96 Jimmy Hesitation On take off

96 GMC Jimmy 4x4. About a month ago my Jimmy would not start. Had new fuel pump and all injectors replaced. Ran just fine for a couple of weeks and then started hesitation on take off after coming to a stop. Not every time but more times then not. All the following items have been replaced but it is still happening.

Fuel Pump
Fuel Pressure Regulator
Fuel Injectors
Fuel Filter
EGR Valve & Gasket
Plugs
Wires
Rotor & Cap
PCV Valve
3 Oxygen Sensors before the Cat. Converter.
Also the timing was set. Also I had an error code PO442 come on which says that it has something to do with the fuel tank venting. Would that cause the hesitation on it's own? I've already spent a ton but really want to get this figured out. Any suggests beyond what I've already done are greatly appreciated.

96 GMC Jimmy 4x4. About a month ago my Jimmy would not start. Had new fuel pump and all injectors replaced. Ran just fine for a couple of weeks and then started hesitation on take off after coming to a stop. Not every time but more times then not. All the following items have been replaced but it is still happening.

Fuel Pump
Fuel Pressure Regulator
Fuel Injectors
Fuel Filter
EGR Valve & Gasket
Plugs
Wires
Rotor & Cap
PCV Valve
3 Oxygen Sensors before the Cat. Converter.
Also the timing was set. Also I had an error code PO442 come on which says that it has something to do with the fuel tank venting. Would that cause the hesitation on it's own? I've already spent a ton but really want to get this figured out. Any suggests beyond what I've already done are greatly appreciated.

try checking your gas cap to make sure its holding presure

After I found out what that code meant I went out and made sure the gas cap was on tight. Is that all it takes or is there something else I should try? I'm not opposed to buying a new gas cap if you think it's worth trying. Obviously when they installed the new fuel pump they had to drop the gas tank out so I guess that would open up the possibility for something there to be causing the code. All hose were checked by hand to make sure they were connected and it was suggested that I take it to a dealer to do some type of smoke test. I'm sure that's not cheap.

After I found out what that code meant I went out and made sure the gas cap was on tight. Is that all it takes or is there something else I should try? I'm not opposed to buying a new gas cap if you think it's worth trying. Obviously when they installed the new fuel pump they had to drop the gas tank out so I guess that would open up the possibility for something there to be causing the code. All hose were checked by hand to make sure they were connected and it was suggested that I take it to a dealer to do some type of smoke test. I'm sure that's not cheap.

you should be able to take you gas cap to a shop and have it tested and they should not charge for that.if they do you should be able to buy a new cap for about $10.00 to $14.00. i hope this helps

Just a theory but a p0440 could also mean the purge solenoid is stuck open...this would let unmetered fuel vapor into the intake causing the mixture to go rich and bog down.


Mike

I really appreciate the suggestions. Here's an update. After topping off the fuel tank last night I noticed gas was leaking out from the rubber hose section between the filler tube and the gas tank. So I put new clamps on and tighten them more then they were so that most likely was the PO440 error. Plus I did put on a new gas cap. But unfortunately it drove fine last night for around 40 miles and this morning for about 20. But then on the way home from work it started to hesitate again. I thought I'd try the purge solenoid suggestion but being the mechanical rookie that I am, I found the MAP sensor and thought it was the purge solenoid. Any way when I pulled that off the rubber boot/gasket was all tore up so I figured that could be creating a vacume leak????? I got a new one and put that on and drove it a little bit tonight and so far it did not hesitate at all. So maybe that was the problem. My true test will be driving it to work and home tomorrow, 50 miles total so if all goes well after that I will feel pretty confident that I've fixed it. I will post after that to let everyone know.

Still not fixed. It's at the shop now for a few days so they can try to find the problem. Cha-Ching!!!!!!

MAF sensor is dirty.

Is the MAF sensor the same thing as the MAP sensor? If so that is the last thing that I replaced and it still hesitates.

Nope it is not.

It is the sensor in the air intake track inbetwwen the filter and the top of the engine.

I just got it back from the shop yesterday and they found several vaccum leaks at the upper manifold. They replaced two gaskets, one of which was chewed up pretty bad. I've drove it around 100 miles the last two days and it's running just perfect. Thanks everyone for your suggestions.