Help with some problems with my 92 - ZR-1 Net Registry Forums

jcruz · 01-25-2021

Hi all,

After a few years I'm finally able to spend time troubleshooting some problems with my 92. About 43,000 miles. I've had the car 9 years and only put about 2000 miles on it.

I'm sort of stuck on what the problems are and how to get them fixed, so I'm looking for any information, leads, advice, ideas, and other helpful information to make some progress.

Gathered some pics & vids last weekend when I had a chance to get the car up on a lift.

Issue #1 -- my car stinks

I'm having some sort of exhaust problem(s)...the exhaust stinks, so bad my wife won't ride in the car any more. The smell is bad in the cabin and, as you can imagine, worse when sitting at a light. The kind of smell that stays on you and can give you a headache. Seems like I have an exhaust leak of some kind.

Here's a short vid of smoke from the exhaust:

https://vimeo.com/504324317

I get a LOT of condensation out of the muffler. Black:

Also, I'm wondering if there might be something wrong with the catalytic converters, so I took a vid with the engine running. Is this useful in any way?

https://vimeo.com/504323929

Issue#2 -- Clunk/click in the rear somewhere

When the car is cold and moving, I hear an intermittent clunk/click that's driving me crazy. When it happens, you can feel it in the steering wheel. When things warm up, like by the time I get out of my driveway, problem goes away. I first thought it was the brakes binding but I think now it might be a bad U joint or bad spline? The half shafts looked okay but the rear seal seems to be leaking badly. We checked the rear fluid level and to my untrained eye, this oil looks like it really needs to be changed:

Here's a couple pics around the rear seal area. The cover and the surrounding area were very wet.

Should I plan on replacing the seal and seeing what else might be wrong when I'm in there?

Issue#3 -- car stumbles under hard acceleration

Not sure where to start with this one. The car stumbles/bucks badly no matter what speed. With the power key on it's not quite as noticeable. Idles fine and runs smoothly under normal driving conditions.

I had the coils replaced a few years ago. That helped a bit, but didn't solve the problem. I've never changed the plugs, had the injectors replaced, or anything else done on the motor.

What can I do to help diagnose & isolate this issue?

Issue #4 -- what's this port?

A question, really. This port looks like it needs some kind of hose attached. There's a matching port on the other side of the plenum. It looks like someone re-routed the hose so it now goes around the front of the plenum? Wondering what should be hooked up to this port and if it might be contributing to issue #3?

Thanks in advance for any information you can provide!

John

-=Jeff=- · 01-25-2021

Issue 4.. is was for Coolant to keep the TB warm for cold days.. it is bypassed on your car.. typical mod..

Issue 2.. the front pinion seal seems to be leaking, Might be good to have the differential checked when the seal is replaced, assuming the unit needs to come apart for the replacement of the seal. The clunk could be a u-joint

jcruz · 01-25-2021

Quote:

Originally Posted by -=Jeff=-

Issue 4.. is was for Coolant to keep the TB warm for cold days.. it is bypassed on your car.. typical mod..

That makes perfect sense: the car came out of FL originally, but I bought it from someone in NY who was road racing the car. Car is now back in FL where it belongs ;-)

EthanCohen75 · 01-25-2021

Regarding issue 3, maybe check the link below:
http://www.autotap.com/problem4_engine_hesitates.asp

In short, these could be the issues:
Mass Airflow Sensor
Fuel Pump - doesn't give enough fuel to the engine
Throttle position sensor
Dirty/failing fuel injectors - might be dirty and have to be cleaned/exchanged.

dredgeguy · 01-25-2021

How old is the gas in the car? Could old gas account for condensation and smell? Old gas stinks.

A26B · 01-25-2021

The black, sooty condensation from the exhaust at first startup of the day is symptomatic with leaking injector housing gaskets at the cylinder head interface. Coolant seeps into adjacent intake port, accumulates & blows out on first cold start of the day.

