i have a 2001 B2300 2.3 eng 5spd,2wd. when you try to accelerate to quick it jumps and misses. going up a hill and holding a steady speed it will start to jump and miss. flat out if you accelerate slowly it seems to do ok. seems to be worse under 2500 rpms. when it's idling and you step on the gas quick it hesitates before picking up. i've put in new plugs,plug wires,fuel filter and cleaned the maf sensor but nothing helps. any help would be appreciated

 

Well you've covered the two things that first came to mind, MAF & Plugs.

Have you checked the TPS sensors resistance over it's complete operating range???? If it's resistance doesn't change smoothly over it's enire range. or if the resistance is too high or low, or the V-Ref voltage to it is out of spec, the computer will get confused about the throttle plates true posiion & not change the fuel injectors duty cycle in time to keep the fuel trim from going lean.

Have you checked fuel pressure????

Have you inspected all the vacuum lines & hoses for leaks. This would include the HiVac, brake booster, PCV valve & it's hoses, & the vapor recovery system & it's hoses.

Have you scanned the computer for set, or pending trouble codes???? If so, post ALL the codes found.

Did this poblem come about suddenly, after some event, or slowly over time????

Just some more things to ponder, in trying to narrow down your trouble shoot.

Let us know what you find.

 

i have checked the vacuum hoses, have not checked the TPS or fuel press. i just bought this truck a couple of months ago and it was doing this when i bought it but it seems to be getting worse. i've put 12000 miles on it since i bought it. i'm away from home now on a work related trip, will check out the other things when i get home thanks PawPaw

 

Run 3 or 4 bottles of dedicated gas line dryer through it!! Don't do anything else just got to the store, dump it in the tank 3/4,1/2, 1/4 tank whatever drive it until almost empty refill with fresh gas and two more bottles one of iso heet and one of heet!!!
Once everyone got fuel injection they seem to forget the havoc water can reek!!
If you are having running problems $7.00 will fix it, Before you go throwing expensive sensors at a phantom problem!!!

 

OK, good feedback. Newly purchased used & was doing this when bought.

I'd run this puppy by your favorite autoparts store for a no cost computer trouble code scan & see if anything like set, or a pending code/s that haven't matured to turn on the CEL light, are stored, as they could provide good clues on your troubleshoot.

Well from your feedback, on all the things you've done to date, the vehicles history & no trouble code clues, it seems to me it's maybe fuel delivery related.

If so, then seeing as how it'll behave ok, IF the throttle is slowly opened, is it the fuel pumps inability to deliver enough flow, during sudden high demand times, like when the throttle is suddenly opened for grade climing, passing, ect, or is it the A/F mixture going lean, because the computer didn't realize the throttle had moved, or is the MAF slow to respond to the increased airflow!!!!

A fuel pressure & volume flow test, verses time & a TPS resistance check should answer those two questions.

Seeing as how it'll run ok, if the throttle is opened slowly, is a good clue & was one of the things that made me first think maybe it was a dirty MAF sensor.

Did you remove the MAF sensor to clean it, so you could get to it from all sides, or did you do it in place????

Did you use a non residual MAF formulated spray cleaner????
Any cleaner that'll leave deposts on the MAF sensors wire, will corrupt it's calibration.

The reason I ask about the MAF cleaning, is that I know one gal over on the MPT forum, that had to have her MAF cleaned THREE times, before the shop got it right!!!! lol

Over oiled coton gauze, or foam type air cleaners.
Poor fitting or damaged air filters or improperly buttoned up air boxes or air tubes, will pass dirty MAF sensor contaminating air.

Just some more thoughts to ponder.
Keep us posted on your troubleshoot.

 

i did take the MAF out to clean it, and did use a MAF cleaner. haven't done a code scan but will when i get home, will also try the gas dryer. thanks for all the input will post results when i get it all done

 

You can disconnect the MAF for testing purposes only, and the ECM will substitute an 'average' value for the MAF reading. If the hesitation goes away with the MAF disconnected, you may have pinpointed your problem. You should not leave it disconnected as your mileage will decrease, etc etc ad infinitum. This will leave a failure code in the ECM that will self erase after some number of cycles.
I would ditto the fuel pressure testing as what you describe is classic fuel delivery symptoms. Can your truck climb hills without any symptoms? If not, that points more to a fuel availability problem, which could be pump, filter, injectors or regulator. If there is crud in the tank, it could also be plugging the sock on the fuel pump pickup.
tom

 

Just a thought but you might check the EGR circuits. The EGR kicks off at WOT but if it doesn't you might get exactly what you're seeing - bad performance.

Might be a vacuum leak or probably just a dirty valve or passageway into the intake manifold. The port into the manifold is very tight and accumulates soot rather easily. But this sounds like the EGR isn't kicking off when it should.

 

Have the fuel injectors cleaned.

 

Quick question: I'm having hesitation issues as well (particularly at steady speeds under light throttle). After reading your post, I figured that I'd try disconnecting the wiring harness from the MAFS and seeing what happened - it hasn't driven that smoothly in years. Would this be indicative of a faulty or dirty MAFS?

 

yup.
t


I need more characters for this message to post, so here are some.

 

awesome.
thanks for your help.

 

Good trouble shooting Matthew.

If the MAF is dirty, you need to look up stream & find out WHY!!!!

Typical problems are improperly buttoned up, or damaged air boxes, or air tubes, improperly fitting air filter, over oiled foam, or cotton gauze air filter, if your using one of those.

Let us know what you find & how it goes.

 

Personally I would hook up a vacuum gauge and see what you get. should be 21 in-hg. It sounds like a vac leak to me.

 

Thanks for the reply pawpaw. Everything upstream (at least on the clean side of the filter) looks pretty much spotless. So I guess I should be leaning towards faulty rather than dirty. I'll get my brother-in-law (who has a farm mechanics course - many automotive steps above my pharmacy and biology degrees) to bring his multimetre with him to (Canadian) Thanksgiving dinner this weekend).