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Let's talk throttle body

T

twizt3dfuc

NAXJA Forum User
Location
Alabama
Alright here's the run down.
My rock xj started giving me crap and prolonged starting( have to try, turn off and start and it'd hit everytime) so I replaced the cps.
After that it starts every time no problem.
So then I decided to attack the throttle response so it would be there when I pin the gas to make a climb.
First thing I tried was cleaning the iac. After cleaning the problem still lingered, rough idle until it was around 2k. Then I decided to clean the throttle body. Still a problem, replaced the map and it helped a little. This past weekend I just replaced the iac and the tps, now the jeep will not crank. I've read that the tps has to be adjusted(turned to proper voltage) and my question is does anything else have to be adjusted on or flashed?
It's a 99 4.0 with 98000 on it, it has a throttle body spacer if that makes any difference.
And while it has been sitting I've replaced plugs, cap, and button. So I don't know if it's gotten any better cause I can't get the sob to run lol
Any help would be greatly appreciated
 
OBD-II (1996+) TPS do not need adjustment, nor is it possible.

No-crank of the starter, or no-start of the engine ?
 
Starter and everything works fine... engine will spit and sputter but never actually take and run. It's almost like it only sputters after I let off the key.
 
Sounds like a bad CKP.
 
it could be a faulty cps. even with a bad iac and tps the jeep should still start. it will run like shit but it will still fire.
 
Allow me to clarify, cause ive been readijg alot the past few days, when i say cps, i mean CKP.When I did the ohm test between leads on the new one it matched because I first thought the same thing... not to say it isn't still at fault, is it possible that it needs to be shimmed or anything of the sort and it's causing it to fault read? It worked for the first 6 or 7 times that I cranked the jeep after replacing. Then it's almost like the jeep said F*** you and now just sits.
Only other thing I can think of is the gas tank. It is kinda in the elements and rain can sit where the pump drops in. I have pressure(visual) at fuel rail, but possibly quality of gas?
I'll make a video this afternoon, it's so hard to describe how it acts.
 
My '99 sat for 3 months after a situation very similar to this happened to me... Ended up replacing plugs, wires, cap, rotor, CPS, TPS, IAC, MAP,etc, and still nothing...

Turned out to be the ign coil. Myself and 3 others tested it numerous times, but when I swapped it out, it ran first try...
 
Re: Re: Let's talk throttle body

souske said:
What do you mean by (visual) fuel pressure?
Click to expand...

At the check valve I can push the Schrader and gas sprays almost to the left inner fender.
That was of course just seeing if fuel was making its way to the rail.
I will have a gauge tomorrow.
 
twizt3dfuc said:
Allow me to clarify, cause ive been readijg alot the past few days, when i say cps, i mean CKP.When I did the ohm test between leads on the new one it matched because I first thought the same thing... not to say it isn't still at fault, is it possible that it needs to be shimmed or anything of the sort and it's causing it to fault read? It worked for the first 6 or 7 times that I cranked the jeep after replacing. Then it's almost like the jeep said F*** you and now just sits.
Only other thing I can think of is the gas tank. It is kinda in the elements and rain can sit where the pump drops in. I have pressure(visual) at fuel rail, but possibly quality of gas?
I'll make a video this afternoon, it's so hard to describe how it acts.
Click to expand...

First off, if you have been cranking a lot, replace the plugs with a cheap set of Champions. The plugs can get wet fouled and without blast cleaning, they simply don't fire well. Put the original cps back in and get it started. They try the new cps again and if it quits, you have your culprit.
 
Re: Re: Let's talk throttle body

old_man said:
First off, if you have been cranking a lot, replace the plugs with a cheap set of Champions. The plugs can get wet fouled and without blast cleaning, they simply don't fire well. Put the original cps back in and get it started. They try the new cps again and if it quits, you have your culprit.
Click to expand...

Actually I have already swapped the cps back. Didn't consider the plugs though maybe 20 cycles on them
 
Last edited:
Just went through this with my 96, made pressure, just not enough. 39psi, swapped in a new regulator and got it up to 42. A new pump got it back to 49psi where it should be.

It would barely run on 39 psi of fuel pressure.
 
When you are installing a Crank Position Sensor, are you putting a new felt pad on the tip of the sensor for the gaping to the flywheel? If you aren't, you may have trashed two sensors. I get the pads from the service department at the dealership... The usually will just give ya some. next, unplug the Crank Position Sensor and the C1 connector on the PCM (the black connector closest to the front of jeep. Read pin 17 on the C1 to pin 3, Pin 8 to 1, and pin 4 (sensor ground), to pin 2. Pin 8 on the PCM C1 connector is the sensor signal.. Make sure with both connectors unplugged, that it does not read to the 5 volt (pin 17), or sensor ground (pin 4). The sensor ground at pin 4 supplies ground to all of the 3 wire sensors... Pin 17 supplies 5 volts to all 3 wire sensors also...

If a sensor ground or 5 volt wire is shorted anywhere in the system, it may be hell finding it. I've found that most of the wiring in the Cherokee after 14 years of being in the engine compartment, will literally melt together. When this happens, you will have to pull the wires back apart usually at the sensor, and check the wires for thin insulation..
 
Believe i found it guys... it's the gas itself. P
2upa3a5e.jpg

On purge the fuel looks like chocolate milk lol
 
bshack said:
When you are installing a Crank Position Sensor, are you putting a new felt pad on the tip of the sensor for the gaping to the flywheel? If you aren't, you may have trashed two sensors.
Click to expand...
I know of no XJ that uses a spacer for setting the air gap. That is typically done on CPS with one bolt, not two.
 
Talyn said:
I know of no XJ that uses a spacer for setting the air gap. That is typically done on CPS with one bolt, not two.
Click to expand...

You sir are correct. The manual does show installations for single and dual hole installations. The single hole requires felt, two hole installations show specially machined screws to install the sensor to the proper air gap.
 
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