ENGINE

[AUTO DOCTOR PLUS]

I HAVE A 90 WITH 38,000 , I HAVE A MOTOR NOISE AT REV. WHEN LETTING OFF THROTTLE, SOUNDS LIKE BEARING NOISE?? OIL PRESSURE IS VERY GOOD, NOISE IS LOUDER IN MORNING, ANY IDEAS???/ HATE TO TEAR DOWN AND NOT FIND A PROBLEM, KEVIN

[jonszr1]

does the car make noise in neutral with the clutch out / you could be losing the flywheel?

[AUTO DOCTOR PLUS]

WE CHECKED THE FLYWHEEL IT IS OK, REV AND BACK OFF, IT WILL MAKE NOISE MOST OF THE TIME, WHEN PULLING OUT MAKES NOISE UNDER LOAD, KEVIN

[A26B]

You should try to locate the noise, front, rt side, left side, center, deep, etc and use a rod (wood dowel rod abt 2' long) placed on the engine and to your ear. Is the noise rpm frequency, no particular frequency, multiples of rpm frequency? Describe the noise; rattle, knock (heavy or light), tinny, etc.

Check all the pullys & belt to see if it's a bearing (tensioner, AC clutch, PS pmp, water pmp) or pully. A timing light works pretty good.

Very difficult to analyze like this.

[Kevin]

where in pa are you from

[AUTO DOCTOR PLUS]

I AM IN ALTOONA PA.

[Sgreg]

I had one of these weird noises under the car and almost tore the Z apart trying to find it only to discover it was a loose exhaust heat shield which really showed itself at 15-1800 RPM. Not saying this is what your problem is but sometimes little things can be the worst and lead to spending big money needlessly.

[A26B]

I'm wondering about the catalytic convertor(s). Wasn't it the 90 model without the screen and catalyst could get back into the exhaust header? Point is, it could be in the catalytic convertor, hence the reason to try & isolate where it's coming from and the frequency.

Loose heat shields, as stated above, have ocurred several times, driving the owners nuts to find the source.

[AUTO DOCTOR PLUS]

THANKS FOR THE POSTS, I WILL CHECK AND POST WHAT I FIND OUT, KEVIN

[Kevin]

I've been trying to think of anyone around the area that you could take the car to and I can't think of anyone. Sorry

[Peaven]

Loose heat shields, as stated above, have ocurred several times, driving the owners nuts to find the source.

:iamwithst I've been trying to locate mine for the last month that happens right at 1500rpm after the car has warmed up....I'm going to give it one more shot this weekend in an effort to finally kill this snake.:pray

[cuisinartvette]

Id second the motion on checking your cats and using a makeshift stethescope to piinpoint the noise. I had a 5.0 with cats that just "went bad" and could swear up and down I had a rod knock.

[jonszr1]

ronnie .< are you shure that wasn't brain knock from owning a FORD:mrgreen:

[RedSled]

My weird engine noise that fooled a few people turned out to be a water pump failing.

- Keith
'90 Red/Red #1383

[cuisinartvette]

ronnie .< are you shure that wasn't brain knock from owning a FORD:mrgreen:
Only Ford I had that gave me brain knock was the '85 that had a 460 on squeeze stuffed in it. :cool:

[jonszr1]

ok you got me oh great white ford knocker and your cup size is:mrgreen:

[tenedios]

THIS MAY HELP? I TAKE MY 1991 ZR1 TO STOCKER CHEVROLET IN STATE COLLEGE PA. THEY ARE THE SPONSORS OF USA-1 CORVETTE CLUB IN THE AREA WITH 90+ MEMBERS. THE MECHANIC THERE THAT SERVICES ALL OF THE CORVETTES IS MARTY SPECHT. HE IS ALSO A MEMBERSHIP OFFICER FOR THE CORVETTE CLUB. I HAVE FOUND HIM TO BE VERY KNOWLEDGEABLE AND AN EXCELLENT MECHANIC. THE PHONE NUMBER IS 814-238-4905 . I HOPE THIS HELPS.

[Kevin]

If you go to the dealer in state college let me know, I'll swing by and say hi and see if I can help

[Ccmano]

Some good ideas here... How bad is it immediately when you start the engine cold? There have been issues with timing chain tensioners on these engines. If one has failed completely you would get the noise you describe. Do the stethiscope test in the timing chain area on the valve covers, compare one side to the other.

Good luck,
Hans
:cheers: