hi i have been pulling my hair out with this problem on my 99 jimmy 4x4 sometimes for the past year when tring to pass or sometimes from a stop i get a loss of power between say 2800 and 3500 rpm it doesnt miss just momentary loss of power i have replaced all the obvious stuff fuel filter, plugs, wires, cap, plugs, o2 sensors all of them and replaced upper intake gasket and tb gasket.it has only thrown a code once when it was acting up i really kept reaming it while it was doing it and i threw lean bank one and lean bank two but that was a year ago and no codes since this is really strange this may help sometimes it is worse after i reverse in one direction then take off in another. sometimes if i start the drive just for a minute then shut off for a minute then go to pull out and hit the gas it does it. sometimes it doesnt do it at all but when i need to pass it does it. the fuel mileage is good i am completley stumped on this one thanks for your time and your service to all us diyers out here.
DateStamp: 11/27/2007 8:53:39 PM
IP:198.208.159.19



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maybe a maf sensor, my 99 was similar as yours, really hope this helps, and if it is the maf sensor, DONT BUY CHEAP!!!!

 

DO NOT replace the MAF sensor on a whim... If you do anything, clean it first (search for proper cleaning procedures/procautions).

 

thanks i was wondering if it was the maf i sprayed it once with brake cleaner and i swearthe problem temporarily stopped thanks

 

Well, I wouldn't recommend using brake cleaner to clean it. Most brake cleaners leave behind a residue that will harm the sensor elements. Clean the MAF with MAF specific cleaner which can be purchased from pretty much any autoparts store. I'm betting that the MAF elements are pretty dirty. Just be careful.

 

thanks can i remove the screen and take the maf apart and do you think the syptoms i described to you momentary loss of poer and lean condition once while it was acting up i kepy the pedal to the floor and had a lean backfire through the throttle body but as long as i dont push the gas down to hard it always recovers and runs fine otherwise thanks i have never had to replace a maf before but from what i have been researching they slowly deteriorate over time causing a weak signal have you had any experience with these thanks for your time

 

I would not recommend removing the screen from the MAF. It was put in there to make a smooth, laminar flow of air through the sensor so the PCM had an accurate reading of the air flowing through the sensor. By removing the screen, the velocities through the sensor could be uneven across the cross-section, causing inaccurate air flow readings.

What is odd about this issue is it only happens at a specific RPM range... Is it consistently occuring during this range, regardless of throttle position? Or is it more tied to a throttle position? You may want to test the TPS sensor as well ot make sure that it doesn't have any dead spots in its travel.

 

Have you done the fuel pump pressure test? Mine did the same and shortly after I had the fuel pump fail. Worth a look.

-sp

 

thanks for all the replies i unhooked the maf sensor and drove it for a couple of days and it ran excellent it had so much more power than it has had in the year and a half since i have owned it. since it ran so welland never did the lean out hesitation, i went ahead and replaced it with a cardone unit from autozone so far so good i will keep you posted thanks for all your help steve.

 

Sounds good! Did you try to clean your original before dropping the $$$ on a new one?