Dallas Baer

Hey everyone! This is my first post to this forum! So I will try to include as much info as I can. Yes I have searched multiple threads and all over Google and I just feel like I'm running in circles.

So this is my third Cherokee. (First Chrysler body style) 1st was a 92 non renix. 2nd was a 91 non renix.(this one was a major donor to the 3rd) 3rd is a 98 complete chrysler.
This 98 is a base model 4.0 manual 5 speed.
When I bought it it had a heat soak/vapor lock issue. Would always take like 10 seconds of cranking after the motor was hot before it would idle.
I did new plugs, checked the gap, oil change, 15w-40 Rotella diesel + filter. And I swapped the known strong working injectors from the 91 to this one.
For the most part the heat soak and long cranking is gone. But now in the mornings, essentially a cold start. (I live in Arizona so the mornings right now are like 75-80 degrees. It takes a few seconds for it to turn over and idle, but then it's rough and stumbles and putters. Feels like it's close to dying and doesn't take very kindly to accelerator input. Once it's driven through the neighborhood it's fine. Runs and drives strong and idles perfect at a light for the rest of the day. It's only that first start of the day.
It almost feels like a misfire but there's never any cel.

Dash says 260k+ but due to the original color being blue and the whole engine bay has been resprayed black I'm positive it's not the original motor or has been rebuilt.

IAC and throttle body has been cleaned and probed.

CCKen

I had experience with sort of the same issue - rough running at start up/drive away. It turned out to be a defective upstream Oxygen Sensor.


Side bar - I would recommend Shell Rotella T6 5W-40, not 15W.

Dallas Baer

Where would I find an upstream oxygen sensor. I'm only used to one OBD2 vehicle and it's a Honda and it's running an OBD1 computer so upstream and downstream don't make much sense to me

robertj

This was my first thought too, but it should throw a code eventually.

Upstream is before the catalytic converter.

97grand4.0

loose dizzy shaft, ckps, cps, iat, cts, batt/ambient temp sender, tps, thermostat, fouled plugs from all the above and not hitting closed loop