heepinforChrist

recently had to swap my head out with a donor 89 4.0 head. got everything bolted back up and it runs poopy, and wants to shut off sometimes at idle. i had 3 codes 2 for the IAC and one for the engine temp sensor. i have to keep my foot on gas and brake to idle at a stop sign. it is ruff right from start up. no exhaust/intake leak i can see, ran fine before the head swap. i pulled the valve cover off and they all move fine looking, though i just looked at it in idle. there is also a weird burned oil/burned exhaust smell coming from somewhere but that could be unrelated( the mech put my brandnew exhaust pipe 1 in from the drain plug so guess what happens when i drain the oil) so far i have replaced the IAC, coolant temp sensor, temp sending unit(on back of manifold) seafoamed oil and vacuum lines through brake booster hose, cleaned IAC mounting surface and throttle body, changed oil(but not since adding seafoam like 25 miles ago) will do a comp check when i get a chance this weekend prob. any ideas for my next plan of action? o and after replacing all those sensors but before restarting the jeep i reset the ecu by grounding the pos for 30 sec. help

heepinforChrist

anyone??

Radi

The head is an 89, what year is the ECU and rest of the motor?

heepinforChrist

the jeep is a 96 the motor went like a year ago and had it swapped out with a 1990 no problems at all till now i swapped the head. 1990 engine 1989 head. if 6 years didnt mess with it would 1 year really be the diff, though i never thought of it. wouldnt the newer ecu just learn?

letinsh

You've crossed a pretty big boundary as far as the technology in the Jeep, but I don't understand how you didn't have a problem...
The 89/90 engine you have is designed to use the RENIX ecu. The 96 is the HO motor and is running the much more modern Chrysler ecu and has obd2.
The sensors and controls of the two systems are completely different, and usually you have to swap controls as well as motor whe crossing the 1991 model year.

I wonder how the engine ran so well before the head swap if the harness/computer were not swapped...

heepinforChrist

well it did not to be a jerk, it was fine. my new issues: replaced IAC, MAP, temp sending unit, coolant temp sensor, distributor, wires and plugs with oe. still the issues persist. i dont hink its spark but is it possible even though the head fit perfect on the block that the vacuum ports(if there even are any) dont line up correctly and are screwing up? not sure what else it could be. i guess i will check fuel pressure, i moved the intake man alot and it still had the fuel line that goes to the rail attached maybe i screwed that up somehow? i am also thinking just to take my old head(the one i drilled into) to a shop and have them weld a new stud in is this possible?

Gee oh Dee

For the most part any XJ motor can be used if you swap over EVERYTHING including sensors.

Chances are the OP missed something or messed something up when he did the head swap.

Gee oh Dee

My suggestion would be to do some actual diagnostics instead of just replacing any sensor you can reach. Test them to see if their bad first.

When its running 'poopy' try verifying GOOD spark and PROPER fuel pressure. Then move from there.

Also, try posting the EXACT codes that were found. The numbers for each...

cruiser54

Ain't no big deal. HO stands for Highly Overrated and if you've ever had the two side by side you would know there are no big differences.

crbnfibr

nice

JLK's XJ's

Kinda sounds like a vacuum leak...I assume new/correct head gasket with the head swap? All bolts torqued properly? Are you suddenly getting better mileage, or running hotter? That would be another sign. I'd check it with carb cleaner/WD-40/whatever while running, see if you can find a leak someplace.

heepinforChrist

i am assuming you meant PO when he did the head swap. it was a full engine replacement, i did the head swap and obviously screwed it up somehow. the codes wee 22,23,24,25 tested sensors they seemed ok but the codes were still there and when i replaced them they went away. it actually is running a little hotter, norm runs at 185ish now it passes the 200 mak a little, i just thout i needed to burp the rad and i replaced te coolant i have been losing from removing head, \disconnecting hoses etc with just water not coolant and water(i was going to address this later just dont have time or money now and i will pobably be losing more coolant in this process somehow) i will verify good spark and test fuel pressure. is it possible to hook a gauge up somewhere to see if i have good vacuum pressure and if its holding? or is the smoke test the only good way to test for vacuum leaks other then risking exploding my engine bay.