1989 Corvette Needs EXERCIST!! Part 2 / Who's got the answer? Who's the man?

[Justin B.]

O.K. , Here's what the 89' is doing: It cranks right up and does exactly what they should all do. With the car in park, you mash the accelerator pedal up to 2000 rpm and thats about all the engine will put out. If you want to know what it sounds like then imagine this: An 89' Corvette doing 20 mph up a steep incline in overdrive! Then once I get off of the accelerator pedal, the rpm's drop so low to where it would probably cut off if I didn't fight to keep it running with the foot pedal (like you would do with a cold natured carburetor). I THINK that it may smell a little rich. Anyway, I had the battery and altenator checked and they both tested "very good." I just replaced the E.C.M., no help there. I just replaced the M.A.F. sensor, no improvement. Just out of desperation I replaced the spark plugs, fuel pump, fuel pump relay, and fuel filter, nothing. So, after spending BIG money on a car that not worth big money, what do I do next? I want to fix it because it is fun to drive and it only has 67k miles but I could be putting this money into my 58' or somewhere else. I can't sell the car like this because I would basically have to give it away. And, its a challange which is driving me nuts and I can't seem to walk away!

[Joel A.]

Re: 1989 Corvette Needs EXERCIST!! Part 2 / Who's got the answer? Who's the man?

Are there any codes stored in the ECM? My first idea is it sounds like the catylitic converter(s) is stopped up... Need to try to get some codes out of it to see what direstion to go in.

[John S.]

Re: 1989 Corvette Needs EXERCIST!! Part 2 / Who's got the answer? Who's the man?

I agree. Worked on a non corvette afew years back with similar symptoms. Did not have a clue to the problem until I walked by the exhaust pipe of the car with shorts on and felt no exhaust. Removed cat and punched out insides with a rod or poker of some sort. Put the empty housing back on and car ran perfect. Check your exhaust while some one is on the gas and see.

[George D.]

Re: 1989 Corvette Needs EXERCIST!! Part 2 / Who's got the answer? Who's the man?

I had a similar situation with my 90. Turned out to be the engine temp sending sensor which sends sigianl for the fuel injection cold start. I didn't have a code initially, but finally it threw a code. Easy and inexpensive fix.

Good Luck

[Paul J.]

Re: 1989 Corvette Needs EXERCIST!! Part 2 / Who's got the answer? Who's the man?

Justin, GM used two other emission related parts in 1989 on thier engines. Some of the symptoms which you describe are indicative of a bad Throttle Position Sensor. TPS's were used on throttle body and other injection systems, and there is a very good chance that this is your problem. TPS's are readily available for around $70 retail. Another device that I've had problems with is the Idle Air Control valve. Take it out and clean the pintel and the seat, then put is back and try it. You can buy these new for $114 retail. These parts seldom go bad, but when they do they are a pain to diagnose, but very easy to replace. There is also probably some information on the internet about testing these, which you should do first.

However, before you do anything with these take the weatherpak connectors loose and make sure everything is dry.

Paul

[Terry M.]

Re: 1989 Corvette Needs EXERCIST!! Part 2 / Who's got the answer? Who's the man?

However, before you do anything with these take the weatherpak connectors loose and make sure everything is dry.

Paul

And not corroded. The weatherpacks are great at keeping water out, but once it gets in they are not so good at drying out. end result is corrosion and poor contact.

[Larry M.]

Re: 1989 Corvette Needs EXERCIST!! Part 2 / Who's got the answer? Who's the man?

Justin:


If all else fails, and no one here can help solve your problem, then check out this website: https://corvettetroubleshooting.com/...eshooting.aspx

Gordon should be able to assist, although the advice may cost $$.

Larry

[Justin B.]

Re: 1989 Corvette Needs EXERCIST!! Part 2 / Who's got the answer? Who's the man?

Thanks to everyone! I'll head back out and start beating and banging. I will follow-up and maybe we can put an end to this madness.

[William C.]

Re: 1989 Corvette Needs EXERCIST!! Part 2 / Who's got the answer? Who's the man?

Don't forget to check the coil in the distributor. I had mine die on the road once, engine would start, but not run under a load. I believe there was a defect in the originals and the replacement unit was improved. As I recall, the '89 had a "hotter" coil and it caused some problems.

[Peter M.]

Re: 1989 Corvette Needs EXERCIST!! Part 2 / Who's got the answer? Who's the man?

Are there any codes stored in the ECM? My first idea is it sounds like the catylitic converter(s) is stopped up... Need to try to get some codes out of it to see what direstion to go in.

Joel is right. The first place to start is the ECM codes. These cars are pretty easy to diagnose, but you have to pull the codes and see what the onboard diagnostic system is telling you. It will be very expensive and quite frustrating to just throw parts at a C4. You can purchase an OBDI connector for your laptop computer for about $65. The WINADI or TUNER PRO diagnostic software is free on the Internet. Finally, you really need to invest in a GM Shop Manual for your car. You can't really work on these cars without the diagnostic software and the Shop Manual. After that, its actually pretty easy and inexpensive to keep these guys running.

[Edward J.]

Re: 1989 Corvette Needs EXERCIST!! Part 2 / Who's got the answer? Who's the man?

Justin, Some advice is before just replacing the convertor- just unbolt the front pipes and take for a spin with the pipe hanging. this should give you a idea if it is pluged. May be a little nosiey. Also sometimes the more the engine runs the heat tends to swell up the internals of the convertor and choke the engine.

[Patrick H.]

Re: 1989 Corvette Needs EXERCIST!! Part 2 / Who's got the answer? Who's the man?

Justin, Some advice is before just replacing the convertor- just unbolt the front pipes and take for a spin with the pipe hanging. this should give you a idea if it is pluged. May be a little nosiey. Also sometimes the more the engine runs the heat tends to swell up the internals of the convertor and choke the engine.

Let's not forget his original thread - this all started because the engine got wet.
I'm betting the converter is in no way involved in this.

[Edward J.]

Re: 1989 Corvette Needs EXERCIST!! Part 2 / Who's got the answer? Who's the man?

Let's not forget his original thread - this all started because the engine got wet.
I'm betting the converter is in no way involved in this.

Pat, I did not know this was posted prev. if the engine got wet anything is possible. underside of Distributor cap moisture? generally it will misfire and backfire on accel. Strike the convertor.A scan tool would make life a lot easier with driveability problems. guessing it a expensive way to do things with computer controlled cars.

[Justin B.]

Re: 1989 Corvette Needs EXERCIST!! Part 2 / Who's got the answer? Who's the man?

And the demon has been destroyed, executed, and chased away by the higher powers of the NCRS technical discussion board participants. The catalytic converter was extremely clogged up! The poor 89' couldn't breathe. The mighty demon would let it breathe but not exhale!
Oh well, the car now has a new computer, mass air flow sensor, plugs, fuel pump, and fuel filter and, I have less hair. Thanks fellows for your help! Justin

[Patrick H.]

Re: 1989 Corvette Needs EXERCIST!! Part 2 / Who's got the answer? Who's the man?

And the demon has been destroyed, executed, and chased away by the higher powers of the NCRS technical discussion board participants. The catalytic converter was extremely clogged up! The poor 89' couldn't breathe. The mighty demon would let it breathe but not exhale!
Oh well, the car now has a new computer, mass air flow sensor, plugs, fuel pump, and fuel filter and, I have less hair. Thanks fellows for your help! Justin

So the next natural question is...
How poorly did it run before the motor got wet?!?