runs funny sometimes
 

hi all. i have an 01' 2500 hd 4x4 with the 8.1L and the allison..... sometimes when i am accelerating hard it seems like slips and sometimes it seems like it stumbles around 4000 rpm not completely wide open but close. after the stumble the check engine lite will come on..... it throws mass air flow code.. if i dont reset the code sometimes the light goes off on its own and sometimes i have to reset it.....the truck has a k&n cold air intake a stupid throttle body spacer that im sure doesn't do a dam thing. it also has an aftermarket mass sensor.... it will seem to run fine after it reset the trouble code it just appears to be random but it is way too frequent to be normal....what should i do??

http://ecx.images-amazon.com/images/...500_AA300_.jpg

EDIT: Also, unplug the senor and see if anything improves.

i didn't think it would even run with it unplugged

There are preset values stored in the PCM to allow for MAF failure. If you unplug it, the system will run off of the preset values and calculate the air/fuel based on that. If the truck runs better, then clean the sensor and plug it back in. Be careful though, it's a delicate sensor, and do not touch the little wires inside of it. Handle it carefully and do not touch the sensor. Let the cleaner dry and then re-install.

thanks for the suggestion. it needed to be cleaned really bad. but in doing the tests i encountered something else.... it seems to shift a lot harder when the MAF is unplugged, why would this be? also when i was driving around with the MAF unplugged it threw a code that referred to the throttle body and wouldn't run.... i was glad that i had the code reader with me so i could reset it or i would have had to be towed...

Well you could have just plugged the sensor back in.

But it will shift harder, because the PCM uses some of the MAF data to help the transmission know when and how hard to shift. For example, if you're WOT, and your engine is high RPM, the transmission wont want to shift hard because of how much power the engine's putting out. The MAF also help the PCM calculate air/fuel mixtures. All of that combined makes for a very important sensor.

thanks. i did try just plugging the sensor back in didn't matter until i reset the code for the throttle body it wouldnt go.. anyway thanks for the info...

So did cleaning the sensor help fix your problem?

it seems to have helped some im not sure if it has resolved the issue.. my check engine light hasn't come back on yet so that is a good thing. i haven't had a chance to floor it through all of the shifting yet to see if it stumbles cleaning made a difference for sure.

okay i went and romped on my truck and cleaning the MAF fixed it for sure the pinging went away which is good since im paying 4.29 for non-methanol super. so do you have any ideas of how to turn the torque management off in my tranny? allison thank you for your help