Mazda Protege5 Pinging

[WeenieHutJr]

2002 Mazda Protege5
About 2 years ago my car overheated from a stuck thermostat, that was when it first started pinging.
Since then it would ping on warm days only under a load in gear. Runs great, good power and fuel economy
I replaced the Timing Belt, Water pump, thermostat, Intake hose, Air filter, Knock Sensor, Spark plugs (wires soon), Cleaned MAF, used Seafoam and Techron, tried higher octane but still pings.
Any help is appreciated

 

[crazyoildude]

check the egr valve
could also be a burnt valve

 

[KevGuy]

Run a tank of high octane fuel and see if the Ping goes away.

 

[KevGuy]

Originally Posted By: KevGuy
Run a tank of high octane fuel and see if the Ping goes away.


Sorry, just noticed you already tried that....my bad.

 

[FetchFar]

I'd guess the pinging or ticking sound may be coming from a heat-damaged hydraulic valve lash adjuster. Either that or a slightly damaged fuel injector.

 

[tom slick]

When does it ping? Under load? Part throttle?

The variable intake manifold valves are known for rattling.

 

[WeenieHutJr]

It pings under a load at low RPM, 1.5k - 3k.
I did a vacuum test and it was ok.
How would I check for a damaged fuel injector?

 

[bdcardinal]

Originally Posted By: tom slick
When does it ping? Under load? Part throttle?

The variable intake manifold valves are known for rattling.


I have sold a couple of the intake manifolds on the P5's, but not very often. I seem to remember there was some silent recall or extended warranty on some of them, but it has been a while since doing it.

 

[Merkava_4]

Where are you buying your gas from ?

 

[OneEyeJack]

Have you done a pressure check on your cooling system to see if there's any damage done by the overheating?

 

[WeenieHutJr]

I've used Chevron, Shell, 76, and non top tier gas. No difference
I have not done a cooling system pressure test, what could be damaged besides the head gasket?

 

[Le_bow_ski]

I recently had the same problem with my '94 Miata.

Your O2 sensor helps determine the fuel:air mixture ratio, and a failing O2 sensor can cause a lean fuel:ratio, which will cause pinging. Try replacing the O2 sensor. Doing so was the solution to my low RPM pinging.

 

[WeenieHutJr]

I checked the o2 sensors with a scan tool. On acceleration sensor 1 switches from .3 to .8 and sensor 2 is steady about .7

 

[Le_bow_ski]

Even if the O2 sensor appears to function properly it can be sluggish in operation. In my case I began hearing light pinging while accelerating moderately hard from low rpms; something that had never been a problem before. I checked all of the usual suspects: plugs, gas, thermostat, etc.; no dice.

Then I had to have the car smog checked and it failed due to high Nox. High Nox is caused by high combustion chamber temperatures, which are also the result of a lean fuel:air mixture.

At that point I figured I had a lazy O2 sensor, even though it never resulted in a trouble code, and I swapped it out for an oem replacement. The replacement took care of both the pinging and the Nox.

I guess what I'm saying is don't rule out the O2 sensor too quickly, especially if there are few other possibilities.

 

[Le_bow_ski]

Have you checked ignition timing?

 

[Drew99GT]

I just put in a new 02 sensor in my 94 Corolla to see if that would eliminate the light ping I still get on hot days at lower rpms; I'll update in a week or so if it helped. The factory O2 didn't set any codes and still showed correct voltage, but when I pulled it out, it's was caked with carbon.

 

[artificialist]

Originally Posted By: WeenieHutJr
I checked the o2 sensors with a scan tool. On acceleration sensor 1 switches from .3 to .8 and sensor 2 is steady about .7

The upstream one is supposed to go from high voltage to low, and back again. However, sometimes the sensor will be too slow to react properly. When that happens, you can have sensor problems, yet not have an error code.

The downstream one should stay fairly constant. It exists to check if the catalyst still converts CO to CO2, and HC to H20 and CO2.

 

[WeenieHutJr]

Can I just replace the upstream sensor so should I do both?

 

[bdcardinal]

Originally Posted By: WeenieHutJr
Can I just replace the upstream sensor so should I do both?


Just do the front. The only purpose of the rear sensor is the monitor catalyst efficiency, it does not control A/F ratio.

 

[Gokhan]

Is it a sewing-machine-like sound? It could also be valve clearances out of adjustment. If you have never adjusted them, it's probably time to do so. Your engine seems to require a valve-spring compressor and adjustment shims.