After scouring the site for tips on similar issues that I'm having, nothing has worked to resurrect my cherokee.

Symptoms: Will crank stone cold no problem. Will run at a perfect idle until about the time the thermostat opens. At that point it will randomly start bucking stalling and ultimately die. This usually takes around 3-5 minutes of idling. Faster if its being driven. After it stalls out, it will turn over and try to crank but if it does it almost immediately stalls out again and won't crank back normally until bone cold.

Already tried:
All of Cruisers list other than 2 or 3 mods
New TPS
New CPS
New ECU
New vacuum lines
New IAC Valve
New MAP Sensor
New MAT Sensor
New Engine Coolant Sensor
New O2 Sensor
Everything sensor wise that is not new has been properly tested
New plugs and wires

This thing is 50 dollaring me to death and I'm determined to get it running again. Any ideas on what to check/replace next?

 

I cant help you, but I feel your pain and can relate about the 50 dollering to death...lol
Good luck with your problem buddy..

 

Haha it's a labor of love

 

It sounds like you're well informed, but just in case, if your '87 is like my '89, it has two coolant temp sensors. One for the dash gauge/light, one for the ECU. Did you replace the correct one?

 

Back to basics is when I get stumped. Got spark at plugs when dead ? Fuel pressure cold and then dead. Maybe some sensor testing when cold then when dead ?

 

My coolant temp sensor is on the thermostat housing. Other models are on the side of the block. I replaced the correct one.

The temp sending unit is toward the back of the valve cover and should only be for the idiot light.

 

I do have spark when it dies.

Don't have a way to test fuel pressure. I guess I could rent a gauge.

Thing is if you hold the throttle to 2500 rpm it was run indefinitely. Seems to me if it were a fuel pump/ valve issue it wouldn't be able to do that?

 

Do you do Tips 5 and 6?

 

I do not trust testing of sensors.

 

And why is that?

 

I pulled back the split loom to visually inspect the splices and everything looked good and secure.

I also performed the ohms test and had on average .1 resistance between the various connectors and the negative battery terminal.

 

Perfect. You're doing all the right things.

When it cranks and won't start, and has spark, do you have a pulse at the injector plugs?

Don't forget that the fuel pump ballast resistor can heat up and fail or have lousy connections.

Still got the c101? If so, wiggle that while craning after it dies and see if that helps.

 

Check to see if the intake manifold bolts are loose. Usually that results in an increased idle when the system goes to closed loop but it is worth checking anyway. And if you do need to tighten them don't go all Armstrong on them. You don't want to snap any off. Best of luck Bro!

 

I do have pulse at all 6 injectors.

Where is this ballast located?

Yes the c101 is intact and cleaned spotless. This issue first happened after my failed attempt at bypassing the C101. Got some wires mixed up and fried the ECU. Found a complete harness at the boneyard from an 88 that was in very good condition and put it in along with a new ECU.

I have also replaced the EGR valve and relay assembly. Forgot to mention that.

 

I'm pretty certain the engine is leaning out. If it was a manifold issue it should be high idle not low right?

Nevertheless I have checked the manifold bolts and vacuum with the ether test. Everything is air tight. I think I think it has a very minor exhaust leak in the exhaust manifold but I've been told that should make it run rich not lean out?