Hello everyone, I’m looking for some advice in regards to my 2001 Corolla w/80k developing a considerably loud spark knock/engine pinging noise under acceleration. It throws no codes but pings like crazy and it never used to. It’s happened gradual over a long period of time. I’ve cleaned the throttle body and have done all regular tune up items with no improvement. It doesn’t ping at all on 93 octane, does some on 89 and terribly so on 87. Why is this? Does the 93 octane just act a a richer mixture of fuel to alleviate the ping? Should this sign point me in the direction that it’s definately a lean issue causing the pinging? Thanks for any help you may be able to provide.
Does the 93 octane just act a a richer mixture of fuel to alleviate the ping?
No, higher octane just makes the fuel more resistant to instant explosion, which pretty much IS pinging.
Should this sign point me in the direction that it’s definately a lean issue causing the pinging?
You may have an ignition timing problem, but it’ll probably take a pro to figure it out.
You likely have an EGR system problem. You need to examine the EGR passages and odds are you will find them completely or mostly plugged up with carbon deposits.
This needs to be resolved as severe and chronic pinging can ruin an engine.
It may be a lean operation problem, and that could be caused by low fuel pressure, a failing upstream oxygen sensor, or anything else that can cause a lean mixture. Lean mix means a hot cylinder, just as adding oxygen to a fireplace fire by blowing it in with a bellows causes the flame to become hotter.
However there’s another possibility I’d look at too, and that’s the EGR system. The Exhaust Gas Recirculation system prevents the cylinders from getting too hot by allowing a bit of inert exhaust gas from getting drawn into the intake and mixed with the air. It reduces the amount of oxygen per volume going in, in effect “cooling” the cylinders a bit to prevent pining and knocking.
Normally I’d expect a CEL with this, as well as with other conditions that cause preignition. Pinging and knocking are both fuel preigniting, pinging being a second flame front that forms and crashes into the spark-induced flame front, and knocking being the fuel igniting before the spark plug even comes into play.
Another thing you’ll want to look at is the antiknock system. It consists of a piezoelectric sensor mounted in the head that’s tuned to the frequency that a ping induces. This system should adjust the spark timing to compensate for pinging AND it should trigger a check engine light. It would appear that neither is happening right now.
As a matter of fact, since the pulses generated by the crystal both prevent pinging AND are the signal to the ECU that you HAVE pinging, I might start there first.
You have driven 80,000 miles in 14 or 15 years. That implies a lot of short trip driving. You may just have a lot of carbon buildup on top of the pistons raising compression and leaving hot spots, both of which cause pinging or pre-ignition. Try a dose of combustion chamber cleaner in your next couple of tankfuls and see if it helps.
If your Corolla is a standard shift, you could be driving in too high a gear and lugging the engine. This can also cause pinging, but unless you have changed your driving habits or moved to the hills it wouldn’t have just started.
I agree with ok4450 that the pinging is likely to be the result of a gunked-up EGR system.
When a friend of mine had severe pinging problems with his Corolla, and after other possible causes had been ruled-out, it turned out to be the EGR valve that was at fault.
Thank you all for your advice. I will begin to investigate these areas. First I will try some combustion chamber cleaner and then proceed to the Egr system and further.
Usually if there’s a problem with the EGR circuit, the O2 sensor, or the knock sensor it’ll cause the Check Engine light to come on.
If the Check Engine light isn’t on, then I agree with @oldtimer 11. There’s probably carbon deposits in the combustion chambers raising the compression of the cylinders causing the pinging.
The next time you fill the gas tank, add a can of SeaFoam http://seafoamsales.com/auto/ to the gas tank and then add the gas.
Drive the vehicle and see if the pinging diminishes.If it does, then the problem is with carbon deposits. So it may take more than one application of the SeaFoam to completely remove the carbon and stop the pinging.
“Usually if there’s a problem with the EGR circuit, …it’ll cause the Check Engine light to come on.”
I can tell you that the CEL was not lit-up on my friend’s Corolla, but after a thorough cleaning of the EGR, the pinging problem went away.
Your mileage may vary…
A 2001 Corolla doesn’t have an EGR valve. The problem is from carbon build-up or a failed knock sensor.
You’re right, Tester, but a CEL light should be triggered by repeated pinging as well. The device that lets the ECU know the problem exists is the knock sensor. That’s why I placed a bad knock sensor high on my list of possibilities. Not only should it prevent pinging, but it’s resultant pulses should be telling the ECU a problem exists.
They talked about Toyota syndrome on a couple of the shows. The engine would heat up and the carbon on the back of the valves would not allow the valves to seal. They recommended BG 44. I bought it off of Amazon. I used it on all 3 of my Toyos. It’s worth a try and the EGR is also VERY suspect.
Double check the spark plug gap hasn’t widened beyond spec.