ok... here it is.. running the truck empty.. in od.. running about 60 up a steep hill... steping on the peddle.. running up around 20 psi.. then bang... boost is cut by half... and so is the power... the code that i got was a "pcm error" code i don't remember the number... so what is going on with my mule..? i assume the pcm is a "power control module"..? what does it control and could it be responsible for what is happening..?

 

Any chance on getting the number?

 

Well John.......we really need to know what that code was. That will tell us what needs to be checked.
PCM is short for Powertrain Control Module. It controls everything that has to do with the engine and transmission. It bases these controls and adjustments on a wide range of sensors which includes a speed sensor way back in the differential. That code will tell you what the PCM didn't like.

 

i should have written it down but i didn't... i didn't have a pen... and i cleared the code...

 

ahhh... well... i'll write down the number the next time i get it.... now.. the big question... can the pcm have that kind of effect on the engine that it would cut back on the power that much..? it was doing this a couple of weekends ago when i was towing...

 

I carry a pencil and a small pad in my console......because they say that memory is the first thing to go........I can't remember what the second thing is. LOL
Till you see it again......some thoughts........losing half of your boost all of a sudden.......one of two things comes to mind.....as was stated before. The boost pressure is escaping at a boot.........or your turbo is stalling.......and the built-up pressure in the IC is overcomming it and blowing back out the air filter. I don't think you were over-reving it.......kinda hard to do when under load unless something starts slipping like a clutch......I think you have an auto anyway....right? If so, that blows that theory. Those are just some of the things I'd be thinking about. When you start up that grade next time.......try to watch the tach, and see if the revs take a drastic jump towards red line when it happens.....that will tell you if something is slipping under load, and allowing the engine to red line......thus causing the PCM to start defueling. I think you already told me that you have the MAP sensor spoofed......so that shouldn't figure into this problem. Just some things to think about.

 

The PCM is the BOSS......based on the information we let it have access to. By spoofing the MAP sensor, and never allowing the PCM to see what it would consider a "over boost" condition.....we get more power out of the engine. If the PCM sees the RPMs going too high......it will start defueling the engine until they get back to a normal range........or if it is too drastic.....it will kill the engine completely. So yes, it can cause drastic charactoristic changes.

 

that is why i call this weird... nowhere near enough psi to trip the map, even if i didn't have it fooled... it only happens in overdrive... 20lbs of boost and low rpms... and the change is instantaneous... absolutely feels like a defuel... is the pcm capable of defueling like this..?

 

strange thing about this... it defuels but the power after that is consistant... it feels like half the power... and it doesn't come back till you let off for a few seconds.. i would think cps, but it doesn't seem like that's it... this is a deliberate condition caused by electronic control...

 

That code will help narrow the possibilities........we should be able to figure it out.

 

ok... i'll be watching for it everyday... i gotta tell ya... this sucks...!

 

I know......but in the end.....hopefully you'll be able find and correct the problem.

 

yeah... with a little help from my freinds..!

 

hey johnny....what about tryin that identicle run again and see if it will do it? that way you can read the code and record it....i dunno, just a thought

 

man... you read my mind... gonna do that tommorow...!