Initial gas pedal hesitation and now idle problems

For about the last year and a half I have noticed that after I have run my XJ and shut it off for a bit when I get back in and start the truck and drive I sometimes get strange throttle response when first taking off in the truck. The throttle control will start to fall off and if I push the pedal harder it feels like the motor is going to stall or maybe even backfire so I let off the gas and the push the pedal again and it works fine for the remainder of the drive until I shut the truck off again and it sits. It doesn't happen every time but it is an intermittent problem. Plus in the last day or so I have also had idle problems on 2 occasions. My truck wouldn't idle at all when I would start it. Once when it was warm and once in the morning when the truck was cold on first morning start. The first time the problem was fixed after I put it in gear but the cold start wasn't so easy. I had to power brake using the gas pedal to keep the car running and put the car in gear and drove the car for a bit til the idle seemed to work itself out. This has only happened 2 times but it really has me worried.

Is this a common problem? Are the problems related?

Any help would be much appretiated,
Robert

What year and engine will be THE first responce you will get.There I just did it! But seriously it sounds like fuel pressure? fuel pressure regulator? sticking TPS? Vacum leak? Map sensor hose leak? Loose ground?..a lot could be it.

does it do it when hot? could be Heat soak, the 4.0s are known to have that problem

This is really a question that belongs in the OEM tech section but it sounds to me like TPS.

The XJ is a 1998 4.0 Sport. As far as pedaling problem goes it seems to do it at normal operating temps only. The reason this post was put here is because I have some after market parts on my motor like header and cold air intake.

Thanx for the responses so far
Robert

jeeperjohn said:

This is really a question that belongs in the OEM tech section but it sounds to me like TPS.

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this.

TPS or CTS (Coolant Temp Sensor). The TPS can be tested, the CTS is inexpensive enough to simply replace. A weak or slow to respond CTS will give boggy acceleration with light to moderate gas pedal. Wide Open Throttle will seem as normal, since the sensors are ignored by the PCM at WOT.

Sounds like what I just went through. Mine would idle poorly and sputter but all within 120 yards of first taking off. I would get on the gas and it would bog down so I would let off the gas and get back on it and it would be fine. I just replaced by TPS and my MAP sensors. Bought my MAP sensor off ebay for $18 free shipping. Installed it yesterday and I have yet to have the problem again. Best of luck.