97 V8 Missfire at low rpm loaded

[griggs]

My 97X 5.0L V8 AWD AT is missfiring on what feels like one cylinder whenever the engine lugs down below 1500 rpm and the throttle is opening. Otherwise it runs perfect. Have changed plugs. Wires and coil packs ohm out OK. Also ran a tank of FI cleaner through it. Anyone got any ideas before I start throwing $ at this problem?
Thanks - Jerry

 

[410Fortune]

is the check engine light on?
How many miles?

did you clean the MAS?

 

[griggs]

Sorry. No the CEL is not on and there is no codes. I scanned. The vehicle has 122k miles. I think the coil packs and plug wires are original. And no, I have not cleaned the MAF.

 

[410Fortune]

first thing to do with any kind of stumble like this is clean the MAS.

coil packs generally last the life of the truck.
PLug wires could probably use wither replacing or at least a clean and lube.

 

[griggs]

Will clean the MAF and report back. Thanks.

 

[griggs]

Reporting back. Well I cleaned the MAF Sensor as described by another post on this site and I think it is fixed! Two days of driving and no missfire (or stumble or whatever) noted. It did act funny until the PCM relearned the fuel trims etc but after that just like a new Buick. And, frankly I am kind of surprised since the MAF Sensor did not look dirty. Just a light coating of black dirt everywhere which is now gone. OBTW I used NAPA Air Intake Cleaner to clean things. Thanks for the suggestions. This is a great site - period.

 

[410Fortune]

EXCELLENT NEWS!!!



Another one into the history books.

Those little hot wires get coated with crap and even though you cant see it the gunk can effect the readings big time.

The way a MAF works in laiman terms is the electricity from the computer heats up those sensor wires, the air passing by cools them off. the change in temp is tunred into a signal voltage and sent back tot he PCM.

Any residue, blockage, or gunk in there and the signal will be FUBAR'ed
It is a very sensitive meter

 

[ajr0311]

MAS? MAF? What are these?

 

[ajr0311]

Mass Air Flow and?

 

[410Fortune]

Mass Airflow Sensor.

Mass Air Meter
Mass Air Flow

They are all talking about the same thing.
In the industry you will find this often, an Idle Air Control valve or IAC to a Ford guy may be a idle Air Flow Valve to the counter guy at Autozone.

MIL, CEL same thing...it goes on and on

 

[Glacier991]

A tip of the hat to 410Fortune for helping fix yet another one. Good call. Often no one thanks us enough when we hit a home run. I'm saying thanks from all of us on this one.

Guys this forum is top notch with great folks on it. Guys like 410Fortune.

 

[410Fortune]

ah shucks thanks Glac!
I try to give back some of the help I have gotten over the years.....