Maintenance

I've had my C4 for about a year now, but have not tried to fix any of the issues it has, until now. I'm looking for somewhere to take it, for all it's issues, in this area (Riverside, LA, Orange, or SD county, CA). Some of the issues I am having right now are:

YEAR: 1990
MODEL: coupe LT4
PROBLEMS:
- leaking oil (dealership told it was the oil pan and head gasket). It also looks like it might be coming from the transmision. not really sure.
- The car starts vibrating once I hit about 75 to 80 on the highway.

I guess I just need someone to look at it, and be able to perform the maintenance.

Any advice will help.

[c4c5specialist]

HI there,
Is this a LT5 or an L98??
Those are the 2 optional engines for 1990.
Vibration, is it felt through the steering wheel or the seat?
Does the vibration change when you take your foot off the gas pedal??
Allthebest, c4c5

Thanks for the reply. Yes it is a L98. The vibration is felt on the seat. The vibration does not change when i take my foot off the gas. Normally between 75 and 80 it vibrates, but once I go over 80, the vibration goes away. I plan to take it in for a tune up this weekend. Again, thank you for your reply, hopefully the it's not a big problem.

[c4c5specialist]

HI there,
A headgasket would have to be blown completely out for it to leak oil.
And you would be overheating to boot.
So, ignore the headgasket theory.

Valve cover gaskets are a known thing, as is the oil pressure sending units mounted under the distributor, for oil leaks.

Do you hear any squeaking as you leave from a stop sign?
IF so, you might have a binding universal joint.
Balancing all 4 tires is always a good maintenance practice.

Allthebest, c4c5

[ToolGuy]

I had a vibration at those speeds too only when appling the brakes. Thought it was the brakes but on the dyno last year the tech said you got a vibration from one of the rear tires. I had both checked for balance and it turned out to be the drivers side. It is in balance now and fine. I recommend like C4C5 said check your tires before throwing parts at the driveline.

[aquaholic]

i'de start with the tire ballance to. people drive these cars so little that it seems the tires get old, hard and out of round before they wear out. look at the date codes on them. if they're over 8 or 9 years old just dump em.

[leadfoot]

Even the lug nuts need to be checked and tightened from time to time or I get a vibration the car is so pure when all is right. Hope it is something simple like that pressure sensor Best of luck I wouldn't drive mine in that condition something going wrong at 80 isn't safe to ride imho

Thanks everyone. I needed new tires. The ones I had were pretty bad. It drives well now. I would of never thaught the tires affected the ride that much. Again thanks. Now I have to figure the leaking part.