Hello to all,

I bought a '94 coupe back in March w/93K miles on it and have been enjoying the heck out of it since. 1'st vette ever and I'll probably have one for the rest of my life....

1'st of all let me say how important this forum is and what I have learned thus far:

lesson #1: Purchase a FSM, I got one off e-bay. Invaluable!!

lesson #2: C4's run HOT. Scared the crap out of me the first time ambient temps warmed up and I got stuck in traffic. The forum relieved my worries and helped to understand how these cars operate.

lesson #3: Cruise Control didn't work. Though help of this forum determined brake switch needed adjusting.

lesson #4: Sport seats not functioning. Through help of this forum determined that, after a brake booster replacement which involves removing drivers seat, two cables beneath seat had been swapped.

lesson #5: DO NOT WASH THE MOTOR!!!! I've started cleaning it the hard way (simple green, brushes, rags, and carefully placed water and compressed air).

So, ......., just today I experienced a problem that I "think" has been covered on this forum, but I'm not exactly sure it has. Just wanted to run it by the masses as it may be familiar to someone here.....

Today was probably the hottest day so far in Atlanta. Outdoor ambient reading around 110 in the car. I made a 20 mile journey from work to my initial destination in modest interstate traffic (running around 70 mph) with several miles of mildly congested stop and go traffic. Water temp when I reached my destination was hovering around 228 to 230. Normal from all we know about C4's.

Left car in parking lot for about 20 minutes while taking care of my business. After that I cranked the car and it started idling really funny, sort of missing. When I put it in drive (automatic) and had foot on brake it tried to lunge forward on me and I noticed the tach jumping around. I continued home from there (about 5-6 miles) with the engine running poorly and seeming to miss. Higher rpms ran better but when I pressed the pedal for added power it wanted to hesitate.

Got home and checked codes (paper clip method, lesson #6). Found code H41. I opened hood to look for anything out of the ordinary (just in time to notice a heater hose that's swelling and needs replacing). Other than that hose didn't find anything. Went back inside house for a while (with hood open) to research the code. Returned about 30 minutes later, reset the codes and started her back up. Problem was gone. Took a quick drive and problem didn't return. Water temp was showing around 200 to 210.

The FSM suggests this may be the coil going bad (I think). Any help with this symptom would be greatly appreciated. By the way as far as I know my OPTI is the original. I'm in the process of deciding what to do about that with now 95K miles on the car. I don't have good maint. records on the car.

Thanks in advance for any help..

 

The FSM doesn't lie did you go through the flow chart for the DTC? Not sure if the ICM(usually code 42) could set this but they get flakey when hot and can cause some intermittant problems as wel as a good source of DOA if it dies while driving. You will know when the opti goes bad but I don't think this is it yet. My last 93 had the original opti in it at 140k.

 

Thanks much for the input. I didn't have time yesterday to go through the troubleshooting flow chart. Similar problem occurred this morning, where outdoor temps were below 80.

First occurrence was after having driven to parts store to order the water hose I need. Car was difficult to start when leaving the store. Once started the tach was jumping around and in gear the car tried to lunge on me (high idle with foot on brake). I drove it in to work and noticed that it only "seemed" to occur when the A/C was on. At a traffic light it began to idle funny and when I turned the A/C off it stopped. Turning A/C back on "sometimes" made problem return. I never experienced the problem with the A/C off. Also the engine did not seem to miss like it was doing yesterday. Checked codes upon arrival at work and only got C12. Made another stop along way to work and car started without problem.

For "peace of mind" I'm thinking of replacing (1) Opti (with MSD?), (2) water pump, (3) thermostat, (4) plugs and wires, and (5) possibly now the ICM. Any other suggestions would be appreciated. I would rather go "proactive" so as not to get stranded on a long trip.

 

A lot of us do not subscribe to the "throw money at it" troubleshooting method because at the end the problem may still be there.You have some strange symptoms and none of the parts you want to replace should cause what is happening. I don't disagree with changing out some of the things you list for peace of mind but not when you are having trouble and doing it in hope of solving it. You did not even list the coil which it could be. So what I am saying is solve the problem first before tossing all those parts at it you could end up worse or with multiple issues if you do.

 

The one thing about codes is that they are not dated. Who knows how long it has been in there. I would just check it a few times a week to see if it might return.

Seems like if you really had an actual open (code 41), the engine would probably not run. Just keep up with the code monitoring and hope it not the opti.

