Questions from a ZR-1 newbie - ZR-1 Net Registry Forums

SharkPilot · 04-24-2006

Now that the finances are pretty much ready, I am beginning a search for my first ZR-1. A friend and I test drove one at a local Corvette dealer yesterday and I have a couple of questions.

First, some info about the car:
It's a 1992 model (#302) with 24,000 miles. The car looks really nice with nice black paint and almost no wear showing in the interior. The engine's finish looks good and it is clean (doesn't mean a whole lot, I know). The idle was real smooth and the car drove nicely. No check engine light only a "Low Tire Pres." light was on.

1. Sitting in the car with the engine idling, there was a light knocking sound coming from the engine/clutch/trans area. It was not loud, just noticeable and it varied with engine speed. While driving it was only heard at idle and low engine RPM.
Is that just the dual-mass flywheel or could there be something else going on?

This is the first ZR-1 I have driven and have only riden in one before this so I don't really know what to expect soundwise. All of my Corvette experience is with my Sharks and a couple of C5's.

The vacuum pump only ran for a few seconds before the engine started so from what I have read that is a good thing. Is there any way to verify that the secondaries are actually opening or do you just have to drive it, key 'off' and key 'on', and let the seat of your pants tell you? We only went a couple of miles and I didn't get it above 4000 RPM.

This is getting long so I will stop here. Many thanks in advance for anyone that can give my any advice or pointers.

SharkPilot :steering:

tomtom72 · 04-24-2006

Hi Sharkpilot & welcome to this particular corner of the passion!!

Power Q: If the power key is on you can feel the difference in power level as the motor passes 3K rpm. There is an obvious difference between "key on" & "key off" even at that rpm limit, even without mashing the gas...you can feel the 2* injectors calling your right foot!

Dual mass flywheel Q: The D/M fly wheel is most noticable at idle, zf in neutral, it kind of "knocks" a bit. As you move the car in 1st or 2nd you also hear some "gear clash" noise like the old M22's as the zf has straight cut gears. It's a bit noisy & the fluid condition could help quiet or magnify the noise. If you "lug" the motor down low you could get some noise from the D/M flywheel. I'm only an apprentice owner, 12/04, so I can only say that I think what you hear is normal. I changed out the GM trans fluid to the BMW stuff & it made the trans quieter. The persistant "knock" could be that the fly wheel is having weight damper issues...I'm not sure but past a certain rpm in my car the knock disappears entirely & only the gear noise in 1st & 2nd is audible. I'm gonna defer to the more senior members to elaborate.

LTPWS light: The light will show if the system fails it's self diagnostic check, all the sensors have to check in w/the reciever. Or if the wheel sensors are not all there the light will be on. Or if the car was not moved past 4 mph a few times you will get the light(in my 90) and it will not go off till a restart is made and the system has time to go thru a complete self-check. Good news is that GM still has your style sensors, they were changed in 92 I think.

No leaks in the secondary vac system if pump primes the sys & then stays quiet for long periods of time without the motor running. Great!

Sorry to be so long winded! Congrats on coming to join us! Be suspicious & check with a code reader on the ALDL port or run the VIN at a local chevy dealer to get a warr/recall history on the car, but you know all that. The car sounds good, good luck in your quest.

Tom

Z Factor · 04-24-2006

Glad you are seriously looking to buy a KOTH.

A clean engine bay shows that the owner has put extra care into it, so that is always a plus in my book. As to the low pressure light, it could be as simple as adding air to the tires.

The sensor could be bad as well, but again, not a huge issue. The noise/knocking you are hearing could be several things. Our ZF trannys are a little noisy, but not that noticeable. Is it possible that the flywheel has been changed to a aftermarket one? If so, expect it to sound pretty loud compared to a stock dual mass. It could also be a bearing, but it might just be the normal sound and you are not use to it. If it is very loud, have it checked out first. The fact that the pump cycled off is good, but keep the key on with the motor not running for a minute to see how long it takes to cycle on again. If it re-cycles on too often you have a leak, otherwise you are fine.

BTW- Get her up past 4000rpm if you can safely do so and see how she performs.

