89 Cherokee random acceleration drop out

New here so please bare with me:shiver:
I have an 89 Cherokee 2Dr limited. 285,000 miles on it. With automatic trans, A/C, ABS, IE: all the bells and whistles.
I've had my share of issues, and have worked through them somehow. I, due to lack of use & funds, illiminated the A/C, & cruise control. Rebuilt the trans about 130K ago. Mostly it's been a great rig and don't plan to ever part with it!!!
Recently, at the most inopportune time and place the CPS died. Crawled out on a hook. Dealer was my closest shop and needed to get back to work next day.
So... CPS & ignition module replaced. When I picked it up & drove off it sputtered at idle, at acceleration, & at cruising and had no power. Tail pipe had the chug chug. Shop said ???
"You might have a fouled plug"
Possible... Long overdue. So I changed rotor, cap, plugs, wires, EGR, O2, because.... Long overdue. I did a mediocre clean of throttle body & IAC tip. Threw some sea foam in the tank and preyed the jeep preyer.

Rough and sluggish, cutting out on initial acceleration, pissing me off. Next day... Problem gone. Went to store later and problem back!!!! It has done this RANDOMLY for 4 days now.
Checked fuel pressure, normal readings, except at times, with regulator involved and not the gauge needle would radically fluctuate 3 psi either way up and down. The same with the manifold vacuum gauge needle.
By the way I only have about 14 in. of vacuum at idle. It slowly crawls up to about 18 then drops again. The revving exhaust restriction test seemed fine, but have already ordered a new magnaflow CAT to help keep the world spinning longer and make sure to have good exhaust pressure.
I've searched many threads & sites. Found some stuff, yet never a finished outcome on what problem was and what fixed it. I'm in this to the end.
Before I start going through all the checks on the cruisers list and treating my rig as well as its treated me, I was hoping for some wisdom. A baseline to start from as it were.
The vacuum needs, I suppose, to be addresses before I even get to sensors test. I'm finding it difficult to get clear knowledge on what it actually (the vacuum) should be. Each time I search I get threads on fuel pressure.
I would appreciate any wisdom.
This is long winded because I'm home and not out there this weekend.

Do a resistance check on your cps at the connector on the firewall and at the computer. There was also a more direct installation that dealerships could do to eliminate the c101 or whatever the harness disconnect connector is. I would also check for tightness on the cps at the bell housing.

Thanks for your thoughts. There isn't a c101 on my rig. The M/F plugs were bad so the tech kindly,clipped, soldered & shrink rapped the solders. I will check if the CPS is fastened securely. It's such a pain to get to, he might have overlooked that.

Click on this link and do Tips 1,3,4, and 5 before chasing too much other stuff.

The proper way to test the CPS is in Tip 7.

http://www.naxja.org/forum/showthread.php?t=1115935

When the CPS went out on my '89 2 door 4.0 it was with a thermal failure. Pouring cold water on the CPS got the engine started right up.
First replacement didn't fix the problem, so I checked by putting it in the oven @ 300 (?) deg. and checking with resistance meter.
Warmed up, no resistance. Cooled down, just fine.
Next one was just fine and worked for years.

With long enough extensions, short wobble extension and swivel socket you can reach the CPS from behind the transfer case. Put some grease in the socket to hold the bolt.
Mike

Thanks for the thoughts y'all. I'm working doubles all week so my first chance will be this weekend to go through the list. Fingers crossed that the solution is in the first few. The most I've been able to do so far is run a vacuum line inside and hook up a gauge to see what it's doing when the trouble starts. Sure seems it's all trouble from the gauge read. At idle in gear I'm at 14 inches. The needle bobbles between 14 down to 11 and back up. At times idle smooths out and gauge steadys out at 16 for a brief moment then back to bouncing around again. In low gear it goes up to 23. In drive bobbles 11-15. Stomp on it and "0". I don't think there is a blockage in the exhaust.
Is it possible the intake/exhaust gasket has failed between an intake & exhaust port. I had the beginning signs of exhaust flutter about a month age. I then checked & tightened all bolts. Last one next to firewall was gone. I think it was a stud. I replaced it at the time with a bolt.
I still plan to go down through the entire list to give the jeep a once over, I'm just curious if a compression test would give me some insight to a hidden vacuum/exhaust leak. I'm trying to plan ahead to make the most use of my day off work.
Thanks again.

Great idea using the vacuum gauge!!

Compression test wouldn't hurt.

Intake manifold bolts all snug?

Note from DJ

Vacuum Diagnostics
http://www.fordf150.net/howto/diagnoseengine.php

http://www.naxja.org/forum/showthread.php?t=1002311
Also some other vacuum interpretation sites that I found in my search:

http://www.therangerstation.com/Maga...acuumLeaks.htm

http://www.secondchancegarage.com/public/186.cfm
Look at #13 & 14
-------------
Conversion table psi to in Hg
2.04 inches Hg = 1 pound square inches (psi).
From http://www.engineeringtoolbox.com/pressure-units-converter-d_569.html

5 psi X 2.04 Hg = 10.2 Hg

Hectogram (Hg) is a unit of mass equal one hundred grams.
From http://en.wikipedia.org/wiki/Hg
-----------------------

My 88 sounded like it was hunting for some time turned out to be the vacuum harness, replaced both sides with a factory harness and was smooth agsin. I had a similar issue on an 87 and used a car quest one only to have to replace it a few weeks later. There is a lot of quality difference in the cost of those items was my experience.

Wow, lots of info. Thanks ! The one I really wanted to see was the second chance garage. The link opened, saw the write up, but the examples were not there( The ford link is great, think I'm second guessing myself with all that info. I'll try to video the gauge while running and see what y'all think. It's got a lot of miles, but I don't burn any oil, (I'm always on top of the oil changing). The sticking valve or lifter... Sometimes in the winter I get the tappit song till it warms up or I shift into low to loosen it up. No water in the oil or oil in the water. Intake leak.... Yep Cruiser...they're tight, just not sure if I got to them soon enough. The timing thing has me ???? I'm gonna cut up an old distributer cap & check exactly where rotor lands on TDC. I had a distributer changed three years ago. Now that I think of it... It has run odd since then. Just not bad enough to stress on it.
I'm kicking myself knowing I let someone else do what I could have done if I would have just take time, to make time.
On a good note the gremlins took a day off. Only one stall & no flat acceleration:sunshine:
I'll try the video and get back to y'all. Thanks much!!

Thinking about it. I'm not sure how to post a video, or if I'm allowed? Anyone got ideas how I can show y'all what the gauge reads while running?

Don't forget the fuel line inside the tank sometimes comes loose on the Renix

Well I started with the fuel system. Pumps good, new filter. Pressure regulator acting up so replaced it with only one I could find in my area without waiting a week, NAPA. Problems though. Can't get the fuel line to clip into the new regulator and split the o-ring. Heading to get new one by bus(. Any tricks out there to get the thing to go all the way in???
Tried oil, this is vexing me.

Just wanted to give a big thanks to crusier54...endless well of knowledge and kindness to share his wisdom with all of us.