jimdhen

I have an 2002 C5 Coupe with 90k on it. For the last 30k miles this car pings when under strong acceleration at operating temperature. I have tried:

- Switching gas brands. Nothing works as well as BP 93 octane.
- Replaced the plugs. When the old plugs came out at 80k they looked pretty good.
- Replaced the wires.
- Decarbed.
- Taken to the dealer several times. No codes found and has latest software installed.

The only thing that makes this problem better is runnning Octane Boost in the fuel every tank. That's expensive and has to be hard on the combustion components like spark plugs.

Architect

Is your fuel pump up to par? Have you done any modifications? Any computer tuning?

Alex1217

Do you have any mods like an air intake. Sometimes, aftermarket air filters can cause lean conditions which the computer cannot compensate for.

RonVette2

Maybe time for a cutom tune, and try a few different tweaks while getting that done, and probably even squeeze out a few more horses... Just a thought.

jimdhen

I have not had any custom tuning done, and there is currently a stock air filter in. I removed the K&N filter that I had in there thinking that would help the problem. (It didn't). I have had it decarbed after I removed the K&N filter. The fuel pumps/senders seem to be fine. No issues. Had one replaced under warranty several years ago.

yellohvette

are ya sure it isn't just piston slap? mine does it a little bit as well - almost sounds like a slightly loose heatshield. i have had the car dynoed and it was definitely running rich, so I know it isn't ping...but most likely it is piston slap.

Of course, the fact that when you add octane boost, says that it might be running lean ... get it on a dyno and don't run it hard until then...i would spend 50-100 bucks and have them see what your AFR is...

good luck and hopefully it isn't pinging!

Snake Slayer

Sounds like your rear knock sensor is gone. I know there was a TSB for 98-02 model:

1998-2002: Service Bulletin: Audible Spark Knock (Detonation), MIL Illuminated, DTC P0332 Set
Subject: Audible Spark Knock (Detonation), MIL Illuminated, DTC P0332 Set (Replace Rear Bank Knock Sensor and RTV Area Around Sensor)
Source: Chevrolet Dealer Technical Service Bulletin
Number: 02-06-04-023

Models: 1998-2002 Chevrolet Camaro, Corvette, 1998-2002 Pontiac Firebird
with 5.7L Engine (VIN G -- RPO LS1)

yellohvette

That is interesting information, something to definitely consider! However, I don't think he was getting any codes at all from the DIC. Just get put it up on a dyno, let the engine warm up, and pull the car hard for 4 or 5 runs back to back, monitoring the AFR DURING EACH run.

You might also have a leak in the air intake system that is between the MAF and the cylinders. You might be getting some unmetered air in the system that is not being compensated for by the computer and thus running lean.

If you can't get it to a dyno, invest in a scan tool to monitor knock retard and see if you are infact experiencing knock.

Dirty Howie

So you are saying the knock sensor can be bad without a code and not retarding the timing thus allowing the audible ping???


DH

Humanoid 2.0

Over oiling a k&n can contaminate the mass air sensor wires, even if you remove it the contamination is still there. Did you clean your mass air sensor?

jovette

I agree, especially, since you've had the engine de-carbed.........sounds like your MAF may be dirty, clean it with the special MAF cleaner which can be purchased @ local auto parts store, just remove and spray the ____ out of it.

SR-71

My 2000 was the same way. Decarbed it, helped a little. Changed ignition stuff, nothing. Checked for intake leaks, couldnt find any. For my car if I used a can of concentrated fuel treatment it would cure the problem for about 3 or 4 months. Might give it a try.

Snake Slayer

My car would ping without any codes. I had the dealer replace the knock sensor under the TSB and that solved my problem.

jimdhen

All interesting information. I am headed back up to the dealer and check on the TSB issues. I know that hasn't been done. And wouldn't you think they'd check this stuff like a dirty MAF when you report the problem (nah?)

tblu92

what is the weather like there now--Hot Cool ?? if the IAT sensor is bad it could be keeping full timimg in when it is warm outside when it should be subtracting timing for the warm air temps

Jay-rod

Knock sensor for sure.Mine was the same exactly,changed the knock sensors(2).problem solved.Made way more power too.JER

excorvette

My 2000 ss has same problem and I have changed both knock sensors along with everything else recommended except tune. When the weather is cold no knock as soon as it's 70 plus it knocks at wot about 4000 rpm.
Car is very sensitive to gasoline and 91 is all that's available for me.
Just waiting to find a competent tuner as I suspect the car leans out.

jimdhen

Here is somewhat of an update:

- There have been some posts relative when the problem occurs. Warmer engine temps and warmer ambient temps definitely make the problem more pronounced, so let's say operating temps above 190 and outside temps above 60 degrees. Under a hard acceleration a noticeable rapid pinging, almost chattering, occurs at > 60 mph.

- Gas at 93 octane is most all I have ever used. When we had gas shortages here in Atlanta last year and I used some 87 octane it really pinged. I use BP/Amoco and when I don't, I get worse ping and erratic gas gauge readings (some previous board posts relative to sulphur explain this.)

- I had the car decarbed again after my previous post. Even removed the air induction and it was very clean before we even started. When that had no impact I went to the dealer and the service advisor and I went for a test drive. Duplicated the problem with him in the car.

- I am taking the car in Tuesday for the work to get underway.

Marlin

^
Update?


Having the same problem with my 2001. I am going to change the fuel filter soon. But everything else is in spec.

My dealer is a ***. The car is still under warrenty and they tried to say things were not covered. After 2 trips and calling the GM line it was fixed. So I don;t want to take it in, but the TSB listed does help (thanks).

VetteDrmr

1. The dealer won't clean the MAF; to him it's a non-serviceable item.
2. The cleanliness of the intake won't make a difference to the MAF; dust that makes it through the filter will slowly collect on the thermistors in the MAF, which insulates it from the airflow and causes it to "read" less air than is actually flowing. This causes the PCM to run lean.
3. If you have an air leak downstream of the MAF (like the bottom of the air bridge getting folded under where it connects to the throttle body), the engine will run lean.

Check these two areas before you run it back to the dealer. To clean the MAF, I hose down the thermistors (look just like small resistors exposed to the air) with electronics cleaner, then use a cotton swab soaked in cleaner to gently wipe them from the back side. Then hose them down again. Let everything air dry and reassemble.

HTH, and have a good one,
Mike