 

Readeasysport: I hear what you're saying. I do understand that shotgunning isn't the way to go. I probably just have two thought's going at the same time: (1) resolve problem and (2) perform some preventative maintenance. I definitely don't want to throw parts at the problem. That's more like going to the dealership.

I did inadvertantly leave the coil out of my list as well as the fuel filter. I'm attempting this afternoon to contact the previous owner to see if there are any residual maintenance records. The car belonged to her deceased husband, though she does seem to be well organized and may have "some" records. I'd hate to replace a water pump or anything else that has recently been done. I'll take your advice and focus on the problem at hand. The rest can wait till later.

pcolt94: Would be nice if codes were dated, I agree. After joining this group and before purchase of FSM I did check for trouble codes. There were no codes so this new code is "fairly" recent. I will continue to monitor for as long as any odd symptoms continue to exist.

Just went out to the car and moved it beneath the parking deck at work to get into the shade. No problems encountered, however the door chime which has never worked started announcing the key was in the ignition. I wish that would continue as that's already at the bottom of my problem list.

Thanks again for the replies!!

 

Those f%^&*$g door chimes do that. They are a pain and can be fixed but you have to pull the radio out to get to them. Mine does the same thing works sometimes and not at others. I have a replacement but am waiting till fall to fix it.Glad you took my advice one step at a time. Sometimes,unfortunately, it takes the car dying to find the source of intermittant problems. They suck too.

 

Problem for me is this is a daily driver and I don't like the idea of getting stranded anywhere anytime. I think I had better sign up for AAA, though do I really want them towing this car?

 

I have AAA and used it once. Just make sure if and when you call that the send a flatbed. I hear Ya on the stranded thing just go through the flow chart and do what it says. I bet a coil R&R is in your future (or worse).

 

Previous owner doesn't seem to have any maintenance records . Only thing she remembers are oil changes and the power booster for the brakes. She had mentioned that when I bought the car, which helped me in debugging the power seat and cruise problem. Apparently during this repair if you aren't careful those two items can accidentally get screwed up. Mine did (break pedal switch, sport seat wiring harnesses).

I must admit I didn't' really do any homework before buying this car. In fact wasn't really in the market for a car, especially a vette. It just happened. In hindsight I'm glad I have the car. It's soo much fun to drive .

So, getting ready to driver her home and see how she does.....

 

Number one error people make when diagnosing a problem is not checking the wiring. When you have a problem that comes and goes, it probably is a broken wire making intermittent or is barely connected.

 

To get at my chimes I have to remove the top pad. The chime box sits on top of the PKE attached by Velcro. I have heard that some people have removed it from the front but thought it was higher than the radio like behind the DIP, and cutting was required. Just seems like either way is a lot of work. But that’s not my main point.


I have repaired my chime box after buying the car. The chimes were intermittently working. When I got into it I hooked it up electrically and checked the chime signals with a scope. My investigation revealed that electronically all was working correctly right up the coil of the chime unit. It’s a strange device which is electro-magnetic. What I ended up finding is that the structure that holds the vibrating diaphragm required to be re-soldered with a large tip hot iron. This fixed it.

I can’t quite explain why this fixed it for I dis-assembled the entire chime assembly and could find nothing wrong and had the same problem. It was not till I re-soldered the metal structure that it was fixed. That was about 5 years ago and is still fine.

Hope this helps and explains some things for all.

 

Unhook the electric fan and see what happens. A few years ago my Camaro was acting in a similar way. Turned out the fan motor had a short in the windings. When the AC came on, the fan came on and the car ran bad. I figured it out when the fan went up in flames. Replaced the fan and the problem went away.

 

Drove her home, 20 miles in the heat, no problems. Drove to ball park for practice, no problems. Drove back home, no problems....... Used A/C the entire time. I'm beginning to suspect possibly the fuel filter? I have no idea how long the filter's been in there. Might as well go ahead and change it.

I'll take the advice of checking on the basic wiring and also operation of the fan. As far as I know they are both working though, especially since water temp is being well regulated in all this heat (90+ degrees) and humidity.

Thanks also for the tips on the chime. I plan to dive into that later on if it's not too much of a PITA.

I appreciate the feedback from you guys so far. It's really helpful

 

Drove in to dentist this morning, 2-0+ miles, no problems. Then on to work without idling issues.

If you look at page 50 of the 94 owners manual (https://www.mygmlink.com/pdf/go2cont...94corvette.pdf) there's a section on "Rough Idling". Do you suppose this was what was happening?