I have a 88 jeep Cherokee 4.0 auto

Ok so i blew the motor in my jeep. Replaced it with a known running 4.0, Unfortunately after i got the motor in, i was trying to crank it and it sprung a fuel leak at the same time it backfired through intake and caught on fire... just for less than 10 seconds.

The only noticeable damage was burnt wiring harness. I had an extra one so i swapped it all over, fixed other wires and vacuum lines that were damaged. I got it too crank, but the idle is HORRIBLE... Sounds like it had a aggressive cam in it. I cant tell if its missing or not, just sounds rough. Whole motor jumps and shakes. ALSO when i give it throttle it just bogs down and backfires through intake and exhaust I THINK.

So far i have swapped out TPS, IAC, DIZZY, PLUGS, WIRES, INJECTORS, Got a new MAF sensor. Vacuum on that is good. Checked all grounds and cleaned them up.

This motor sat in a barn for a while before I installed it, A while meaning 6 months or so, I ran seafoam through it, pulled valve cover cleaned it up pretty good.

The CPS wouldnt cause this would it? Usually they work or dont work i think.
EGR make it un drivable?
o2 sensors make it this bad?
Knock sensor make it act this bad?

After the fire i assumed i would have blown fuses due to electrical issues but NO fuses were blown.. ANY HELP would be appreciated.. Thanks so much

 

sounds like the timing is out have you loosened the distributor hold down bolt and rotated the distributor while its running to see if it comes around?

 

I have Fooled with the timing 3 times. I cut the Hold down tab off, Adjusted to TDC using the Thumb in hole method until i felt air push my thumb. Stuck a soft end rod into cyl #1 and hand cranked until i found TDC. Dizzy rotor lines up with #1 Plus i can adjust it because i removed the tab. Dont matter if i turn dizzy or not, it runs the same to a point, until i get too far and it dies.

 

Stupid question. Have you checked the firing order of the plug wires?

 

Yea I have numerous times.

My only thoughts is. Timing chain slipped or cam is worn. Motor ran before it was put in barn tho.

 

I would do a compression test.

 

This probably isn't it if you're not throwing any codes, but mine did this when the O2 sensor 15amp fuse was blown under the hood.
https://www.cherokeeforum.com/f2/o2-...ay-fuse-65485/
I have no idea if this even applies to an 88, but if it does, there's something to check.

 

Another possibity. wires coming out of distribitor. There are 3 wires together that could have gotten pinched by the cap. I had it happen to me and had the same symptoms.

Could also be an injector issue. If one of them were stuck open it would sound like that. It would run extremely rich as well. If its smoking blue then try to check them. With it running pull one wire off at a time. If it runs worse then that injector isn't the problem. If u pull one that makes no change probably stuck open.

There are many possibilities. I just tried to give you a couple out of the box fixes. I had both of these happen to me at some point.

 

Holey cow. You might read over Cruisers stuff in the link in my signature. I can check the AC output from the CPS in the time it takes to tie my shoes. Make sure the MAP tube is flawless to the TB. Try to put the dizy back where it goes. The books are wrong, #1 is at 5:00 viewed from the side.

(it should run fine with the wires to the dizy unplugged)(it has no light, and no computer memory)

Cruiser will be up early in the AM. Likely the c-101 connector will get mentioned! There is some more to start with....

 

What year motor did you swap in? Do you have good fuel pressure? Lean mix will backfire and run rough. Agreed on the compression test too.

 

Excellent point. Post 90 uses a bunch of different stuff. May well be the torque plate being one. (see HO/Renix swap)

 

Fuel pressure reads 40 psi on idle. I replaced injectors with known good ones (they are used but worked two weeks prior in my old motor)

The motor i swapped came complete, Looked just like the one i pulled out. Same sensors and connections. Same parts. THE ONLY DIFFERENCE I NOTICED BETWEEN THE TWO was the wiring harness. My old harness is what im using the CPS sensor plugs in the wiring harness that runs after the c101 connector. The new harness that burned up had the CPS sensor running through the connector. I think driver side of plug LINE b the second 2 wires arnt there. CPS is fine the way it is, Im using original harness, C101 is clean...

Re used old oxygen sensor from old motor that worked fine before it blew.
dizzy is free of any pinched wires
fuel pressure 40 psi
grounds clean
re used tps iac injectors dizzy
NEW plugs and wires

When motor is running it dont smoke. I havnt done a COMP test cuz i have seen motor run prior to my swap.

Fried ECU form the fire and maybe got shorted out??
Timing Jumped?

 

What year motor did you swap in? If HO, did you do it like this?

Cruiser’s HO into Renix Swap

This swap is easier than some will lead you to believe, generally those who have never done it. Those of us who have done it, like myself, will share with you the things that need to be done for a successful swap. Just think of it as swapping in a long block.

The HO and Renix have some differences but none that can’t be overcome very easily.

Any HO engine from an XJ or ZJ through 1999 can be used. One running change was that the rear of the head was no longer drilled and tapped for the temperature gauge sender beginning in the 96 model year. The sender can be relocated to the threaded hole in the thermostat housing taken from the HO engine. You’ll have to extend the wire to that location. Some brave souls even drill and tap the HO head for the sender.

You will be using the intake and exhaust manifolds from your Renix, along with all your sensors and wiring. Since the intake ports of the HO are slightly different, you use the Renix gasket. Exhaust ports are identical.

You will need to use your Renix distributor as it is different than the HO because they use different fuel management systems. The flywheel or flexplate from the Renix must be used so your CPS gets the correct signals. The valve cover from the Renix allows you to keep your CCV system intact and requires no modifications.

The HO block will have a plug in the coolant galley on the driver’s side of the block, closest to the front, which needs to be removed so your Coolant Temp Sensor can be installed in it’s place just as it is on the Renix. It requires a 5/16" square drive or a modified 3/8" drive that has been ground down to fit. Do this before installing the engine.

As for the knock sensor, which is located just above the oil pan on the driver’s side of the engine about mid way, all the blocks I’ve seen are threaded for it. If not, I’ve heard they may be drilled but not tapped. Tap the hole if that’s the case.

　

Revised 03/28/13

　

 

what are visual differences between HO and Renix 4.0s

All the plugs have been used and i see no sensors that arnt plugged in.

We may have posted at same time, I added some updates above your post.

 

Renix has a 3 bolt throttle body and HO has a 4 bolt one.