CarTalk.com Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

Computer profiling

I have a '99 ford escort, 2L SOHC engine, 152,000 miles. It’s been taking to pinging/detonation under load, and a mechanic told me to ask the Ford people to “recalibrate” the computer. I think he actually meant to re profile the computer. I understand that, removing the battery cable and reinstalling it will set the computer up for a new profile, generated in a few miles of driving. I did that and the pinging/detonation s became milder, but did not disappear.



There was also a code show up indicating that the oxygen sensors were not in sync, apparently. So will that affect pinging/detonation?



Another person behind the counter of a parts shop said removing the cable does nothing to engine performance, but I did notice a difference.



The plugs were changed at 120,000 and other maintenance work performed.



Finally, can plugs of a lower heat range be substituted for the ones in the engine now?

Ping/detonation not the same,“google” each.

Post 02 sensor codes,yes this issue needs to be resolved.

Battey cable will not “restore” performance.

Pull plugs and read them (compare to chart)

I will look if there is a PCM “reflash”.

No “reflash” or mention of ping in TSB’s

Do not substitute plugs. Fix the cause of the problem instead. Going to the incorrect heat range of plugs can have unintended and undesirable consequences.

You’re on the right track, however. Pinging is generally considered a secondary wavefront self-forming and crashing into the spark-induced wavefront because the cylinders are too hot. Preignition is generaly considered to be the cylinders firing before the spark plug, also a manifestation of hot cylinders.

Cylinders can get too hot because of a too-lean mix, like using a bellows in a fireplace…it burns hotter with more oxygen applied. Oxygens sensors can definitely cause this. Your engine is an inline 4-cylinder engine, so you have one sensor before the catalytic converter and one after. The one after monitors the performance of the converter. The before one is the one that provides an input to adjust your fuel mix. I’d want to see the signal from the one before (known as the “upstream” sensor).

You also have an Exhaust Gas Recirculation (EGR) system that should allow a bit of inert exhaust gas to mox with the air being drawn into the engine when under load. That keeps the cylinders from becoming too hot, the source of pinging. These can and do get clogged up with carbon, especially on older engines that are burning some oil, because they pass exhaust gasses.

You should also have a “knock sensor” that should be functioning. While its capabilities to adjust for pinging are limited, it’s a piezoelectroc (or piezoresistive) accelerometer that’s “tuned” to the frequency your engine makes when it pings or (ignition) knocks. That should have tripped a fault code due to recurrant pinging.

Advanced ignition timing can also cause your symptoms, but this is not what i’d suspect first.

Summary: get the signal from the oxygen sensor checked and if it’s bad get the bad oxygen sensor replaced. Have the EGR valve cleaned. I’d also want to check to see that the knock sensor was good…and no, contrary to popular belief it cannot be checked by just banging on the head. It’s a tuned device.

And find a new shop.

You might have a bad knock sensor if an Escort comes with one. The EGR system might be stuck. Oxygen sensors won’t cause pinging or preignition. Is the timing belt getting old?

All automotive engines rely on detonation. If the fuel didn’t detonate, you wouldn’t go anywhere. “Pinging” often refers to premature detonation, which is what happens when the fuel is detonated by the compression of the cylinder before the spark plug has a chance to fire. It has multiple possible causes. Some possible causes are:

-The combustion chamber might be too hot.
-The octane of your fuel could be too low.
-Your EGR valve could be malfunctioning, if your car has one.
-Your knock sensor could be malfunctioning, if your car has one.
-I think I may have heard that carbon build-up on the cylinder walls can cause premature detonation, but it has been a while. (Someone help me here.)

If you want to keep this car running, you need to take it to a qualified mechanic for a thorough diagnosis.

Sometimes getting the codes read from the computer doesn’t give you all the answers. I recently took a vehicle to Pep Boys to get the codes read on a Toyota Sienna with the “check engine” light on. Pep Boys gave me one code. Then I had the codes read at a Toyota dealership. The dealership came back with three codes. Evidently, Pep Boys was using an inferior code reader.

If you can’t afford to fix this car right now, you might try high octane fuel to mitigate the pinging, but that is only a temporary stop-gap measure.