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Clutch or something worse?

Old 08-14-2018, 01:35 PM
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wes_wes101
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Default 94 Coupe mystery problems

I've had my 94 6 speed for about 3 months, and things have been great.
About 3-4 weeks ago, I felt some lurching, maybe the clutch slipping, as I pulled onto an interstate in 6th. I went down to 5th, it stopped, and I returned to 6th after I got to higher speed. I thought that I had gotten close to stalling it by accident, but maybe the clutch was slipping? I dont really know exactly what a slipping clutch feels like.
A few mornings ago I run an errand, and I pull into a parking lot after about 10 miles of interstate/back road driving. It felt like it was going to stall and the vette was shaking as I drove around in 1st looking for a parking spot. It never shakes, it has a very smooth idle, so this really freaked me out. I let it sit for an hour, crank it up, and its still shaking at idle. With some throttle it smooths out at about 1500-2000 rpm. Starting from a standstill, it feels like its going to stall even with revving it to 2000, which is way more than normal. I drive home slowly, keeping the rpms up so it doesnt shake so bad. Once home, I rev it with the door open to get a good listen, and theres a rattling sound when it returns to idle from a higher rpm. Then I notice blue smoke coming from the hood, so I turn it off and open the hood. The smoke was coming from between the back of the engine and the firewall. It smoked steady for 5 minutes, and it was heat ticking from under the car the whole time.
Also, the clutch pedal engages high, about the top 2 inches, since I've gotten it.
So did I just really burn up my clutch and need a new one, or is something much worse going on?
Sorry if thats long winded, I just wanted to get all the info out there.

Last edited by wes_wes101; Yesterday at 11:35 AM.
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Old 08-15-2018, 09:17 AM
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MatthewMiller
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I don't think this is a clutch issue. A clutch going bad won't stall the engine - it's the exact opposite, such that the engine never quite gets the full load and it "flares" it rpm when you shift. The clutch pedals on these cars tend to engage pretty high regardless, even if they are in perfect condition. The blue smoke could just be an oil leak from the "china wall" at the back of the engine. Could be a lot of things. It sounds like there is an issue with your engine if it feels like it is going to stall. You're going to need to trace that smoke more accurately, and start running basic diagnostics on the problem.
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Old 08-15-2018, 09:55 AM
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QCVette
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It doesn't sound like a clutch to me either.

It sounds like an engine miss. If it unloaded only smooths out at 1500-2000 rpm, that is an engine issue, not clutch. Feeling like stalling and a rattle noise also sound more like an engine issue than clutch. Any check engine light?

A slipping clutch will show up under load when the engine revs without accelerating the car to match. It will then take a second or two for the speed to catch up with the motor speed. In other words, the engine flares up more than it should for the vehicle speed. Usually it will occur in higher gears while under load and may not show up in the lower gears.

Good luck.

PS.
Welcome to the forum.
Good choice on the '94 6 speed. I have had two of them (a blue one when new, and later a white one.)and loved them.
We all like pictures too, so show us your '94.

Last edited by QCVette; 08-15-2018 at 10:00 AM. Reason: spelling
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Old 08-15-2018, 10:10 AM
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Originally Posted by wes_wes101 View Post
Then I notice blue smoke coming from the hood, so I turn it off and open the hood. The smoke was coming from between the back of the engine and the firewall. It smoked steady for 5 minutes, and it was heat ticking from under the car the whole time.
Have we checked the oil and transmission fluid level?
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Old 08-15-2018, 11:19 AM
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Check fuel pressure. Do the ALDL jump wire procedure and write down any codes, report back.
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Old 08-15-2018, 07:10 PM
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The rattling sound could be explained by the DMF/ZF6 producing extra rattles due to the rough running engine. The ZF6 isnít exactly a quiet trans even on a smooth running engine so any roughness is going to exaggerate the noise. Sounds like 2 problems, oil leak - as others have said, China wall or oil sensors and some other issue causing rough running, my guess would be ignition issue but could be fuel or something else too. You have some diagnosing to do. Gettting your hands on a FSM is a good place to start.
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Old 08-16-2018, 06:39 PM
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wes_wes101
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Thanks for the leads everybody! Oil is full, but I know there is a slight leak in the rear main seal that my mechanic spotted, but it is a very slow leak, maybe a drop or two a week. And at this point I agree, I think its a miss. I have no check engine light. I guess I'll have to figure out how to run the codes.
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Old 08-16-2018, 08:22 PM
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1993C4LT1
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It's stupid easy to scan codes on these cars. Google: how to scan codes 1994 corvette. I believe you have to put a paper clip in pins A&D. But I'd look it up to be sure. No need for a code reader.
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Old 08-16-2018, 08:24 PM
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Also, don't start the car when you are scanning for codes. Key on, engine off only.
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Old 08-16-2018, 10:43 PM
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Paul Workman
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One question: Does the "almost stalling" and shaking, etc, STOP when you press the clutch to the floor, yet the engine sounds fine with the clutch depressed?

