Hello!

First of all, I joined this forum in 2009, but this topic is my debut here, since is really hard for me to communicate in English... I can read a bit, but writing is much more difficult. So, anticipating any mistake I may commit on the language, sorry for my (really) bad English!

I'm having a strange issue with my 2000 Jeep Cherokee (since it's made in Argentina, the engine is just like 1998's), and I decided to create this topic to describe it, so maybe someone can help me.

The car was running fine until two weeks ago, when I decided to wash the engine bay. I know it's not very safe to do this, but I've already done it a dozen times, and have never had an issue. I took every care recommended, like disconnect the ground terminal of battery, cover the sensible parts, dry everything out with an air compressor before reconnect the battery, etc...

After the cleaning, the engine starts almost normally, and I can barely notice anything wrong at idle. It runs almost smoothly when the gas pedal is lightly pressed and the RPM are under 2800. But, when I press the gas pedal to the floor (or something more than 60%), the engine stutter like hell, the car loses (almost all) power and I can hear some shootings noise (backfire?).

I've already sprayed electric contact cleaner at the every sensor plug I've found at the engine bay, dried all spark plugs, the coil and the distributor, and no luck at all. Also have checked the TPS with a Chinese OBD reader and the Torque APP for Android, and it seems to be working fine (although I did not checked it the proper way - I don't know exactly how to do it)..

Anyway, someone have a clue about what is happening to my XJ? I can't think of anything else to check, any help is appreciated!
Just remembering, this was 2 week ago and, until now, the behavior remains the same, no improvement!

Thanks in advance!

 

What 'sensible parts' did you cover out of curiosity?

 

The ABS module, the ECM (I think is called ECM, located near to the air filter) and the distributor cap. That's all that I've covered. Did I miss something important? By the result, I presume so...

 

I believe the most likely cause would be your Throttle Position Sensor (TPS) located on the throttle body. They do not like water but usually end up being fine after they dry out completely. That's where I would start but you might want to wait for others to offer suggestions before you start pulling parts.

As far as your English... it's much better than many here who were born and raised in the U.S.

 

Is it doing this in neutral, or in drive?

 

Thank you for your comment!
As for the TPS, it was my first suspect too. But the reading in Torque App (Android) suggests that it's working fine. I've compared the results with a friend's XJ, and it was similar to mine...
Any tip about an easy TPS testing? I have a multimeter...

 

In drive.

 

I agree with F1Addict about the TPS.

You can check the operation of the TPS with the engine off and the ignition switch inthe RUN position by hooking up your scanner and monitor the TPS %. It should read about 18-19% when the TPS is at the idle stop, and when slowly advancing the throottle, it should move to around 93-95% at wide open throttle. See if there is any interruption to the % readout when you are advancing the throttle. By your description of the engine acting up, a dead spot in the TPS should show up.

This is a quick way of checking the TPS without getting your hands dirty but it's not dead nuts conclusive.

 

That's exactly what I've done! At the idle stop, it is 17,3% and at full throttle, 79,8%. I didn't notice any interruption to the % readout.
By the way, before the problem have started, the reading was about the same (17% and ~80%)... but I still suspect of the TPS.
Anyway, tomorrow I will test my XJ with the TBI of my friend's XJ. I guess it will put an end to this suspicion...

 

The use of a hair drier to (carefully) heat the sensors on the throttle body for awhile to accelerate the dry-out process may help. Also, the Distributor, coil and crankshaft position sensor.

Those % readings look good.

 

How can I dry the crankshaft position sensor? just the plug or do I have to pull it out?

 

Just the plug.

 

Thanks! I will do this right now.

Edited:

Done it, without any improvement. I believe after 2 weeks everything that was wet already dried, am I right? Or the rainy weather (it rained a lot the last two weeks here) can prevent the plugs from drying?

 

Here goes one little photo of my XJ!

 

just thinking out loud...how about bad ignition wires? moistuire inside the dist cap....