87 jeep cherokee stall/ no start problem

Had this xj for over a year now as my daily driver. It is a 4.0 in-line 6 engine with 4wd.

This summer I have encountered a stalling problem: it runs well while driving, no problem, but as soon as I decelerate to a stop (in drive, foot on brake, such as a red light or stop sign), it will stall out. 75% of the time it will start right back up, and 25% it will not. The engine kicks/turns over fine, and I have full power from the battery, but I cannot get spark. I will wait 20 min or so and it will start up again. My temp gauge also reads normal, so I know the engine is not overheating.

Stall is also triggered sometimes when hitting a speed bump or train tracks, but if I punch the gas at the same time as hitting the bump, it will not stall. I have also figured out a trick for red lights: if I put it in Park and continue to give it it gas, it will not stall.

I have replaced the fuel pump and the fuel filter last week, IAC is brand new, and my engine is brand new as of last summer.

Sometimes when I haven’t been driving it, and I try to start it mid-day, it will not start up (same as before, The engine kicks/turns over fine, and I have full power from the battery, but I cannot get spark). I have pondered the possibility of “heat soak” causing my fuel injectors to seize up, because it is common in the 4.0 xj, and because it seems to worsen during peak heat (95 degrees). But, I have never heard of heat soak causing so many problems.

Any thoughts would be helpful!

The problem could be caused by a dirty/defective Idle Air Control valve.

https://www.rockauto.com/en/catalog/jeep,1987,cherokee,4.0l+242cid+l6,1179716,fuel+&+air,idle+air+control+(iac)+valve,6072

Tester

I’ve considered this, but the one I have is new.

Is the problem only when the brakes are applied?

Yep or probably, more specifically, when I am not giving it gas.

Could it be fuel delivery? Filter? Pump? Clogged gas tank venting system?

When this happens, pull over and take off the gas cap. If there’s a large vacuum, it could be something plugged in the tank venting system. If it’s easy to reproduce, try doing that with the cap a bit loose.

This is fuel injected, right? I doubt it’s heat soak.

Replaced the fuel pump and filter last week, do you think it could be another component of that system? fuel rail or injectors maybe? I’ll try that out and check for vacuum.

One way to check - hook up a fuel pressure gauge, see if there are any issues. Just make sure the hose ends are secure.

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