Motor Question

[etaucher]

I bought a Jeep Cherokee off someones friend here on Pa Jeeps, the Jeep is a 1994, and I was looking at the motor yesterday, and took notice that the Manufacture date on the motor sticker says the year is 1996. Now I no, no one is going to know if the motor was replaced or not, but I was wondering if maybe I was reading the sticker wrong. I will take a picture of it later today and post it up.

[etaucher]

Ok, heres the picture.

[Rick_Bear]

Yeah, you're reading it wrong.

4 9 9 6 (Read it backwards)
      ^             ^
   Year       Day of Year

[etaucher]

O! Ok, thanks for helping me read it right.

[etaucher]

Alright, I got a problem with my motor. This morning I was driving it, I turned into an empty parking lot to go pee (LOL), and when I pulled into the lot my Jeep stalled, I didn't think nothing of it, (maybe I stalled it). So I go pee, get back in and start it, and the motor kinda dogs starting, the RPMS drop down to about 500, it sputters abit then the RPMS go back up to 1,000 and my check engine light turns on. I give it gas and it dogs around 2,500 - 3,000 RPMS. And it does this everytime I start the Jeep. When I drive it, it seems like I have a lack of power.

I checked over the motor, it has the right about oil, all my plugs and wires are good, I checked all the other sensor plugs. And everything seems to be fine. But I just don't no whats wrong. Im getting ready to go to Auto Zone, because they offer Free Check Engine light test. I will let everyone know what Auto Zone said.

[etaucher]

Auto Zone said it was my Map Sensor, so I bought a new Map Sensor. That didn't fix the problem, then it sounded like I had a bad miss. So I bought plug wires, that didn't fix the problem, so I bought spark plugs, that didn't fix the problem. So we checked the codes again, and it threw another Map Sensor code. So we ordered another Map Sensor, it will be in today at 5:30pm. So I will go back at 5:30 and get it, and see if that fixes the problem. If not, Im stumped. And I will be playing the guessing game.

[Davew]

You need to check the fuel pressure. You could try a new fuel filter but it sounds as if the fuel pump is going bad. You got a MAP sensor code due to it running poorly and engine not creating enough vacuum

[etaucher]

I bought a TPS, and that didn't fix the problem. Tomorrow Im going to replace the Cap and Rotor. We pulled them today, and they are shot.

[etaucher]

Replaced the Cap and Rotor, and that didn't fix the problem. So I went to the junk yard and pulled a few sensors off a wrecked XJ. And turns out it was the sensor right next to the TPS that was the problem. It still has a bit of a rough start, (sounds like a vacuum leak) but after a few seconds it ideas normal.

[etaucher]

Another question, Im looking at a 1988 Jeep Cherokee with the 4.0 Renix? Motor, as a parts car, can I use the motor out of the 88 in my 94?

[Davew]

The motor itself will bolt in but the fuel management system is different, the cylinder head is not the same but will swap between short blocks. 

[etaucher]

So would I take the head off the 94 and put it on the 88 block?

[hillbilly]

yes but the older 4.0 are rated at less torque and hp along with a diff. intake design.

[etaucher]

I figured out what was wrong with my motor, I had a vacuum leak. The line that goes to my map sensor was shot. A 10 dollar hose fixed the problem. Now it runs great.