WARP TEN · 01-25-2021

Question: Does your car have catalytic converters or have they been removed for headers? It looks like your exhaust is stock from the video but I also had a stock system from headers back on my '95 but removed cats to go with headers. I also regularly had a bad smell on startup but that was the old smell of the '50s and '60s--before cats, when we tuned cars by smell and the look of the smoke out the exhaust. If your car does have cats, is it possible they have become non-functional? If your cats are fine and you think you have an exhaust leak it would have to be ahead of the cats to produce the smell you describe, I would think, which would mean headers. Certainly an exhaust leak should be corrected. Also, my take on the "smoke" and moisture from the mufflers is that it is simply condensation and entirely normal. I also had it. The pipes are lower than the muffler outlets for much of their length and a lot of moisture can accumulate in them. Drive for an hour or so then see if you get much on a cold start afterwards. As to a clunk in the suspension somewhere, I also had such a clunk especially when I backed out of my slightly inclined driveway, afterwards normally I wouldn't notice it. While everything looked fine, Marc changed the sway bar bushings and that solved it--no more clunk. My car had only 30k miles on it but the bushings just got old and hard. You indicated you felt it in the steering wheel so maybe front bushings need a look. --Bob

secondchance · 01-25-2021

Issue #2:

If clunking noise is when you go over left to right uneven road (car swaying left to right), I would suspect worn out rear sway bar bushing. I recommend urethane bushing since OEM rubber bushing will fail quite fast.

If clunking noise is from directional change as in forward, stop, reverse, most likely driver side rear bearing hub being torqued to 160 lb-ft. This was revised to 190 lb-ft by Chevrolet.

jcruz · 01-25-2021

Quote:

Originally Posted by EthanCohen75

Regarding issue 3, maybe check the link below:
http://www.autotap.com/problem4_engine_hesitates.asp

In short, these could be the issues:
Mass Airflow Sensor
Fuel Pump - doesn't give enough fuel to the engine
Throttle position sensor
Dirty/failing fuel injectors - might be dirty and have to be cleaned/exchanged.

I'll start researching each of these areas....many thanks

jcruz · 01-25-2021

Quote:

Originally Posted by dredgeguy

How old is the gas in the car? Could old gas account for condensation and smell? Old gas stinks.

I run the car regularly enough and the gas is not too old. But, good idea...I'll run through a tank.

01-25-2021	#5
dredgeguy Join Date: Aug 2012 Location: Ellicott City, MD Posts: 1,725	Re: Help with some problems with my 92 How old is the gas in the car? Could old gas account for condensation and smell? Old gas stinks. __________________ Charlie __________ Dredgeguy WAZOO Member 1992 Bright Red/Black ZR1 #246 Dana 4:10 gears Polished LT5 by Haibeck Polished Fikse FM5's with Michelin Pilot Sport 2 Stainless Works headers and cats with Corsa

01-25-2021	#6
A26B Join Date: Dec 2003 Location: Arcadia,OK Posts: 3,396	Re: Help with some problems with my 92 The black, sooty condensation from the exhaust at first startup of the day is symptomatic with leaking injector housing gaskets at the cylinder head interface. Coolant seeps into adjacent intake port, accumulates & blows out on first cold start of the day. __________________ Jerry Downey JERRYS LT5 GASKETS & PARTS http://www.jerrysgaskets.com 1994 *ZR-1*, Black/Black, Lingenfelter Aerobody, 416cu in, 3.91 gears, coil-over susp, Brembo brakes, etc. 2016 Black-Red, 3LT-Z51 Auto 8-speed.

01-25-2021	#7
WARP TEN Join Date: Apr 2007 Location: Lake Bluff, IL Posts: 2,109	Re: Help with some problems with my 92 Question: Does your car have catalytic converters or have they been removed for headers? It looks like your exhaust is stock from the video but I also had a stock system from headers back on my '95 but removed cats to go with headers. I also regularly had a bad smell on startup but that was the old smell of the '50s and '60s--before cats, when we tuned cars by smell and the look of the smoke out the exhaust. If your car does have cats, is it possible they have become non-functional? If your cats are fine and you think you have an exhaust leak it would have to be ahead of the cats to produce the smell you describe, I would think, which would mean headers. Certainly an exhaust leak should be corrected. Also, my take on the "smoke" and moisture from the mufflers is that it is simply condensation and entirely normal. I also had it. The pipes are lower than the muffler outlets for much of their length and a lot of moisture can accumulate in them. Drive for an hour or so then see if you get much on a cold start afterwards. As to a clunk in the suspension somewhere, I also had such a clunk especially when I backed out of my slightly inclined driveway, afterwards normally I wouldn't notice it. While everything looked fine, Marc changed the sway bar bushings and that solved it--no more clunk. My car had only 30k miles on it but the bushings just got old and hard. You indicated you felt it in the steering wheel so maybe front bushings need a look. --Bob __________________ 2016 Long Beach Red Z06 #10281 "POPS Z" 1995 Polo Green #409 "WARP TEN"--Haibeck 350/510 package, 4.10s, Hurst, Stock Exhaust with QTP Cutouts --Sold but still running strong 1993 Quasar Blue #161 "HIL KING" --Sold but still running strong, now with more than 120,000 miles 1967 Marlboro Maroon/Saddle Corvette Coupe 300 hp/4-spd --Sold a long time ago ZR-1 Net Registry Founding Member #95 NCM Lifetime Member Favorite Quote--Attributed to Mickey Thompson: "Too Much Horsepower is Almost Enough" Last edited by WARP TEN; 01-25-2021 at 12:13 PM.

