Question about pinging at WOT and at higher RPM (4000 or more) only!

[Toronto_ACR]

I have noticed that my car will ping at WOT but only when it is at higher RPM such as 4000 or more. Can someone tell me what is causing this at only these conditions. Again it will not do it at WOT but at lower RPM, but only at WOT and higher RPM. Someone please get back.

Thanks

[Toronto_ACR]

Oh I forgot too add just in case someone needs the information to make an accurate assessment on what is causing the problem. The car is a 2002 ACR with a Mopar ECU and Mopar exhaust, and blue 10mm spark plug wires. Everything else is stock. Someone said that it is the O2 sensors, but correct me if I am wrong the O2 sensors dont work at WOT.

[FE 065]

Probably that ECU; an un-educated guess.

I've don't remember seeing a post where someone's had pinging on a mostly stock car..

Can you put the OEM ECU back on?

[99 R/T 10]

I bet your leaning out at higher RPM's, can't the Mopar be programmed to add fuel? Try putting back on the stocker and go for a drive!

[2BADD 4U]

bad gas ?

[utahviper]

Be careful. Sounds like you have detonation. Did this just start happening or has it been going on for a while? If it just started and you haven't made any changes then I think 2badd is correct, bad gas or low octane gas.

THis detonation can destroy your engine if it is not corrected. Also, if you go get new gas and it stops then great, if it doesn't then try changing the ecu.

[Tom, F&L GoR]

Knock would most likely occur at peak cylinder pressures, which is usually at peak engine torque. Beyond that engine speed, combustion pressures decrease, and knock tendency decreases. Hence, with NASCAR restrictor plate engines, drivers are instructed to only apply full throttle past a certain RPM. If you are experiencing knock past peak torque, then it does sound like running too lean (ECU, vacuum leak, fuel filter, fuel pump...)

[Jack B]

Tom, as usual, has good input. Here are a couple of easy items to check. Pull all the plugs and examine them under high magnification and look for splatter. The second item would to check fuel pressure. The Schrader valve is on the back/inside of the passenger fuel rail. The pressure should be 55 psi at all rpm's. The odds are, you will find it is the Mopar ECU. What octane gas are you using, bad gas is also a consideration.

[Toronto_ACR]

I appreciate all the posts. Increasing fuel pressure is an oild trick that i was using when I had my Buick grand national and I was blowing head gaskets like crazy with 30 ibs of boost. Jack does the shrader valve have a fuel pressure guage or do I have to install one myself.

I thought the main reason for going with a Mopar ECU was because it would add more fuel because it was calibrated for high performance racing. Can the Mopar ECU be reprpgrammed at all or is this not necessary. The problem with adding more fuel pressure is that it also adds more fuel at low speeds and engine idle. What about carbon on the pistons. Is that also a consideration

Thanks

[Marc Lublin]

These motors also have a tendency to build up carbon on the piston tops. Sometimes the carbon deposits produce hot spots which ignite fuel at the wrong time causing detonation. If you find this to be the problem, it can be fixed a couple of different ways.

[Vipermed 97,01]

More than likely your problem is your intake manifold gasket is defective.It is creating a lean condition.This mustbe addressed quickly as detonation can be detrimental at higher RPMs,especially with your year.Also if you have the Mopar performance PCM you have additional timming advance which is compounding the problem due to elevated cylinder pressures.Hope this helps

[Tom, F&L GoR]

How would an intake manifold leak affect full throttle? There is no/low vacuum and therefore little pressure differential to pull air through a leaky gasket. Unless the manifold is that significant of a flow restriction... (here comes the larger throttle body argument )

[Toronto_ACR]

If it is an intake gasket leak then your saying that the MAP sensor is not detecting WOT as the MAP is not allowing enough fuel to be put into the engine. Going back to another post, If it is a hot spot on the piston due to carbon buildup then how can that be fixed, and does anyone recommend changing the spark plugs. They presently have 3000 miles on them or is that a waste of money and time.

[Tom, F&L GoR]

Ummm, if it's a leak at the intake gasket, the MAP sensor wouldn't know at full throttle. It would signal zero manifold vacuum ("full" manifold pressure) with or without a leak.

Combustion chamber deposits can be mostly removed with brand name "fuel system cleaners" like the STP silver bottle, Techron. Make sure you get the fuel system cleaner, and make sure it sounds like it cleans everything. The difference between the 4 or 5 versions STP sells, for instance, is more dose rates than types of chemistry. And for combustion chambers, you need the highest dose.

[Marc Lublin]

GM makes something called top engine cleaner. You spray it in the throttle bodies and basically spray enough to try to stall out the car. 2 cans at one time works best. Then let it sit overnight and start it up (outside the garage) the next morning. All is supposed to burn off. I will smoke like crazy for a few minutes. I would change the oil afterwards (don't want some solvent mixed with the oil). I had this problem with my 94 & my 2000 and have spoken to several people with the same problem. I think the problem exists with many more cars out there, but just don't think some people know what they are hearing. Detonation in cars that are loud to begin with at high rpm's, is sometimes not so easy to hear. The other way to get rid of the carbon is to pull the heads and physically clean the piston tops.