04-24-2006	#1
SharkPilot Join Date: Aug 2005 Location: Anaheim, California Posts: 105	Questions from a ZR-1 newbie Now that the finances are pretty much ready, I am beginning a search for my first ZR-1. A friend and I test drove one at a local Corvette dealer yesterday and I have a couple of questions. First, some info about the car: It's a 1992 model (#302) with 24,000 miles. The car looks really nice with nice black paint and almost no wear showing in the interior. The engine's finish looks good and it is clean (doesn't mean a whole lot, I know). The idle was real smooth and the car drove nicely. No check engine light only a "Low Tire Pres." light was on. 1. Sitting in the car with the engine idling, there was a light knocking sound coming from the engine/clutch/trans area. It was not loud, just noticeable and it varied with engine speed. While driving it was only heard at idle and low engine RPM. Is that just the dual-mass flywheel or could there be something else going on? This is the first ZR-1 I have driven and have only riden in one before this so I don't really know what to expect soundwise. All of my Corvette experience is with my Sharks and a couple of C5's. The vacuum pump only ran for a few seconds before the engine started so from what I have read that is a good thing. Is there any way to verify that the secondaries are actually opening or do you just have to drive it, key 'off' and key 'on', and let the seat of your pants tell you? We only went a couple of miles and I didn't get it above 4000 RPM. This is getting long so I will stop here. Many thanks in advance for anyone that can give my any advice or pointers. SharkPilot :steering:

04-24-2006	#2
tomtom72 Join Date: Dec 2004 Location: Jacksonville, FL USA Posts: 4,645	Re: Questions from a ZR-1 newbie Hi Sharkpilot & welcome to this particular corner of the passion!! Power Q: If the power key is on you can feel the difference in power level as the motor passes 3K rpm. There is an obvious difference between "key on" & "key off" even at that rpm limit, even without mashing the gas...you can feel the 2* injectors calling your right foot! Dual mass flywheel Q: The D/M fly wheel is most noticable at idle, zf in neutral, it kind of "knocks" a bit. As you move the car in 1st or 2nd you also hear some "gear clash" noise like the old M22's as the zf has straight cut gears. It's a bit noisy & the fluid condition could help quiet or magnify the noise. If you "lug" the motor down low you could get some noise from the D/M flywheel. I'm only an apprentice owner, 12/04, so I can only say that I think what you hear is normal. I changed out the GM trans fluid to the BMW stuff & it made the trans quieter. The persistant "knock" could be that the fly wheel is having weight damper issues...I'm not sure but past a certain rpm in my car the knock disappears entirely & only the gear noise in 1st & 2nd is audible. I'm gonna defer to the more senior members to elaborate. LTPWS light: The light will show if the system fails it's self diagnostic check, all the sensors have to check in w/the reciever. Or if the wheel sensors are not all there the light will be on. Or if the car was not moved past 4 mph a few times you will get the light(in my 90) and it will not go off till a restart is made and the system has time to go thru a complete self-check. Good news is that GM still has your style sensors, they were changed in 92 I think. No leaks in the secondary vac system if pump primes the sys & then stays quiet for long periods of time without the motor running. Great! Sorry to be so long winded! Congrats on coming to join us! Be suspicious & check with a code reader on the ALDL port or run the VIN at a local chevy dealer to get a warr/recall history on the car, but you know all that. The car sounds good, good luck in your quest. Tom __________________ 1990 ZR-1, Black/grey, #2233, stock. ZR-1 Net Reg Founding Member #316 & NCM member

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04-24-2006	#3
Z Factor Join Date: Dec 2003 Location: S. Florida Posts: 2,667	Re: Questions from a ZR-1 newbie Glad you are seriously looking to buy a KOTH. A clean engine bay shows that the owner has put extra care into it, so that is always a plus in my book. As to the low pressure light, it could be as simple as adding air to the tires. The sensor could be bad as well, but again, not a huge issue. The noise/knocking you are hearing could be several things. Our ZF trannys are a little noisy, but not that noticeable. Is it possible that the flywheel has been changed to a aftermarket one? If so, expect it to sound pretty loud compared to a stock dual mass. It could also be a bearing, but it might just be the normal sound and you are not use to it. If it is very loud, have it checked out first. The fact that the pump cycled off is good, but keep the key on with the motor not running for a minute to see how long it takes to cycle on again. If it re-cycles on too often you have a leak, otherwise you are fine. BTW- Get her up past 4000rpm if you can safely do so and see how she performs.