Weird missing problem 4.0L

[JeepSA]

Hi

I have a 98 4.0L XJ. After a recent long trip I started to get a missing problem. The motor would start to idle rough loose its revs. and then starve. The problem was intermittent but got worse to the point wher you couldnt drive the car.
I took it to JEEP to be fixed. So far I have replaced both O2 sensors, the crank sensor, the altitude/octane sensor on the throttle body and the absolute temperature sensor.
The problem is better, but now when running the car under acceleration it seems jump to neutral and gear down. When on a level road and not accelerating everything seems fine?
When I start her cold she also revs very high(2000) for a couple of minutes and then settles down. The first pull off of the day also leads to a starving scenario where the motor wants to die and idles erratically, then she settles in again?

Any suggestions would be greatly appreciated, could this relate to the TPS(Throttle Position Sensor)

Regards JeepSA:confused:

	Crank position sensor A crank sensor is a component used in an internal combustion engine to monitor the position or rotational speed of the crankshaft. This information is used by engine management systems to control ignition system timing and other engine parameters. Before electronic crank sensors were available, the distributor would have to be manually adjusted to a timing mark on the engine.

	Throttle position sensor A throttle position sensor (TPS) is a sensor used to monitor the position of the throttle in an internal combustion engine. The sensor is usually located on the butterfly spindle so that it can directly monitor the position of the butterfly throttle valve. The sensor is usually a potentiometer and therefore provides a variable resistance dependent upon the position of the butterfly valve (and hence throttle position). The sensor signal is used by the Engine Control Unit (ECU) as an input to its control system. The ignition timing and fuel injection timing (and potentially other parameters) are altered depending upon the position of the throttle, and also depending on the rate of change of that position. For example, in fuel injected engines, in order to avoid stalling, extra fuel may be injected if the throttle is opened rapidly (mimicking the accelerator pump of carburetor systems).

[Sparky-Watts]

Could be, but also sounds a bit like a plugged fuel filter. Have you changed that? My YJ acted pretty much the same way about a year ago (except I don't recall if it idled up high on start-up), so I changed the fuel filter and it all went away. I always start with the cheap easy stuff first. I guess that's because I'm an optimist and think it's gonna be something cheap and easy....either that,or I'm just cheap and easy...........

[Sparky-Watts]

Also, have you checked the MAP sensor? Or do you have one? Or is that what the altitude/octane sensor is? My wife's Camry acted funny like that, and the fuel filter didn't help, but the new MAP sensor did.

[mujaman]

try replacing the TPS sensor. no guarantees that will work, but its worth a shot and its one of the first things i would have done. you can pick one up at NAPA for about $60 and put it in by yourself in less than 30 minutes. its a simple bolt-on piece on the side of the throttle body...

	Throttle position sensor A throttle position sensor (TPS) is a sensor used to monitor the position of the throttle in an internal combustion engine. The sensor is usually located on the butterfly spindle so that it can directly monitor the position of the butterfly throttle valve. The sensor is usually a potentiometer and therefore provides a variable resistance dependent upon the position of the butterfly valve (and hence throttle position). The sensor signal is used by the Engine Control Unit (ECU) as an input to its control system. The ignition timing and fuel injection timing (and potentially other parameters) are altered depending upon the position of the throttle, and also depending on the rate of change of that position. For example, in fuel injected engines, in order to avoid stalling, extra fuel may be injected if the throttle is opened rapidly (mimicking the accelerator pump of carburetor systems).

[dropseys]

My XJ started with problems like that and it ended up being a bad fuel pump. I also read on here where someone else had a similar problem and it was the computer.