01-25-2021	#8
secondchance Join Date: Aug 2006 Location: McLean, VA Posts: 3,727	Re: Help with some problems with my 92 Issue #2: If clunking noise is when you go over left to right uneven road (car swaying left to right), I would suspect worn out rear sway bar bushing. I recommend urethane bushing since OEM rubber bushing will fail quite fast. If clunking noise is from directional change as in forward, stop, reverse, most likely driver side rear bearing hub being torqued to 160 lb-ft. This was revised to 190 lb-ft by Chevrolet.

01-25-2021	#1
jcruz Join Date: Mar 2010 Location: Fort Myers, FL Posts: 343	Help with some problems with my 92 Hi all, After a few years I'm finally able to spend time troubleshooting some problems with my 92. About 43,000 miles. I've had the car 9 years and only put about 2000 miles on it. I'm sort of stuck on what the problems are and how to get them fixed, so I'm looking for any information, leads, advice, ideas, and other helpful information to make some progress. Gathered some pics & vids last weekend when I had a chance to get the car up on a lift. Issue #1 -- my car stinks I'm having some sort of exhaust problem(s)...the exhaust stinks, so bad my wife won't ride in the car any more. The smell is bad in the cabin and, as you can imagine, worse when sitting at a light. The kind of smell that stays on you and can give you a headache. Seems like I have an exhaust leak of some kind. Here's a short vid of smoke from the exhaust: https://vimeo.com/504324317 I get a LOT of condensation out of the muffler. Black: Also, I'm wondering if there might be something wrong with the catalytic converters, so I took a vid with the engine running. Is this useful in any way? https://vimeo.com/504323929 Issue#2 -- Clunk/click in the rear somewhere When the car is cold and moving, I hear an intermittent clunk/click that's driving me crazy. When it happens, you can feel it in the steering wheel. When things warm up, like by the time I get out of my driveway, problem goes away. I first thought it was the brakes binding but I think now it might be a bad U joint or bad spline? The half shafts looked okay but the rear seal seems to be leaking badly. We checked the rear fluid level and to my untrained eye, this oil looks like it really needs to be changed: Here's a couple pics around the rear seal area. The cover and the surrounding area were very wet. Should I plan on replacing the seal and seeing what else might be wrong when I'm in there? Issue#3 -- car stumbles under hard acceleration Not sure where to start with this one. The car stumbles/bucks badly no matter what speed. With the power key on it's not quite as noticeable. Idles fine and runs smoothly under normal driving conditions. I had the coils replaced a few years ago. That helped a bit, but didn't solve the problem. I've never changed the plugs, had the injectors replaced, or anything else done on the motor. What can I do to help diagnose & isolate this issue? Issue #4 -- what's this port? A question, really. This port looks like it needs some kind of hose attached. There's a matching port on the other side of the plenum. It looks like someone re-routed the hose so it now goes around the front of the plenum? Wondering what should be hooked up to this port and if it might be contributing to issue #3? Thanks in advance for any information you can provide! John __________________ 1992 #043, Aqua/Gray 40k miles

01-25-2021	#2
-=Jeff=- Join Date: Jul 2007 Location: Bartlett, IL Posts: 7,173	Re: Help with some problems with my 92 Issue 4.. is was for Coolant to keep the TB warm for cold days.. it is bypassed on your car.. typical mod.. Issue 2.. the front pinion seal seems to be leaking, Might be good to have the differential checked when the seal is replaced, assuming the unit needs to come apart for the replacement of the seal. The clunk could be a u-joint __________________ 1990 Corvette ZR-1 #1051 Watson Headers (2" Primary) - Flowmaster Cats - Borla Catback Late Model IH - Plenum Coilovers - 4.10s Custom Interior NCM Lifetime Member #978

01-25-2021	#4
EthanCohen75 Join Date: Jan 2021 Location: Poland Posts: 1	Re: Help with some problems with my 92 Regarding issue 3, maybe check the link below: http://www.autotap.com/problem4_engine_hesitates.asp In short, these could be the issues: Mass Airflow Sensor Fuel Pump - doesn't give enough fuel to the engine Throttle position sensor Dirty/failing fuel injectors - might be dirty and have to be cleaned/exchanged.