to blip the engine, the car will refuse to catch and will sputter, hiccup and generally refuse to advance the RPM.

The car will drive (somewhat) but generally refuse to boost. It will advance RPM the throttle under load but not drive like you normally expect. (I have less information on how it behaves as I don't have really any road time in the car since this started.)


Here's what I've been able to check so far:

• Intercooler / hardpipe hoses for splits
• Blow off valve function + hose
• J-boot inspection
• Careful visual inspection of all the silicon vacuum hoses
• As best possibile, visual inspection of the ISV hoses
• Changed chips from MFG 1 to MFG 2 to rule out chip/DME issues
• TPS clicks on and off with throttle plate

I don't have the gear (yet) to do a pressure test of the intake system but that would seem to be a logical test.

Car has the following mods: Tial wastegate, Sci-vision MAF, Lindey boost controller. Full LR silicon hose kit. Runs typically about 15lbs of boost.

The VDO boost gauge normally shows about 18 to 20 hg of vacuum at idle. It's now showing closer to 17 to 18hg. So, something's different there and I guess that would suggest a vacuum leak.

I guess here are my questions.

• What might have 'popped' at the same time the hardpipe let go? Any suggestions on possible candidates?
• Would a slight vacuum leak at idle cause this serious of run issue? It seems like a 1 to 2 inch HG drop would be relatively minor but the size of the stumble suggests a 'big leak'. Or does it?
• Short of a pressure test, is that any way I can get to the bottom of this?

Thanks in advance for the help...

boost feen

I know its a different line of questioning but check you distribitor cap for cracks, check your rotor and all spark plugs and plug wires. Pull the rubber boots away from the spark plug end and inspect for any corrosion behind the boot. Also check the wire harness that controls injectors as these plugs and wires get corroded under the boot conectors as well! Good luck!

Chris White

Sounds like you still have a leak - pressue test the intake system. (do a search - there have been some good threads on how to pressue test the right way)

Jeff N.

..was wondering if there's any thinking on 'what to look at first' suggestions that I should ponder.

I did a lot of reading and it seems like the ISV circuit is a typical suspect (although the car idles smoothly so I'm really wondering if that's it). Obviously hard to visually check.

Car doesn't have the cycling value so that's out. Hoses are silicon and connected. Will a silicon hose split? Wastegate hoses are connected and clamped.

Prepping for a pressure test (tried to do some reading on this too but didn't come across a good summary post). Seems like you need the following:

• Plug with Shrader valve to go in end of cold side compressor hose.
• Air tank of some sort that will supply 'quiet' air to about 15PSI. Quiet so you can listen.
• Spray bottle with soapy water for leak inspection

Anything else?

Geneqco

An easy way to check for leaks is with a bottle of propane gas - if you have a blow torch, you can use it to direct the gas (unlit of course!) If you get an increase in idle speed, you have found your leak.

Jeff N.

I was looking at PET trying to figure out the layout of the misc hoses that might have been effected. (What a mess it is). I'm really starting to wonder if one of the ISV circuit hoses didn't get fubared. Here's why:

• The ISV circuit is has large diameter hoses, big enough for a "big leak"
• The ISV has a direct input into the intake manifold where a leak would make the biggest impact
• It seems 100% impossible to inspect the ISV circuit without removing the intake. As everything else looks good, this seems to be all that's left.

Any suggestions on how to inspect the ISV hoses without pulling the manifold off? PET seems to suggest there's several candidates in there. Would the propane trick work - I would think it's hard to get the nozzle close enough to a hose to change how it runs...or ??

Thinking I'm pulling the intake off here shortly.

Jeff

Geneqco

When I was testing mine I first just clalped the hose to the ISV. I later used propane everywhere... I bit of extra gas pressure from openingthe valve a bit more enabled me to get to the more difficult places.

Jeff N.

Well - pulled the intake manifold off tonight to inspect the ISV lines and other hidden do-dads. Bottom line, nothing obvious.

PO has done the venturi delete, hoses from the ISV to the hard pipe and ISV to manifold look great.
ISV itself looks near new. Internal rotor is clean.
All the misc silicon lines seem to hold pressure when individually tested.

Hmmm. Curious.

facboy

might be something unrelated you know. have you checked your maf connector? rotor and cap?

intermittent problem with either could cause the running issues you've described...i had a marginal rotor once and the car would die or stumble every now and then (until it stopped running altogether).

Jeff N.

Happy to report it's fixed. Never determined what the exact root cause was but suspect it was a big vacuum leak as several folks suggested above. Here's what I did:

• Pulled the intake manifold
• Carefully checked / resealed the vacuum lines
• Check and resealed the ISV lines
• Rebuilt the throttle body (those seals were quite crunchy)
• Rebuild the injectors (more because I had them out than anything else)

Put it back together and it now idles again with ~20 inches HG and pulls smoothly. Still having some issues keeping my hardpipes attached to the boost hoses but plan to in some nice T-clamps and that should put an end to that.

Anyways, thanks to everyone for the help!