ZR-1 Down =(

[Okiedoke]

I was starting the Z to go on a drive when it replied with a pretty resounding NO. The car started pretty rough doing a slow shaking and lurching all over. I gave it a little gas and the RPM came up. I then noticed some white smoke come out of the exhaust. The check engine light came on. I opened the hood and think I heard a small hissing sound like air coming out of a tire. I shut it down. When I walked to the back, I saw the exhaust had sprayed some black dots. I've included the photos below.

I last drove the car a week ago. It started rough like this, but I thought maybe it was because I hadn't driven the car in 4 weeks. When I stepped on the gas a little, the engine smoothed out. After a couple of minutes, it was back to normal. I'm thinking whether it may be something I might have accidentally touched when wiping down the engine 5 weeks ago. I was extremely careful though and the cloth was a bit damp, not enough to drip. So how badly screwed am I? :cry:

Here's the spray out of the exhaust:
http://i34.photobucket.com/albums/d119/harryhhsu/BlackStuff_zpslm3beuyv.jpg

Here's a closeup:
http://i34.photobucket.com/albums/d119/harryhhsu/BlackStuff2_zpseqnvt98l.jpg

[Paul Workman]

White "smoke" from one of the tail pipes is a sign of coolant getting in the combustion chamber. That may or may not be a "biggie", depending.

A more common cause is the plenum gasket or IH gasket. There is a narrow gap between the intake runner and the coolant port on both the #2 or #3 cylinder in both sides of the IH. Those not withstanding, and we're possibly talking about a head gasket...and that means the head(s) need to come off: a big job.

Let's hope it is only the plenum gasket, or IH gasket (not so likely). Before I installed gaskets from Jerry's Gaskets I went through two others in short order before striking upon Jerry's.

See what you find. Good luck!

[gbrtng]

It probably backfired and blew the MAP hose off at the back of the plenum. Check at the rear of the round thingy for a loose hose. Reconnect and the CEL will go away by itself.

[Paul Workman]

It probably backfired and blew the MAP hose off at the back of the plenum. Check at the rear of the round thingy for a loose hose. Reconnect and the CEL will go away by itself.

Yeah, good point, Glenn. Coolant leaks, in my experience, didn't set off the SES light, and looking again I DO see "stuff" from both tail his pipes, more indicative of a problem common to the entire engine - not to mention doing the simple checks first!

[Z06scentair]

Charcoal canister come apart?

[Billy Mild]

My car occasionally has that black soot come out of the exhaust as well. My car runs fine, put down 330 WHP on a dyno. My old 944 turbo did it as well. I think it is the mixture of condensation and soot breaking apart in your exhaust.

[Dime]

My car occasionally has that black soot come out of the exhaust as well. My car runs fine, put down 330 WHP on a dyno. My old 944 turbo did it as well. I think it is the mixture of condensation and soot breaking apart in your exhaust.

Mine does as well, and runs fine too. Pretty sure Billy's right; just exhaust soot.

[A26B]

I am in agreement with Paul's assessment. Condensation in the exhaust won't cause poor engine operation.

I just finished assembling mine after removing secondaries and re-porting. I always had a chronic problem with wet soot from the exhaust. The source turned out to be the injector housing to cylinder head gasket had failed around the coolant passage. New gaskets with hi-tack sealant around the port on both sides of the gasket has so far cured the problem.

The possibility also exists that the coolant port from the injector housing to plenum for T-Body heat, may be leaking into an adjacent intake port. Not as likely but still worth checking. I eliminated the coolant to the T-Body while doing this remedial work.

[Okiedoke]

It probably backfired and blew the MAP hose off at the back of the plenum. Check at the rear of the round thingy for a loose hose. Reconnect and the CEL will go away by itself.

Not that I know where this hose is, but I looked in back and didn't see anything obvious that was disconnected. I've included a picture from both sides:

http://i34.photobucket.com/albums/d119/harryhhsu/Plenum1_zpsvw0feevl.jpg

http://i34.photobucket.com/albums/d119/harryhhsu/Plenum2_zpsfrprijdh.jpg

[Dmod81]

It would be that black plastic line just to the lower right of the green connector in your first picture. It can be kind of hard to reach and reconnect sometimes.

[We Gone]

Remove the two black torx screws from the silver cover at the rear, your map sensor is under it and also held on by the two screws. (be careful not to drop them) As you lift it you will find a vacuum line hooked to the bottom, it may also be oil soaked and fit lose if you can put a small tie wrap on it. Hope its your issue if not check the lines under the front of the plenum just behind the throttle body drivers side.

[Okiedoke]

It would be that black plastic line just to the lower right of the green connector in your first picture. It can be kind of hard to reach and reconnect sometimes.

I hope this is it!! I put my finger in there to feel around. The bottom right end of the line is disconnected and had oil coming out of it. Let me see if I can feel around some more and try to get it connected.

[We Gone]

Here is what the underside looks like, if the vacuum line is off that's most likely your issue.

http://imagizer.imageshack.us/v2/800x600q90/537/c8fj26.jpg

[Okiedoke]

It probably backfired and blew the MAP hose off at the back of the plenum. Check at the rear of the round thingy for a loose hose. Reconnect and the CEL will go away by itself.

Never would have guessed there would be a loose plastic hose that slips into a hole completely unsecured, but there it is. Guess the stiffness of the plastic hose helps keeps it in there most of the time. As soon as I put it back in, she fired right up and idled smoothly. Do I need to figure out why it backfired or is it normal for that to happen once in a while?

Thanks a bunch to everyone for your help! The knowledge of folks on here is just amazing! :cheers: Man, was I sweating!

[gbrtng]

Never would have guessed there would be a loose plastic hose that slips into a hole completely unsecured, but there it is. Guess the stiffness of the plastic hose helps keeps it in there most of the time. As soon as I put it back in, she fired right up and idled smoothly. Do I need to figure out why it backfired or is it normal for that to happen once in a while?

My 91 sneezes every so often and blows the MAP hose off. Some folks secure the hose but my best bet is to leave it loose so something harder to fix doesn't split/break/fail. Some claim that releasing the key from cranking too early causes a backfire - not on mine. It's just haunted ...
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