Auto Zone has a scanner that can scan OBD--I ECMs. Disconnect either battery terminal for 30 seconds at least ( the negative one is the easiest to get to), to clear the codes before you have it scanned. Then reconnect, crank it up and see what new codes pop up. Then we'll talk.
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Old 08-16-2018, 10:51 PM
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Going to Auto Zone to get codes scanned is a waste of time, IMO.
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Old 08-17-2018, 05:51 PM
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Old 08-17-2018, 05:59 PM
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Check spark plugs & wires
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Old 08-24-2018, 12:46 PM
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Paul Workman
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Originally Posted by 1993C4LT1 View Post
Also, don't start the car when you are scanning for codes. Key on, engine off only.
That depends on the situation. Sometimes scanning while driving is the only way to find certain errors.
The only way I could find an intermittent O2 sensor issue was to scan it while driving it.
The scanner had an "Event" function. That allowed the user to press a button during whatever was wrong was occurring. and the scanner would capture a block of sensor readings before and after the "event".
In my case, an O2 sensor was intermittently shorting out - fooling the computer into assuming that side had gone full LEAN. And, the fun part was it often didn't throw a code! Driving with the scanner plugged into the ALDL port was the only way I caught the problem.


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Old 10-08-2018, 03:48 PM
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wes_wes101
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Ok, sorry for the long delay, but we've been looking at a bunch of stuff on the Vette trying to figure it out. We (my friend who is a corvette mechanic and has a shop in his backyard and I) hooked up the scanner and got no codes. We have replaced the cats, which were nearly clogged, the fuel filter, which was nearly clogged, checked/replaced all spark plugs, replaced exhaust O2 sensors, and maybe an oil pressure/level sensor. Still running rough. It seemed like a cylinder or 2 on the driver side isn't firing, but we know its getting spark. We switched the injectors from one side to the other and the misfire remained on the driver side, so the injectors themselves are operating, and 1/2 injectors on the driver side aren't receiving signal to spray.

About a week ago, we drove around with the scanner plugged in and compared oxygen sensor numbers from the driver and passenger side, and it appears that the driver side is running lean, so that backs up the injectors not spraying theory.

Sometime this week, we'll use a Noid light on the driver side to determine which aren't getting signal, then follow the wires to see if one is broken/shorted. If this isn't the solution, then I don't know where we go from here.

Any thoughts?
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Old 10-08-2018, 03:53 PM
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wes_wes101
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Also, here's a picture of it for yall see!
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Old 10-08-2018, 04:17 PM
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Since the miss fire stayed on the left bank, Yes look at the wiring. Also look at the fuel injector pigtails. Very weird that the whole left bank of injectors isn't firing. Were you able to read throttle position values with the scanner?
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Old 10-11-2018, 03:03 PM
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wes_wes101
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So it wasn't the whole left bank, just one or two. The noid light should clear up this whole "one or two or which one is it" issue. And I'm sure the scanner can read throttle position values, but I'm not aware of what they were. Is that something I should look into?

Last edited by wes_wes101; 10-11-2018 at 03:04 PM.
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