I recently bought a 92 vette and am having a issue with the trans/clutch. when it first starts up it runs great, shifts good, burns rubber. but after I drive for about 20min. it wont rev past 3-4k RPM even when in neutral. I've changed the fluid about 5 times in a week. (first time it was really grimy). it drives great after I change the fluid even if hot. but with in 10min it goes to acting up again. im lost for what it is. weird thing is if I get outside the car and rev the motor by the throttle body it revs no problem. so any help I would appreciate it please!!!! really hoping I don't have to do a clutch swap

when its trying to rev up it like it starts to break up and just wont spin any higher. maybe something computer controlled? im so lost.

thanks!!!

 

These symptoms have nothing to do with your trans/clutch. It is an ignition or fuel related problem. First thing I would do is get a fuel pressure gauge on the rail and tape the meter to your windshield, go for a drive and record what your pressure is once you start experiencing the symptoms...

Have you ever changed the fuel filter? Is the opti original? Any damage to any of the plug wires, plugs, or coil?

 

Idk it's completely stock so I'm guessing so, Only owned it 2 weeks now. So I'll do a fuel filter and check the pressure and report back.

 

did the fuel filter. PITA but got it done and sealed up. went for a 20-30min drive and it drove great. parked it and went back out 20min later and started driving and it started doing the same thing again today. so seems to be heat related idk? tomorrow gonna get a fuel pressure gauge and check that. if that isn't it im guessing time for a opti, plug, wires, cap, etc. as far as I can tell its all orginal stuff.

 

Any other opinions? If it's electrical what's a good plug, wire, opti combo?

 

Well, I am the king of just replacing parts until the problem resolves itself, so idk why I am preaching about trouble shooting

But, I would still check the fuel pressure before you do anything else first. Could be the fuel pump, which can act erratic and also be heat related...

As far as a good plug wire, any respectable brand will do. AC Delco, Napa Belden, MSD, Mallory, Taylor. I run the Taylor 8mm Spiro Pro's. Great wire, but a real pain in the *** to remove the boots off the plugs...They're at Summit for around $50-$60 I believe. A good plug is the NGK V-power TR55 or stock AC Delco. I am a big fan of the Vpower, smoothed out my engine quite a bit...As far as opti goes I would try really hard to find an NOS unit, my second choice would be Delphi and/or AC Delco (DO NOT GET RE-MANUFACTURED). Chandler optis are cheap and are a hit or miss, I got 2 years out of one.

If you are up for just changing out parts to resolve the issue, change the coil and ICM first with original delco parts. You can get them at Rock Auto for a decent price. Make sure you use thermal grease on the backing plate of the ICM (You can get this at Radio Shack near the soldering supplies IIRC). Heat related engine dying symptoms usually point to a bad ICM. But, it can also be the opti...

Trouble shooting these things can be a real bastard...A good test for the opti is to drive the car up to about 20-30, shift into 5th and punch the gas. If it spudders and bucks, its the opti no question. This will also be a good test for your clutch to see how much meat is left on the friction disc. If it slips under load you don't have much longer...

Also might not hurt to throw a can of sea foam in the tank along with a fresh fill up of 93 non-ethanol.

Once you get these cars right, they can be very dependable and fun. Problem is not so much the car, but the age. Unless you do a bottom up resto, you will have to replace parts on a regular basis. Part of the car. Good thing is I enjoy wrenching, but I do get tired of electrical trouble shooting...

 

so which is it?

 

After the fuel filter it only brakes up at 4k above when it's really hot and been running awhile. Like it literally hits a wall. I just drove it today and it ran fine. Fuel pressure is 38-45 depending on rpm. I couldn't get it to act up agian but I didn't drive it very long either. It's got fresh 93 in it. The line isn't lol enough to tape the gauge to the wind shield while driving but I did let it get real hot and tested it. Pressure didn't have any weird drops. So next beat looks like electrical. Fml where's the icm located??

 

ICM on a 92 is right under the coil, attached to the pass side head on the front of the head and right behind the power steering pump resivor.

 

When it "hits a wall", what is the tachometer doing? Steady? Fluctuating/bouncing?

 

Tach is staying steady at whatever rpm it starts to break up at. It moves a little if I floor it and it starts to pop like it's trying to spin higher but just won't do it. Also how hot should my car run in traffic. Looks like it's at 230 or close to that.

 

230 is "normal" for these cars, one reason why they required full synthetic oil.

 

Have you checked for codes?