10 second hesitation, under load, upon cold start acceleration.. Why??

94_Country

New member
Ok fellas, I've got one for ya..
1994 Cherokee Country 4.0 4x4 Auto, 80k
I just bought this baby and I love it, but we've got a problem. For some background, I bought this car from it's original owner. He was pretty cool, had all the records, and gave me a good deal. Immediately after buying it however, I realized that I made a ridiculous rookie mistake in that I didn't check the records for the consistency of mileage accumulation. 80k is pretty low for a 15-year-old car to begin with, but it turns out that the first 65k were put on from 94-99 and the remaining 15k were put on between 99-09! Oh crap! 1500 miles a year?? At this point, I'm kind of hoping that the odometer was rolled back, but no such luck, those are the ORIGINAL miles! This poor car has been sitting for a decade! I'm flooded with morbid thoughts of having to replace every original part which is undoubtedly rusted, congealed, and/or cracked, and that it's just a matter of time before this ticking bomb goes off.
One day later....
I start the Jeep; it purrs
I put it in Drive, it keeps purring
I depress the accelerator and the car sputters
I quickly throw it in Neutral and it stabilizes
Dread washes over me; it's happening. Oy.
I put it in Drive, and depress the accelerator again
The car lurches forward and after about 10 feet, it stabilizes and drives perfectly for the remainder of my drive.

Basically, to this day, the car will only do this after it's been sitting for more than about 2 hours; enough time to completely cool off. Ambient temp does not affect the problem. If I run the car, stop it briefly (up to 2 hours), and then resume driving, the problem does not occur. The problem is magnified, however, depending on how long it has been sitting. I.E. Car sits 2 hours, acceleration stabilizes after 4 or so feet of lurching; Car sits 10 hours, acceleration stabilizes after 10 or so feet of lurching.

~Day one; Replaced original spark plug wires, cap and rotor; checked spark plugs
No change. GRR :x
~Day two; Replaced TPS sensor
No change. GRRR :x
~Day three; Replaced MAP sensor
No change; GRRRR :x
~Day four; I realized that the A/C and Cruise are mysteriously inop as well, so I'm thinking vacuum issue! Hmmm could it be?
After reviewing the service files, I saw that the vacuum system had been looked at recently. It checked out fine, but then I realized that maybe one of the wonderful mechanics cracked a brittle hose somewhere and the system was, in fact, losing vacuum.
~Day five; I checked the vacuum system and found a cracked hose attached to the evap canister, replaced it, and LO! The A/C and Cruise work again!
But... No change in the hesitation upon cold acceleration!!! GRRRRRRRR :x

I've not ruled out a vacuum leak but I cannot, for the life of me, find one.
I also think it may be a fuel delivery issue, but that doesn't seem logical based on the type of consistency of the problem. It seems like a sensor/slow vacuum leak issue. I may be wrong.

Help me please? :roll:
 
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