1999 4.3L Jimmy - Issues after starting when hot
 

Hello All,

Have been dealing with a fairly strange issue, and am looking for any ideas to tackle to get this taken care of.

1999 GMC Jimmy 4x4
4.3L Motor
100k miles

Basically, it amounts to have almost zero acceleration, but only after restarting the truck when it's hot (say like, stopping to get gas). Doesn't matter whether or not I gently accelerate, or push it right to the floor, it just crawls along. After a little bit, it seems to clear up and act completely normal. Takes about 10-15 seconds or so, and then it's great. Like, full acceleration after that if I put the hammer down on it. The fact that it immediately clears up after makes me wonder if it's ECU or Transmission related? If it was hard mechanical, I feel it would persist continually rather than clear right up.

As I was typing this, I realized that this is most common after fueling up the vehicle. Could it be somehow flooding it when turning it off? Still starts just fine though. I can run some more tests this week, and try a few different scenarios to see if presents elsewhere with a short off/on period.

It runs and drives mint when it's cold or warm, as long as it doesn't get turned off and back on again.

In no particular order, I've changed out the following bits in the last few thousand KM's with no success:
Fuel Filter
Air Filter
Injector Spider
Spark Plugs
Plug Wires
Cat Converter

Would really appreciate any help on this.

Thanks!

Any codes?

Sorry, missed the notification.

No check engine light at any rate, no error or warning lights of any kind.

Just a weird period of no acceleration.

Is it possible there are stored codes that aren't throwing a CEL tucked away? I haven't tried putting a scanner on it while it's happening, but I do have access to one. I'll give it a try tomorrow and report back.

I have confirmed however that it occurs after any short shutdown, up to about 30 minutes after I turn off the truck.

Had a chance to test this out, no engine codes thrown or stored (before, during, or after) when this issue occurs.

Is it possible it's a fuel issue? When I put the pedal down, it wants to try, but it's like there is nothing there. I kind of feel that if the engine was running correctly, it would throw a lean code from lack of fuel though.

Additionally, can confirm that changing gears by hand on the automatic shifter makes no difference. I can feel the trans change gears, but putting the pedal down still results in a lack of power and acceleration.

Will keep tinkering and see if I can come up with something else. Might try changing out the MAF sensor and see if that solves it..

May want to research the TPS (Throttle Position Sensor). Once it gets hot it may be failing ?

Would it make sense that it clears up within 20 to 30 seconds after though? After that initial bump and issue when starting moderately warm, it clears right up and doesn't present at all until the truck is shut down and restarted. That being said, it's cheap enough to throw one at it and see what happens.