ive threw this up before but its really starting to pi$$ me off. i noticed today going by some other cars when i got on the gas the car makes a horrible metallic knocking sound i run 91 in it and it wont make the sound reving up in nuetral or in park and not that i know of cruising around but when jumping on it it makes that damn knocking sound. please help. i heard about a loose washer so where is it at? thanks

 

I'd get a scan tool and log some runs where the problem is so I could see what is happening. Knocking under load is bad.

 

i dont know when ill be able to get one but will any do what i need done? what could be causing the prob? its not a qiet engine and i was told it never would be and i dont use a drop of oil. any ideas you guys could throw out? thanks

 

How many miles are on the car? I think I may have the same problem...I was thinking it could be an exhaust leak or might be coming from the transmission or axle yolk*?

 

'Ello,

I just posted to another thread about the same issue. I bought a 98 z28 with 50k miles just a couple of weeks ago. I had the EXACT same problem--knocking when leaving a stop sign, and any time I'd hit the gas at low (<2500) rpm's.

The previous owner was using reg. gas, so I switched to Shell V-Power, then I had the car serviced at Chevy, which included service on the fuel injectors.

Sound is completely gone!

Now I have found an exhaust leak I need to fix...it's tiny, but the sound bugs me. <sigh> I'm going to go broke having a car I love so much!!!

 

man you might be my twin. i got a 98z 52,000 on it. ive been running exxon 91 i think ill change up and see what happens. what did they do to it when it was serviced? what your describing sounds identicle to mine. beautiful car but it sounds like crap.

 

Hi,

I sympathize...my beautiful new car and it sounded like a Model T sometimes...

Anyway, the previous owner said Chevy wouldn't even give the thing a tune up untill 100k miles, but I called and told them I just bought it and sometimes it ran rougher than I thought it should. I asked for lube, oil and filter (standard stuff), a peek at the tranny (reliability rating is below average for these cars--keep an eye on it), and to hook it up to the computer and make sure all was firing well.

They gave me a long list of 'schtuff' they did, and here's what I remember:

* Lube and oil
* Check and oil all linkages
* Service rear end
* Service tranny
* Service (and clean) fuel injectors
* Replace catalytic converter ($900 job for free-warranty by law)

My bill was $483.00 but the car runs great now. Oh yeah, be careful about the air filter--one thing I found is that they didn't even check my air filter! It had 1/2 inch of MUCK on it when I replaced it myself.

Another note: someone on another board told me that the computer in these cars can tell when the power just isn't there (bad gas, etc.) and will retard the timing to compensate. That is one good possibility for the knocking (not necessarily the gas, but something about how it's getting--or not getting--to the engine).

Hope this helps.

Say, got a pic of your new baby? I'd love to see it. If so, email me: hscotthooper@hotmail.com

 

LS series engines are more sensitive to carbon build up on the valves and pistons. Any good decarbon and/or injector service (preferably both) will help or maybe even get rid of it. Once you get it quiet - start using Top Tier fuels. They have more detergents than EPA minimum and should help prevent deposits. Not strong enough to remove but good to prevent. I'm a service advisor at a Chevy dealer and see this every day. About to have my 98 Z28 cleaned out too! If it still does it after a good chemical cleaning you may want to have it looked into further.

J

 

I had the same problem...

I spent about a month trying to diagnose the problem, but to no avail couldn't figure it out. Decided to take a look at the spark plugs and all 8 of 'em looked like this: http://www.mustangmods.com/data/5431/dsc01770.jpg

Changed the plugs out, and the car was running like a champ again.

My guess is thats your problem, cause it happened ot me at 53,000 miles.

Hope that helps ya,
-Dan

 

WE had the same problem. So we took it to the dealer cause its still under warranty. Anyways it turns out one of the connecting rods was broken, so they gave us another engine cause metal could of got into the engine and they didn't want to give us back an engine that could cause us problems down the rode. And there was only 1 month left on our warranty! And I though all dealerships were evil!

 

thanks alot for the help guys i feel beter now. scott i was searching forever and couldnt find anything similar and was ready to give up thanks alot what you had going on is exactly what is happening to me and ill throw you a pic soon. thanks guys

also sounds like a good time to change the plugs there such a pain i bet they havent been done, thanks dan

 

I'm glad to [try to] help.

As I said, I've seen posts on this issue around, and I've seen many, many different answers. Whatever the problem is, it's common. I suspect there are several things that can cause the knocking (gas, plugs, injectors, ...), so start with the cheapest and go from there.

Say, now that I know GM didn't even bother to check my air filter, I wonder if they even looked at the plugs??? The car runs great, but I want it to run its best! Sure wish I was mechanically inclined

 

mine makes a ticking noise at idle, i dont remember it doing it before the longtube install but i could have, i cant find a leak anywhere but when i pop the hood its not that loud but when you lay beside the y pipe it is loud.

 

Are you sure it was a broken connecting rod? Typifcally a broken rod will make the engine unuseable