[purple_jeep]

Hi Guys,

I have a 98ZJ and lately it has been playing up. When I go to start it it takes longer then normal to fire (eg turns over more times then before).

Also when driving it has in the last few days suddenly lost response to the throttle. I put my foot on the accelerator and the RPM does not change at all just drifts back to idle?? First time this happened I was coming up to the lights just before I started to brake. Stopped at the lights put it in N and pushed on the accelerator peddle until it woke up.

As I drove away from the lights it did it again pushed on the accelerator a few times, it back fired and woke up?? First time it has ever backfired on me before...

Also my ABS light is on but I took it to a brake masters and they could not get a code from it?

Thoughts?

Cheers

Chris

[Some_Anchovies]

sounds like the engine is running really lean. Check your O2 sensors and vacuum lines. Probably got something wrong there.

The wanting to die when giving it more open throttle sounds like not enough gas, so its dieing (symptom my 3wheeler had before I adjusted the carb). The backfiring usually comes from too rich of a mixture, so it sounds like pumping the accelorator gets enough gas to wake it back up, but the large amount of gas that is getting in there is still burning in the exhaust.

[rm2001wj]

With a fuel injected (not carburetted) engine, pumping the accelerator pedal doesn't put more gas into the intake manifold. Only air goes through the throttle body. Sounds like the main problem is a faulty throttle position sensor (TPS). It's easy to replace and doesn't cost a lot.

There could also be a problem with the idle air control (IAC) solenoid. Usually it can be cleaned, although replacement is not difficult or very costly.

Do the TPS first and see what happens.

[ZJPunk98]

I had the exact same issue. After replacing the TPS and cleaning the intakes, a change of O2 sensors fixed the issue.

[purple_jeep]

One other interesting symptom i noticed today while driving, if I was cruising at speed and removed my foot from the accelerator to slow down a bit or just coast the rpms could be sitting at 1500 and then it would pulse down to 1250 then back to 1500 sit there for a second or two then pulse down to 1250 again?

seems very strange to me. TPS was my thought too I will prob grab a replacement one of them.

With the O2 sensors, do i need to replace both?

Cheers

Chris

[jeepheller98]

i would replace the upstream one, the second one after the cat is just to see if the cat is alive, upsteam controls the air fuel mixture