Engine Hesitation after stoping

[Mike1]

I have had 2 XJ 4.0L Jeeps one a 96 and the current a 98

Both vehicles have had the same problem leading me to believe that it could be a common problem?

After driving the vehicles and stoping for a while, upon re-starting the vehicle and driving off, there is a huge drop off in power for around 5 - 7 seconds. It is similar to when a engine is starved of fuel or there is a electrical miss of some sorts. (The cars both start fine)

I then have to let the car sort of idle slowly forward and then continue as normal without further problems?

Any suggestions?

Mike :?:

 

[MudderChuck]

4.0L Autobox servicing?

Just a guess, but the first few seconds after a start up (used to be 15, think it´s 7-8 now) the computer idles up the motor. After the motor temp. passes 140 or so the computer switches into yet another mode.
Could be a dirty idle motor symptom, but I´m just quessing, most of my experience is with pre 91 XJ´s.
I typically, let the RPM´s drop to near normal before I put it in gear. Don´t often need to do a "fast get away".

 

[XJNick]

Hi,

I know exactly what you're talking about, as I've experienced it before with my '88 cherokee. I never really determined what was triggering it before removing the 4.0L from it, But I have a very strong feeling it is caused by the Throttle Position Sensor (TPS). I feel this way because my TPS was old and didn't seem to operate smoothly throught the potentiometer's range. I also was thinking it could be due to a dirty Idle Air Control Motor (IAC), but mine had been cleaned and inspected along with the throttle body and I still had the problems.

Mine would do this whenever. Cold start/ warm start/ in the middle of a drive, would still do it, but not too often.

hope that helps :mrgreen:
-Nick :!:

 

[Mike1]

Thanks Nick

Where would the throttle position sensor be located and can it be cleaned instead of replaced?

Mike

 

[Mike1]

Thanks Nick

Where would the throttle position sensor be located and can it be cleaned instead of replaced?

Mike

 

[XJNick]

Hi,

The throttle Position sensor is mounted to the Throttle Body (near where the big air duct from the air-cleaner attaches to the engine). The sensor has either a flat 3-pin plug or square 4-pin plug and has an arm which you will see move when pressing on the accelerator. No, it is not cleanable. it is adjustable by loosening the two torx bolts and pivoting it until the output voltage between (I believe) pin B and ground is 0.8 volts with the accelerator pedal NOT being depressed. But note that even if it is outputing the correct voltage at closed throttle and at WOT (which is about 4.8-5.0 volts), it could still be bad. You'd have to check for a clean linear output across the sweep of the TPS potentiometer to be sure. :mrgreen:

-Nick :!: