Engine pinging

[JessC]

Base timing was tested and is at what it's supposed to be

 

[Shran]

I guess knowing that your short block was not changed confirms to me that this is not a mechanical issue with the cam, timing chain, etc.

Did you get your original heads back from the machine shop? Wondering if there is some issue there, maybe you got someone else's newer heads and that changed your compression ratio?

If you are sure you have your original heads and there was not an enormous amount of material removed, greatly altering your c/r, then I would lean towards this being some sort of electrical/PCM/ICM malfunction like we originally discussed.

 

[JessC]

Yes I got the original heads back from the shop. Truck was pinging before the engine rebuild so I don't think it is the heads. And PCM AND ICM has been replaced. I don't know do I just have to drive it awhile for the PCM and ICM to relearn?

 

[Bgunner]

Is it possible that you have an injector/s starting to get clogged so the fuel isn't atomizing properly causing your ping?

 

[JessC]

It could be possible but all injectors are brand new.

 

[Bgunner]

In that case probably not then.

 

[sgtsandman]

You could try premium fuel and see if it fixes the issue until you can figure out the root cause.

 

[Shran]

Think he said early on that he was running high octane fuel. Probably can rule that out.

Wonder if a colder heat range plug would help? Autolite AP105 is the stock replacement... heat range 3. Looking at their cross reference it appears that AP104 is the next colder plug, heat range 2, and AP103 is heat range 1.

You don't have EGR on that truck do you?

 

[sgtsandman]

Think he said early on that he was running high octane fuel. Probably can rule that out.

Wonder if a colder heat range plug would help? Autolite AP105 is the stock replacement... heat range 3. Looking at their cross reference it appears that AP104 is the next colder plug, heat range 2, and AP103 is heat range 1.

You don't have EGR on that truck do you?

I reread through. He did say he was running 93 with an octane booster. I forgot about that.

 

[Bgunner]

Wonder if a colder heat range plug would help? Autolite AP105 is the stock replacement... heat range 3. Looking at their cross reference it appears that AP104 is the next colder plug, heat range 2, and AP103 is heat range 1.

I thought of this earlier but what had me stumped is that the engine pinged before the top end rebuild. The reason why I didn't put this out there was the question of Why. Why would all of a sudden the engine needs a colder plug even before the rebuild? When you go to that extent it is best to know why the engine is unhappy with the stock plugs.

Here is a thought for more knowledgeable minds to chew on and consider:
Since the pinging happened before the top end rebuild this makes me think it could be in the lower end. Is it possible that a wrist pin is just starting to get a little sloppy where the timing being advanced by the ECM would cause the piston to slap the skirt? I know that when they go it is usually a constant slap like what the 80's Chrysler 2.2L had, them things sounded like a sick popcorn maker, but just on the beginning effect of it?

 

[Shran]

I thought of this earlier but what had me stumped is that the engine pinged before the top end rebuild. The reason why I didn't put this out there was the question of Why. Why would all of a sudden the engine needs a colder plug even before the rebuild? When you go to that extent it is best to know why the engine is unhappy with the stock plugs.

Here is a thought for more knowledgeable minds to chew on and consider:
Since the pinging happened before the top end rebuild this makes me think it could be in the lower end. Is it possible that a wrist pin is just starting to get a little sloppy where the timing being advanced by the ECM would cause the piston to slap the skirt? I know that when they go it is usually a constant slap like what the 80's Chrysler 2.2L had, them things sounded like a sick popcorn maker, but just on the beginning effect of it?

I know... it is weird. If it had not been apart and inspected, I would suspect carbon knock. It would be interesting to see live data on spark advance in this case to see what's going on.

My buddy rebuilt a 4.0 and it immediately developed a stutter right off idle when warm. Eventually I heard he found that it had something to do with using an auto ECM with a manual trans and having a slightly better than stock engine with the shift solenoid codes present in the computer, and something was causing it to pull out timing and lose power intermittently. I don't know if it ever got fixed but there are some weird things that can happen.

 

[JessC]

I'm gonna pull the front half of the motor to inspect the timing set. Truck over heated yesterday with SPOUT plug out. Pulled over to let it cool and plugged SPOUT back in. It didn't ping the rest of the way home. Still stumped.

 

[Shran]

Maybe the timing chain or gears are worn and it jumped time? Weird.