2001 Montana Hesitates When Accelerating

[USAF Sgt]

My Montana will hesitate a few times (RPMs drop) momentarily within the first few seconds when I accelerate. It only does it when the engine is warm. The hesitation only lasts for a few seconds and then seems to be alright and run smoothly. The hesitation pulsates, in other words it will die, then go, die go, etc. The engine service light came on about 2 months ago and I had AutoZone read the error code. The code said the coolant level was low. Well it wasn't so I had the radiater flushed and the temperatue coolant sensor replaced. My mechanic said the thermostat also was not working properly and replaced it. A few days after we did the radiater flush, sensor and thermostat replacement the hesitation problem resumed. My mechanic the spent a couple of days trying to figure out what was wrong but could not find anything. In fact, it would not hesitate for him at all. Anyone got any ideas as to what may be going on?

Thanks in advance.

[1Bradymichael]

Could be several things. When was the last time the fuel filter or air filter was replaced? Have you had the fuel pressure checked? It is possible that your fuel pump is starting to crap out, and a restricted fuel filter can cause this.
Might not hurt to run a good injector cleaner with a half tank of gas and then use as much of that as you can before you fill up. I would assume your mechanic has checked her over for a vaccum leak?

[USAF Sgt]

1Bradymichael - thank you for the response. The air filter was replaced within the last year. I don't think the fuel filter has ever been replaced but my mechanic did remove it and look at it. We are the original owner of the van so I should know this. I do not know what other troubleshooting steps he took. For now I'm going to stop buying Wal-Mart gas (has 10% of ethanol in it) and use Shell gas only. I also put a bottle of STP complete fuel system cleaner in it yesterday. We'll see what happens.

[1Bradymichael]

I would also go with something besides gas from wally world. They are notorious for buying the gas that is sent through the pipelines before and after a flush with one of those cleaning "pigs", and pipelines, at least around here, are flushed with good old water, and yes, some of it ends up in the gas, also try 87 octane without ethanol. Nothing against corn, it is all around me where I live, but it don't belong is gas. I get about 2 mpg less when I burn 89 octane with 10% ethanol.
Nothing against your mechanic, but looking at a fuel filter won't tell you if it is plugged, and it's an easy fix and fairly cheap.My guess is that if you can fly heavy iron you can replace it yourself
Also are the plug wires okay? Sometimes a warm engine will make a bad plug wire show up quicker. I would have the mechanic check the resistance on them to make sure one is not going bad. How many miles on the van, and how many on the air filter?

[LMP]

Originally Posted by USAF Sgt

My Montana will hesitate a few times (RPMs drop) momentarily within the first few seconds when I accelerate. It only does it when the engine is warm. The hesitation only lasts for a few seconds and then seems to be alright and run smoothly. .

Something lke that happened to me a few years ago: the MAF sense wire was dirty..meaning it will not sense air flow changes immediately, so it would take a few seconds to make up its mind. I just removed it and cleaned it useng alcohol and artist paint brush. Problem solved. Cost nothing to verify!

[JTZ2000]

I had this happen at road speeds under slight load like up a small hill. Found my positive battery cable was loose! Tightened it and issue was gone. 2000 pontiac montana, 185k miles