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Hey All,

I have had my jeep for around a year, the only issue I have had is a bad master cylinder that had to be replaced, but since then no problems as a daily driver. Over the past few weeks she has suddenly started stalling on me and I wanted to get an opinion on what the symptoms point to so I can try to pinpoint the issue. So far I have tried replacing the ignition coil, and that did not fix the overall problem. Here are the symptoms:

  1. 1987 Jeep Wrangler Sport YJ 2.5 TBI.
  2. Jeep has started to stall at stop signs and stop lights, but only after getting warmed up (15 minutes or so). Stalling completely takes out brakes and power steering, but battery shows fine, and all interior electronics work. 
  3. When turning the key on, I can hear the fuel pump going, and it doesn't stop. Previous owner said to not turn the key to accessory and keep it there as it will kill the fuel pump as it doesn't turn off. This doesn't seem normal to me?
  4. Jeep idles high when started, goes down to normal idle, and once warmed up will idle rough and low, 600-700. Idling will not cause her to die though, only movement and shifting. 
  5. Jeep will not start back up once shes been running or after she stalls unless she sits for 10-15 minutes, and she will start fine but a little rough.
  6. 6 Months ago or so she started not starting occasionally unless I pushed the gas slightly as I cranked and she would then squeal and start rough.

My action list for what I think might help or fix the issue, just waiting for a non rainy day:

  1. Check the ISCM module, clean it and check that its working (Whats the best process for making sure it is working as it should be?)
  2. Clean the throttle body and check for even fuel spray
  3. Replace crankshaft position sensor
  4. Replace fuel filter
  5. Replace fuel pump relay in hopes of stopping the thing from constantly running
  6. Check fuel pressure
  7. Replace fuel pump (My final resort, I will have a shop do this as I do not have the means)

I am including a picture of my throttle body, how do I go about cleaning it? I cannot seem to find much about this online, every video or site shows what I am guessing a different fuel injection system. Do I remove the injectors on the top and clean underneath with throttle body cleaner? The jeep is 30 years old and is in really good shape for its age, I don't want to screw anything up, but I want to learn all I can.

I guess I mainly want to know if I am in the right direction. I appreciate it. I have also read this thread:

And it was also extremely helpful. Thanks!


(Sorry for the long post, I wanted to give as much detail as possible)


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Tristan...If the wiring is original and not modified, the run-on fuel pump and Accessories position issue sound like a defective ignition switch.  The TBI pressure regulator could be the problem.  The fuel pump should not run on.  Check over the wiring to see if the previous owner by-passed any of the fuel pump wires and fuel pump wire routing.

Do you smell fuel or raw gasoline fumes?  Try the simpler items like the fuel filter, and if the engine runs fine outside of this issue, avoid parts replacing until you pinpoint the issue...


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Thanks Moses!! Sorry for the delayed reply, i think i have fixed my main stalling issue!

The issue appeared to be fixed after changing the crank shaft sensor. The old one was really gunked up and looked like it had never been replaced! No more stalling (yet) after idling 20 minutes and driving around a nearby parking lot. Idle was still rough though so today i replaced the fuel filter which was also pretty nasty looking and the rough Idle is all but cured! (knock on wood)

Quick question for you though, my fuel filter skid plate only had 1 screw holding it in and needless to say i lost the darn thing...Do you or anyone know the size of the screw and is it ok to drive it without the plate until i can get some?

I will look into the ignition switch, how would that affect the fuel pump though?

Thanks for your help!

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Tristan...The CPS is a common trouble point.  Congrats on the simpler fix.  My concern around the ignition switch was that the fuel pump wiring might be either bypassed or bypassing.  This would deliver continuous ignition current to the pump.  

If the pump shuts off as normal, the ignition switch and wiring are likely okay.  Drive the Jeep and see if you've resolved the problem...

Here is a PDF of the Mopar parts schematic and numbers for your fuel filter, guard and hardware.  There are no sizes offered, only part numbers.  Do a Google Search on the Mopar part numbers and see what the descriptions offer:  YJ Wrangler Fuel Filter and Guard.pdf.  

The cover screws look like common automotive body fasteners, available at any motor supply or even Lowe's (check the automotive hardware bins).


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