Made a vid of my "flywheel noise" , is it the flywheel? ---

[alwayscode390]

A couple owners ago told the owner before me that he changed the injectors. I have a receipt for the FORD yellow/red injectors and was given 15/16 black / silver stock injectors back ... and ONE spare yellow/red. I keep wondering if they reused a stock one and left out a Ford one?

The car stutters before the secondaries open up if I am not on the throttle atleast 1/3 of the way. I guess I could be having injector issues, but Haibeck mentioned in a post he hasn't seen any issues with the Ford replacement injectors.

The car also starts up in different crank time lengths. I thought it was the weather , but its been warm awhile. Sometimes it literally starts up in 1 second, sometimes it takes 3 seconds. It could be a leaky injector?

The car runs great though , put out a solid few runs on the Dyno with zero issues.

If it was an injector, how would that make the rattle sound from the back of the engine?

If it was a single mass flywheel ... is it easily detected with the car in the air?

I am at the point where I would hate to replace the injectors and spend $1k on parts I don't need ... or same with the clutch/flywheel.

I guess if I replace them I know whats in the car, but I don't exactly have $2k to throw at parts at this moment.

I actually planned to take the car down the 1/4 mile on Wed next week ... should I scratch that idea until I figure out whats going on?

Thanks guys , I know its hard to diagnose through the computer but I don't know anyone local with a ZR-1 to compare the car to , especially not a LPE topend car. I also know my car will have quirks that the stock ZR-1s wont have.

That vid I posted was mainly a test vid to see if I could even hear the issue , I will try and get a better one to post soon!!! ---

[Kevin]

are you going to the gathering? spend a $1000 there and i'm sure someone will be able to help you

[alwayscode390]

No I cant make it.

That actually reminded me that the previous owner told me he took it to Bowling Green 2 years ago. Drove it all the way there and back for a ZR-1 / Corvette gathering.

People there said the car seemed solid and had no issues. He keeps telling me its the dual mass , and they are louder on cam timed cars because of the lope at idle.

What he says makes sense.

I was just wanting to make sure before I blew something up on the track, so I made the vid to ask you guys for a 2nd opinion. ---

[Schrade]

Sounds too 'light' to be flywheel, although it does sound like something in a 'chamber' of a sort with resonance - perhaps inside bellhousing ... exhaust rattling against something ...

Need a scan, to see if the knock sensor is picking it up. I HAVE seen KS pick up tranny / clutch issues in B-body...

[alwayscode390]

I really need to fix my laptop and run a scan. I bought Datamaster for the car a couple months ago.

I will get on that, now that the weather is nice again.

I took pics of under the car , I didn't notice the exhaust hitting anything ... but its possible.

I heard the dual mass flywheels can get worn out , or broken ... could that be a possibility too?

Car put down 402rwhp with a broken middle resonator rattling away (which has since been fixed with an x-pipe)

The screwed up thing is nobody has even mentioned the sound to me, not even my mechanic ... and the car has been in there for multiple things recently.

Thanks ---

[QB93Z]

I have a Lingenfelter 368 cuin 1990 ZR-1. I had a noise similar to what you recorded (but not as loud) that made me think it might be a bad lifter or valve.

I had Marc Haibeck listen to the car a BG and he diagnosed (correctly) that the noise was from a torn rubber fitting and a bad check valve in the Air System. I fixed the problem my self.

The Air System is a pump the injects air in to each exhaust runner during the first few minutes of engine operation. It is an emissions related system that helps the Cats get up to temperature quickly.

The system has pipes, Tees, fittings, and check valves that run from the area forward of the left front wheel and runs to the left side exhaust piping, and crosses under the engine to the right side exhaust piping. The fittings and check valves, if they were not removed, should be visible just below the cam cover (easier to see on the left side).

On my engine, there was a rubber tee on the right side that was twisted and split. This allowed the Air check valve to click shut on each exhaust cycle for that cylinder.

Some cars with headers still have the Air system attached to small pipes welded to each runner of the header. (Mine did after Lingenfelter worked on it.)

On a separate issue, I have heard many ZR-1's that have flywheel noise that goes away when the injectors are replaced. It is a common occurance. I am not saying that this is definetly your problem, but it might be worth investigating. There is a procedure to measure the coil resistance of each injector, which may help diagnose an abnormal or failing injector.

You mentioned that you car starts in one second sometimes and 2-3 seconds other times. I consider this normal. The ignition system needs to detect the crack position signal before it will start firing plugs. Start time, therefore, depends on how far the engine has to rotate before the crank position slot passes the detector.

Good luck.

Jim

[alwayscode390]

Looks like I have a little investigating to do under the hood.

Sounds like the Air System may be the culprit.

Would it throw a code for the Air System or not necessarily?

I don't have cats installed currently, LPE took them out when they installed the Borla Exhaust ... maybe they tuned out the emissions stuff then?

Next I will try to see if my mechanic can tell what flywheel is installed, and ohm out the injectors.

Thanks! ---

[WVZR-1]

If you're going to have it checked by your mechanic I would think that if it was "airborne" and running a stethoscope would pinpoint the source/location of the noise. An inexpensive automotive stethoscope is sometimes a very valuable diagnostic tool.

[QB93Z]

The Air System does not throw a code if it is removed.

There is no tuning aspect to the Air System that I know of. Nothing has to be done to the ECM or the tune when the system is removed.

If the Air system is installed, you will have to cap (plug) the connection tubes to the headers to remove the system.

There is an excellent write-up on Marc Haibeck's website about measuring injector coil resistance. CAUTION: the procedure requires disconnecting the plugs to the ECM and probing the connector terminals. I would make sure that the mechanic doing this understands all of the precautions for working on electronic equipment.

Jim

[RyanChappel]

flywheel trying to compensate for bad injectors....Marc replaced the injectors with Accel units and the noise went bye-bye..