eddygig12

Hey Everyone. I recently purchased a 1990 C4 Convertible that was in running condition...bit of a rough ride, but not that bad. I just recently had a full Tune-Up, new TieRods, Tranny Flush, Power Steering Flush, Oil Change, New Valve Cover Gaskets, some new radiator hoses and a full Radiator Flush. To my surprise, there was only very, very little difference in the drive & performance. Of course I really need to take it on the highway and really give it some good driving (which I plan on doing weather permitting)...but I really was expecting a better ride after all the work I had done. I've spoken with some folks who came right out a said that the Vettes from the late 80's / early 90's were basically like driving a "bucket of bolts", a quote directly from a friend of friend. I would like to think that even though the car is almost 27 years old, it could run better. I plan on getting some shocks & new tires in the Spring. Again, I am a newbie with Vettes and have no problem admitting lots of ignorance about the cars...but do plan on learning as much as I can. I look forward to any commentary and advice.


Thanks, Ed

ctmccloskey

This is the place where guys who really "know" Corvettes help each other.
To get the best help you might list out which options your particular car has as this will help the experts identify the cause. The more info you provide about the car the easier it is for the others to help you. A good example of this would be "have the shocks ever been changed"?
I am relatively new to the Forum but have been a Corvette Owner for over 25 years. I have had tough questions answered quickly from sources and people I trust. I have learned volumes by simply reading about all the various problems people have had and their fixes. I have also been able to offer suggestions at times where my experience can benefit others.
You are most welcome here as we all have something cool in common, our love for Corvettes! Good Luck!

antfarmer2

Welcome to the forum. what is the date code on the tires?

billschroeder5842

Welcome to the Forum!

Couple of things... All the money you spent was largely on maintenance items. You did nothing for performance but you did logical stuff for dependability. Don't expect performance from maintenance.

Your friends are automotive nincompoops. The C4 is amazing squared away and a complete rush once you handle the basics. You are just getting started, so give yourself (and you car) some time to get antiquated.

So here is my advise:
1) get a FSM (field serve manual)
2) "Baseline" your car with maintenance and set performance to FACTORY SPECS
3) Then, Modify at will. Use the collective knowledge of the guys in CF (Corvette Forum) and you will go faster, cheaper.

Welcome to ThunderDome

bsstaats

What do you mean by rough ride? If you are talking about creaks squeaks and stiff handling then you're going to be chasing ghosts and throwing money at components that "soften" the ride only to see a loss of performance. So in that category all I can suggest is that you replace the shocks and maybe check to see the condition of the bushings. But if you are talking about rough engine performance then there is always a solution to that problem as when you get an l98 running properly there is no greater rush. If you can describe your problem I'm sure a lot of people will be able to chime in and help. I've had mine for almost a year now and when I got it every "common c4 issue" was an issue of mine and then some, since then I have replace almost every wear/fail item on the car. It will be a lot of work to get it where you want it but when you do, you won't regret your empty wallet.

eddygig12

Thanks all. I certainly will be more descriptive going forward. By rough ride I basically mean both Engine and Handling. I had the suspension checked and my mechanic (who also drove the car), said it really only need Shocks and a new set of tires and I do agree with him, but plan on eventually replacing more parts One of the posts mentioned something about a code on the tire? Where and how do I locate that? As for Actual engine performance, I guess I was expecting something more. Accelerating from a red light the car does not seem responsive. I have to really press on gas pedal just to get it going. The engine does have a very faint tapping sound (which I'm thinking could be a result of the car sitting). I am pretty sure the gas in the car (when I got it 3 weeks ago), was old. So I do plan on burning it off and filling with some good premium and good additives and injector cleaners. Gotta go now but will provide more info and progress. Anyway, I really do appreciate the replies and advice and look forward to more feedback. Again, excuse my ignorance on various things. Im more off a casual car enthusiast who only performs some work on my cars and relies and pay others for more extensive work. . (My other classic car is a 1968 Chrysler Newport Convertible).
Thanks again!

Ed

eddygig12

Thanks for the info. I did get an owners manua and a repair manual for 1984 to 1996 Vettes. I will look into the FSM and get it. Oh, by the way, the exhaust system has a new Catback that goes to just 1 old CC, which then just branches off into 2 pipes going to manifold. I eventually will replace that and feel that has something to do with the rough ride. I believe the factory specs call for 2, possibly 3 CCs? Mine just has that 1 in the center.

BrandensBeast

Welcome to the forum, if you want advice/information this is the place to be!

antfarmer2

Date code will be on the sidewall.

bsstaats

I doubt that your idle characteristics are from the exhaust system the O2 sensor (the sensor that tells your engine about what's going on with the exhaust) is before the catylitic converters. You can go back to factory if you want but if you will probably lose performance. I would suggest either leaving that or looking into aftermarket options/ going to a muffler shop to do it right and get some performance out of it (factory was a little overkill with 3 cats). As far as suspension the shocks and tires will make a huge difference but that is about all you can do. The rough idle can be a from a host of common l98 gremlins and I'll list them below. I won't go into detail but you can find all the information you need on this forum or googling your car and then the part (Corvette C4 TPS)

1) Throttle body. Go to the store and buy you a can of throttle body cleaner and get all of the carbon build up out of the butterfly and moving parts.

2) MAKE SURE YOURE RUNNING PREMIUM GAS

3) Clean Mass Airflow Sensor. Again go to the store and buy a can designed for that application.

4) TPS. The Throttle Position Sensor in these cars is held into its poison by two bolts it can loosen over time and begin to send an incorrect reading to the computer. There are several forums detailing how to check it and how to adjust it.

5) While messing with the TPS you should also set your minimum idle screw and your Idle Air Control valve (IAC) as they all work in tandem

6) Make sure the spark plugs are good and proper for your year (yes this is a real problem, you will soon learn there is nobody better at working on your car than you).

7) Check condition of spark plug wires

8) Replace in line fuel filter (under car by passenger side door frame)

9) This is a real problem, make sure your gas cap in screwed on properly (three clicks after tightening)

10) Replace o2 sensor
If none of these completely solve your problem then:

1) Check/replace MAF burn off relay
2 Check fuel pressure gauge, you can rent one at any autoparts store
3) Make sure some idiot didn't install the wrong fuel injectors (this happened to me)

Remember your vette is old and many of the sensors may need to be cleaned or replaced. And please change your oil as soon as possible you do not want to damage any internal components. I use Mobil 1 5W30

Your vette should not be sluggish. The l98 is know for low end and throwing you back against the seats. You may not have a lot of upper range power, but you should have low end torque for days.

Also the clicking can be a few things
1) Clicking fuel injector (normal)
2) Engine knock (not good, probably running hot)
3) Valve train/lifter problem (not good should have looked at)

Also, best of luck with your new project and empty wallet.

ddahlgren

Look under the console lid for the large label that should be glued to it. Write down all the codes as this is the option list for the car and should give a clue to what level of suspension firmness was spec'ed out. This will affect the ride a great deal.

2airtime2

I've only had mine ('92) a little over a month. These have a firm ride which gives them their road hugging ability. I'm still amazed every time I drive mine at how well it stays flat and handles curves. I've driven mine on the interstate for 3 trips of around 350 miles round trip and find the ride just fine on smooth roads. They don't soak up the bumps like dad's caddy but I can do 70mph on a curve he has to slow down to 45mph on.


Your engine should start, idle, and run as smoothly as any new car (mine does). These are fuel injected, computer controlled modern engines (even though they are 25+ yrs old). If yours doesn't post the specific issues and people here can help.

anesthes

It's a C4. It left the factory that way.

You are doomed.

Funny, my cousins '90 has a dead spot too leaving a light.

It's 26 years old. He put new injectors, fuel pump, distributor, etc in it then asked me to burn a chip for him. I told him the same thing I'll tell you, it's a tired 26 year old engine with almost 100k miles.

Low compression, weak valve springs, etc are typical. In addition to the junk injectors and electronic issues.

If you wanna spend a boat load of money, go through the entire car. Replace every bushing and wear item. Rebuild the engine, burn a chip for the new combo, etc.


-- Joe

FASTAZU

Welcome, I would try and get with some other owners in your area. Ride in a few other C4s take them for a ride. I would also look up the RPO codes as ddahlgren suggests.

http://www.corvetteactioncenter.com/...90/90prod.html

cv67

Sounds like you just need to spend time going over basics
COnvertibles usually got that 2.xx rear end ration not the best for acceleration. The TPS IAC deal etc may help you out.
One thing at at time. There are shocks that can soften things up a bit but in general the rides a little stiff.