ZooKeeper

New here although I have been looking at others posts to try to fix my issue. Sorry for the long post in advanced, but I figure being detailed is better.

I have a 1988 Cherokee Chief 4x4 Auto 4.0 inline six.
I bought this Chief in the Caribbean (it had sat for 3+ years) with the intention to fix it up and have a 4x4 down there. Plans changed and I moved back to the US and shipped the Chief back.
Once it arrived, I took it to the mechanics and had the following done:

New wires, cap and rotor.
New plugs
New injectors
New fuel filter
New fuel pump

When I got it back, I drove for about 3 days and the radiator crapped out, overheating the engine.

I bought a Reman 4.0 (ATK) 909MX12 and swapped out the engine.
Installed new with reman engine:
Harmonic Balancer
Radiator
Distributor
Fuel filter
Coolant Temp Sensor
TPS (adjusted)
O2 Sensor
CPS
Ignition Coil
Ignition Module
EGR Valve (although I wonder if I need this?)
Air Filter
Oil Filter
Oil Pressure Sensor (?)

All vacuum lines installed correctly, no vacuum leaks.

When all was ready, started the engine. After 3-4 cranks, she purred!!!!
Idled great!
But as soon as I added throttle, she bogged down, popping thru the intake and an occasional backfire.

Cruiser54's pink link tips done:
1,2,3,4,5,7,8,9,10,11,12,13,18,27

Still having the same issue. Any ideas or direction will be greatly appreciated.

67 GMC

Check fuel pressure at the rail during idle and when applying throttle.

ZooKeeper

Just checked the fuel pressure. 31psi at idle - 39 psi with the vacuum to FPR removed - applying throttle raises the psi from 31 up back down to 31 when released. Still bogs down.

cruiser54

Did you adjust the TPS on the Engine side? Flat connector?

Have you double checked the distributor indexing?

ZooKeeper

Thanks for looking at this.
Yes on both. TPS A&B measured 4.89, adjusted to .83.
Distributor indexing as per your write up.

cruiser54

Acts like a fuel volume issue or possibly a secondary ignition issue.

ZooKeeper

Would the Coolant Temp sensor be a possible cause for the fuel volume issue?

Cherokee_of_Tennessee

You may want to read thru my thread here:
https://www.cherokeeforum.com/f2/hes...3/#post3002995

I had a very similar issue. Replaced nearly everything involved with ignition, then finally the dealer caught the fuel pump cutting out intermittently during a distributor test. I know you just put in a new fuel pump, but it is not un-common for them to be defective straight out of the box. Dealer also said the XJ's are very sensitive to sensor components. Some of the aftermarket sensors don't work very well. Hope this helps.

cruiser54

Nah. It can be tested as can the IAT.

MontanaXJer

I had a similar issue a few years back. Turned out that the rubber fuel hoses coming from the tank were dry rotted allowing pressure to bleed off under load, which was causing my engine to hesitate and even backfire in the intake. I replaced both rubber fuel lines coming out of the tank and it resolved my issue. Ethanol gas wreaks havoc on these lines. It would be worth your time to inspect all of your fuel lines to see what they look like.

67 GMC

What brand of fuel pump did you put in? I had a similar issue with a bad pump. Put in a Carter. Lasted a few months and same problem. Put in a Bosch and no problems since. Mine would bog down and if you floored it you would hear the backfire in the intake.

cruiser54

MontanaXJer and 67 GMC may be on to something.

ZooKeeper

Happy New Year to all.

I will check the fuel lines. Thanks MontanaXJer

I bought an Airtex Fuel Pump about 2 years ago. I replaced it with a Precision Fuel Pump. This one registers the correct psi when idling and applying throttle, which leads me to believe its good.

cruiser54

Can you even drive it?

ZooKeeper

No. As soon as the throttle is touched, the bogging starts. More throttle, then pops thru intake with an occasional exhaust backfire.