puff of smoke and service engine soon light appears

[nrangerZR-1]

Well - I discovered the solution to the problem I described below. After reviewing my GM manuals for a moment, I took a close look at the EGR valve and the surrounding plumbing and realized that 2 vaccum lines had popped off. I reconnected them and everything works great. It idles well and the service engine light has been extinguished.

Time to take the glass top off and go for a morning ride!
Robb


_______________________________________________________________

Good morning everyone,

Last night I turn the key to crank the engine on my 91 ZR-1 and something very strange happened. The engine turned over just fine, but there was a "pop" sound from under the hood. I turned the key off before the engine actually started and notice a little smoke coming up from under the hood. It was gone pretty quickly and I could not identify the source. I restarted the car and it did not occur again. It idled rough at first, but once we were under way everything ran great. Well, the service engine soon light was now glowing brightly.

I know this is pretty vague, but any ideas - did I lose the EGR valve or a sensor? What could have caused the smoke? Maybe a small backfire through the exhaust manifold? I have read a number of threads regarding the light, but could not find the "smoke" event described here anywhere. I am a novice with regard to working on the LT5, so go easy on me.

Just cranked her this morning and the light stays on and I can notice a change in the smell of the exhaust.

Any suggestions would be much appreciated.

Many thanks,
Robb

 

[Rob]

Robb,

Glad everything worked out for you. Now get out there and go exercise those secondaries!

 

[nrangerZR-1]

They have been fully exercised and appear to be in tip top shape!

 

[Jeffvette]

If you've got a EGR valve, you have a very rare 91 ZR-1.

More than likely the hose you are talking about is the one for the map sensor. It's on the back side of the plenum.

 

[Hib Halverson]

Jeffvette is right.
A 91 has no EGR valve and, even if it did, it would not have two vacuum lines connected to it. What you were looking at was the MAP sensor.

 

[nrangerZR-1]

Thanks Hib and Jeffvette.

This forum, and your respective expertise, is invaluable.

 

[fhturner]

Last night I turn the key to crank the engine on my 91 ZR-1 and something very strange happened. The engine turned over just fine, but there was a "pop" sound from under the hood. ... It idled rough at first, but once we were under way everything ran great. Well, the service engine soon light was now glowing brightly.

Well, this is weird. I was gonna post nearly the exact same question. I drove my Z last Monday (5/2) for the first time in several weeks. Probably put 80 miles on it Monday night. Then, went to crank it up Tuesday morning and heard a small "pop." After this, the engine would fire, but after doing its initial post-start "rev up", it would settle all the way down through idle RPM and just die. Sounded normal, just wouldn't stop dropping RPM at the idle level. I finally got it to stay running after revving it quite a bit, and was able to get home. But, the SES light was on all the way. At home, I turned it off, then refired to see if the SES light would still be there. It was. Should I be looking for the same culprit as Robb?

Thanks,
Fred

 

[Jeffvette]

Damn Fred, you need to stick to the C5's


I'll give you a call in a few

 

[nrangerZR-1]

Fred - let me know if your problem was the same as mine.

 

[Jeffvette]

It was.

 

[fhturner]

It was.

Hey, hey-- he asked me...

Seriously, Jeff fixed me right up. It was a vacuum hose between the MAP and the rear of the plenum that had popped off. After enduring much b*tching and moaning on my end about how my oversized hands wouldn't fit down behind the plenum, Dr. Flint guided me to where the L-shaped hose was, and I then saw that it had come off the back of the plenum. Pushing it back on there cured the problem, and no more SES light for me. Of course, as I told Jeff, I did have to make a 20-minute run to make sure it was fixed (and this was at 12:30 at night!)...

L8r,
Fred