More and more I'm hearing a lot of pinging in my 1998 Corvette's engine. The car presently has about 89,500 miles on it. Everything is pretty much stock with the exception of a Blackwing intake and Borla exhaust. I have always used Chevron 91 octane fuel (highest available in AZ) since buying the car a couple of years ago.

The pinging is fairly random as to when it occurs. Some days I won't hear it at all, and other days it will sound like the engine is going to blow apart. In general, the pinging is usually the worst under hard acceleration (maybe 3,000 or 4,000 RPMs and up) and, of course, when mashing the gas pedal in 5th or 6th gears.

I have researched countless threads on this issue. Here are just a handful of the possible causes that have been discussed (there are many, many more not listed here):

- fouled spark plugs
- defective spark plug wires
- dirty fuel filter
- carbon build-up
- dirty mass air flow sensor
- leak behind mass air flow sensor
- vacuum leaks
- faulty knock sensors
- faulty O2 sensors
- poor grounding on wires
- poor tune
- etc, etc, etc

I can safely say that my car's mass air flow sensor is clean, and there should be no air leaks behind it. The car also has new plugs and wires, and the fuel filter was recently changed as well.

Most threads point to carbon build-up as the issue. I've researched Sea Foam and how to use it in the intake, but I've also read a lot of horror stories on this product as well. I might be willing to run a can of it through the fuel tank, but I'd like to avoid dumping it in the engine. While carbon build-up could be suspect, I do enjoy running this particular Corvette quite hard multiple times a week (a lot of people argue that wide open throttle clears carbon as well as any snake oil product).

What I would really love is if someone local in Arizona who has a scanning or programming tool would be willing to take a drive with me after the Thanksgiving holiday. There are no codes being stored in my car's history, but I've read that such a device could pick up codes as they happen in real time. That certainly makes more sense to me than throwing money at random parts in hopes of fixing the issue.

Please provide whatever feedback you can. For anyone local in AZ, lunch (or ???) is on me if you are willing to take a ride to help pull codes on the car.

Thanks,
LO PHAT

 

Carbon.

I had the same pinging which progressed to a front knock sensor code. Changed the sensor and harness to no avail.

Seafoam and added a catch can. That worked for a year. Code and pinging came back.

Just pulled the heads and there's tons of carbon buildup on the pistons and chambers. You can scrape it off.

68k miles.

 

Can't believe you getting knocking and no codes. Are you sure it's not some other mecahincal problem? A lot or carbon buildup will cause this, maybe a seaform cloud is in order.

 

Thanks for the fast reply. I read some of your other posts on this as well. I do not want to turn this thread into a debate on the use of Sea Foam, but I am curious about something. After researching Sea Foam's website and talking with some mechanics, it sounds like repeated applications of using it only in the car's fuel will slowly eliminate any carbon build-up. Granted this method will take longer and cost more, but the theory seems pretty sound with fewer (if any) risks.

Thoughts on this are welcome as well...

LO PHAT

 

I'm wondering if Techron and Seafoam really works....

I used Seafoam once and it worked for a year.

I use Chevron or Shell gas, and add a bottle of Techron every so often.

I drive the car extremely hard, so I was shocked to see the amount of carbon.

Also, as a side note, I did another Seafoam treatment just 200 miles before removing the heads to find the carbon. It's hard packed, burnt into a shell of a mess that you really have to work at to scrape.

Have you about thought about upgrading your heads?

 

If your going to seafoam the engine MAKE SURE that you use the correct seafoam injection point. DO NOT use the brake booster vacuum hose!

Use the PCV vacuum port. Its at the FRONT of the intake manifold and will allow the seafoam to enter all of the cylinders evenly. If you use the brake booster vacuum line, the seafoam will all go into cylinders #7 & #8. That will not help you clean the rest of the cylinders

Attach a small hose to the PCV Vacuum port. Run the engine up to approx 2500-3000 RPM and allow the hose that you have attached to the PCV vacuum port suck the seafoam out of the can.

When approx 1/4 of the bottle is gone have your assistant who's controling the throttle, TURN OFF the ignition and shut the throttle. That will allow the seafoam to continue to be evenly sucked into the cylinders as the engine spins down and the seafoam will be in the RAW form that you need to disolve the carbon. When the engine is shut down, reconnect the PCV hose back to the manifold and allow the seafoam to sit over night.

As bad as you make you knock issue sound, you may need repeated treatments like you stated!

This has worked well for me in the past.

When you data log your engine check you LTFT and see if they indicate that your running RICH. If they are all significantly positive you may need to do some engine tuning to lean her out a bit.

Bill

Bill

 

Bill,

Are you saying that it could take repeated treatments adding Sea Foam directly in the intake manifold, or are you agreeing that it would take multiple treatments if I were to add it to the fuel tank only?

My wife and I will be putting quite a few miles on the Corvette this Thanksgiving, so I just picked up a can of Sea Foam. My thought was to add it to the fuel tank when I fill up as we leave. While I'm sure the effects on any carbon build-up will be slow doing it this way, is there any reason why I shouldn't dump the whole 1 oz can into the fuel tank?

Thanks,
LO PHAT

 

Unless your adding it into the intake, (IMHO) your not curing nothing. It will make your injectors and the back of your valves sparkling clean but, once that spark happens, its nothing more than fuel. Carbon is a tough nut to bust. I had to scrape it off more than once on old school V8's Theres not much SEAFOAM in a 14.7:1 air fuel mixture. I doubt that your going to see much of a difference.

Same thing as sucking an entire can thru the intake with the engine running. Its just FUEL and doesn't do much. RAW seafoam needs to sit in the cylinder to do anything to the carbon. Heck, ingesting straight WATER in through the intake does a wonderful job of carbon removal. Give that a try.

BC

 

guys.. especially stock tunes are super fat at WOT in many cases. so running at WOT isnt going to alleviate your carbon. in fact its probably adding to it.

i have been employed as a small engine tech in the past and carbon was the enemy so we always suggested WOT but those were conditions in air cooled engines where the heat would build up in the combustion chamber far mar.. enough to make a difference, and plus i had total control over the A/F with my screwdriver..

so, an idea i had. if you have access, get an open loop tune and go a hair past 14.7 at cruise for a while and see what happens. my buddy tunes cars locally and he has his car setup like that all the time for fuel economy.. but his engine is built pretty stout. im not recommending lean conditions for WOT, just cruise or high vacuum situations.

just sharing thoughts.

ive used seafoam.. i had a B headed 4V ford engine in which the accessory port clogged with carbon from not ever carrying fuel into the cylinder, only air. (two intake ports per cylinder, one accepted fuel from the injector, the other only carried air if the engine was revved past 3250, after which an intake motion runner control butterfly opened the the port was uncorked) motorcraft carb cleaner allowed to soak over night worked the best for removing the carbon in my experience. not sure how you'd manage that though with the engine assembled.

 

Plain old water is surprisingly effective at removing carbon. You speed up the idle a bit and mist it into the MAF or throttle body while running. It turns to steam in the combustion chamber and cleans like a *****. I've torn down engines with thousands of miles using water injection and was amazed at how clean the pistons/combustion chambers were. I'd certainly do an oil change shortly after using ANY method to dislodge carbon. Google it and see what you think. Good luck, Michael.