Jeep Strokers

just built a 4.6L for my wrangler to replace 4.2L. robbed the 4.0L and wiring harness out of a 93 grand cherokee. motor starts up and idles fine with slight miss. when i drive it down the road and punch it, it bearly revs up, just feels like it has no power? the 4.2L had more power... i know the timing is right, 150 psi, 35-40 psi of fuel pressure. the 4.6L has comp cam x4250h-13, 2002 tj head and intake manifold w/ 24lb ford injectors, also using pcm out of 93 cherokee to bypass the grand cherokee's sercurity system, everything else is stock. all the sensors are functioning properly, the only thing ive found wrong so far is the adaptive memory, the fuel % is reading -5.2%. can't figure out why though??? please help! miss driving my jeep and running out of summer time! thanks!

Well, the injectors could be just a tad large, judging by the -5% fuel trim, which isn't abnormal. That wouldn't cause the issue are having. Have you checked your TPS and MAP sensors? Are you sure that your distributor is indexed 100% correctly? The wiring harness is from a 93 ZJ and the PCM is from a 93 XJ? Are you sure the pins in the plugs on the PCM are correct for the XJ PCM?

What about transmission? Are you running a manual? If it is an auto then the 93 ZJ may have had and AW4 or a 42RE. If the PCM came out of a ZJ with the 42RE I don't know what effect that would have...

i figured the fuel trip should atleast been in the positive numbers? i havent messed with fuel trim alot, so im not 100%? yeah tps and map are all fine. distributor is correct. and i checked the pinouts in both the connectors(both are the same). im running a manual trans.

A negative fuel trim means it is pulling fuel out based on what the O2 sensors see, so with larger injectors it would pull fuel out. That is normal though. What about your coil?

Is the ZJ PCM from a manual ZJ?

i put the stock injectors back in, and that made no difference. thought mabey the 24lbers might have been over fueling. it has the stock coil on it..it zapped me once, it hurt. so i assume the spark is hot enough. haha im using a xj pcm, it had a auto and the wiring harness was out of a auto zj.

Hi there. IMHO, I too agree that it is not the issue of injectors. +/- 5% would not cause that, especially if it is the long term adaptives. Look somewhere else. Double-check the distributor orientation, do you have a catalytic converter ?
I don't have the specs for 93 models, but how is the fuel pressure at WOT?
Also the current fuel delivery system is a returnless type, what was it supposed to be for 1993.
One more thing, but it maybe just me, I don't get it sometimes: You used an older Grand Cherokee ZJ PCM. I think all ZJ's were produced with automatic transmission, Right? 'cause the PCM in either cases then controls all transmission functions (42RE if behind 4.0 L6, or 44RE if behind 5.2 ). Are any DTC's thrown? Could you shed more light on your vehicle specs and the donor vehicle.

hatem61 wrote: You used an older Grand Cherokee ZJ PCM. I think all ZJ's were produced with automatic transmission, Right? 'cause the PCM in either cases then controls all transmission functions (42RE if behind 4.0 L6, or 44RE if behind 5.2 ). Are any DTC's thrown? Could you shed more light on your vehicle specs and the donor vehicle.

He used a XJ PCM from an auto, and a ZJ wiring harness. That could possibly be part of his problem.

im running no converter. fuel pressure is 35 and about 40 when i rev it. and the only code set is for the a/c relay... mabey i just need to get a zj pcm without a security system?

No... I don't think at all it has with the security system of the PCM.
Start again at the very basics first
Good luck

It isn't a security issue. The security will let you start it, then run for like 4 seconds then die.

I think your problem is something with your wiring harness, a PCM from a different vehicle, and lack of an automatic transmission on an auto PCM. I would start looking at what the PCM is actually seeing if you can.

i dont konw, i just won a 93 wrangler engine harness off ebay, so im find a pcm for that, and see what happens...

index the distributor/cam sensor with the toothpick method... your problem will go away... 100% sure that's the problem it almost always is on fresh startups.

toothpick method???

1bolt wrote:index the distributor/cam sensor with the toothpick method... your problem will go away... 100% sure that's the problem it almost always is on fresh startups.

This is what indexing the cam sensor is.

From All DATA



3. Temporarily install a toothpick or similar tool through access hole at side of oil pump drive housing. Align toothpick into mating hole on pulse ring.
4. Install oil pump drive into engine while aligning into slot on oil pump. Rotate oil pump drive back to its original position and install hold-down clamp and bolt. Finger tighten bolt. Do not do a final tightening of bolt at this time.
5. If engine crankshaft or camshaft has been rotated, such as during engine tear-down, CMP sensor relationship must be reestablished.

That illustration shows the toothpick going horizontal through the body instead of vertical through the base. There is a hole on the pulse ring right at the edge of the shutter and a hole in the base of the dizzy body--these are the two that need aligning.