Re: Rattle Underneath
 

You have been doing some research for sure!
Bet its nothign more than typical dual mass noise.
Bottom ends rarely fail in these.

Re: Rattle Underneath
 

From all that lm hearing lm relieved to think it is the dual mass for what ever reason it is, misfire,injector, dual mass itself....none of which is to herrendous to sort out.....

as said before l havent actually heard the car running yet ....lm going on what ive been told by the freind whos collected it for me. he is knowlegable on US classics in the UK but not the ZR1 in particular. That being said....he says it warms up fine, idles nicely apart from the noise described, good oil pressure, temperature good, doesnt smoke, no codes showing up.

l get home in a couple of weeks so will put the received opinions to test and get to the bottom of it.

Thanks to all :worship: and hope the originator of this thread accepts my thanks for having hijacked it

Dave Austin

Re: Rattle Underneath
 

Yes indeed,mine did the same thing when one injector died.If you didnt know about the fly wheel it would be very easy to assume the engine had a bad knock.

Re: Rattle Underneath
 

whats the method to test for and locate a bad injector...lm assuming that with the suggested DM relation we are talking primary injectors

Re: Rattle Underneath
 

I've only had my '94 for a short time, but after it's started, I hear a noise for a short time (5-10 seconds) that sounds like a can with a few dimes in it, being rattled. The seller was in China, and his sister was handling the transaction. When I heard it for the first time it kinda sounded a little like a rattling through-out bearing, but not exactly, so it had me worried. I noticed the noise went away almost immediatedly and never returned during the test drive. When I returned from the test drive I mentioned it to her and she said their mechanic said it was the cat(s), and that it was a common problem.

Thanks for the, rubber mallet, tip. I'm in the process of changing out my radiator...when I have some free time...so I'll already be under there, and tap them a few times.

The failing cat(s) brings up another question:

I thought the cat's were part of the emission system. If they were failing or already failed, wouldn't there be codes being generated? Mine is not displaying any codes. I remember seeing a post a long time ago about bypassing the cat's...or gutting them...but I can't remember if the post mentioned having to deal with computer related codes.

Re: Rattle Underneath
 

I didn't have any codes either. But when I had it at coreys for some other work I told him about the rattle. He didn't even know what it was. After he had cleaned and flow tested my injectors he put it on the dyno and as soon as he put his foot in it a big chunk of the drivers side cat blew out of the exhaust and hit the back bay door. He sold me a pair of manifolds with cats off a 90 Z he had lying around for $500. He said if he does the work I'm looking at about 14 hours of labor. He encouraged me to do it myself and said It wasn't rocket science but it was very labor intensive. So I did it myself and it took me 18 hours. There were loose chunks of cat material throughout the whole exhaust system so I had to take it apart and shake it out. But when I was done no more rattle. Good as new. My hands were cut up and swollen for three days after that. But like I said you only have to go through that hellish nightmare if you have a 90-92.:thumbsup: PS when I took the old manifolds off I could pick them up and shake them and hear the same sound that baffled me for monthes. And at that time people on this site were saying the same things about what the rattle could be. But nobody ever mentioned that it could be caused by the catylatic converters going bad. I am just tying to help out based on my own experiances owning this wonderful car. As is everybody else on this site. But somtimes the only way to tell whats wrong is when it finally blows up on you.

Re: Rattle Underneath
 

I just am not sure that I know "a definitive" way to check for one /and or multiple bad injectors. I would put a scanner on the motor and look to the fuel numbers. I would sniff the exhaust, as ya can smell a lean motor or at least I could smell the lean condition in my case when the injector coils failed. I would pull the plugs and read them with respect to what the left and right fuel numbers were saying from the scan. I would do an ohm test on the injector coils in cold and hot conditions. I would make sure to eliminate the ignition coils as being good and ohm the plug wires. You can ohm a pair of plug wires by doing the test on a "paired" set of wires and you also get to have a static ohm test on that ignition coil....ya know one plug wire end thru that coil to the other plug wire end.

Just as an aside when I had injector coil failure. There was a BIG miss as I had four coils fail all on one bank.....it was rather obvious in hind-sight what the root of my miss was but as a rookie Z owner I was lost. Those coil failures made my Z sound like a M/B 300 D...the plugs on that bank told me there was no gas, the exhaust smell from that bank's exhaust tips told me that bank was big time lean, the fuel numbers from the scan were what threw me for a loop. I had no experience with EEC at that point in time so I did not realize what those numbers were telling me. Oh, forgot this injector coil symptom. As the inj coils heat up the miss gets worse. On cold start the miss & lean exh smell was almost not there. As the motor got to normal coolant temp the miss & lean smell grew worse, as the inj coils heated up their shorts in their coils got worse cutting off more fuel.

If the injectors have an issue with the nozzels I would also look to the O2 readings and the cross counts(?) on the scan. I would expect to smell a rich condition at the exh tips and I would think that you would also see the rich condition at the plugs' electrodes. Ofcourse you also have to run down the ignition system for proper operation. Ofcourse if the nozzels are clogged then I would look to see that I smell that & see that at the exh and the spark plugs and on the scanner.

Sorry to be so long about this....I'm sure if I had a better understanding of EEC I could be more concise about this....the last car that I owned that I actually worked on had a holley 4bbl carb!

:cheers:
Tom

Re: Rattle Underneath
 

That was plenty Tom

ive got the '11 times only' datamaster scanning software.....will that work for me....lve never used it before.....lve never used scanners before:iamwithst
Other than that you were dead right of course....

use my eyes, nose, and a few simple electrical test tools....visual plug condition, smell, electrical test the injector coils, plug leads. coil packs

common sense if someone pokes you with it.

Cant thank all you guys enough.

For all that have helped. Im sorry lm not near enough to buy you all a drink.

Re: Rattle Underneath
 

:thumbsup:Dave!

That's why we are called The Brothers of The Beast!

Ya never know.....a pint a guinness & a wee bit o dram makes the world appear to be a more civilized place....we may cross paths and we'll raise that pint and have a good laugh!

:cheers:
Tom

forgot.....yes the datamaster would give the same data as a regular scanner, but I believe that it is more detailed as far as sampling data over time....I think. I've never used those software programs before so I'm not too clear on what all it exactly displays.