I guess the fun never stops when you modify an engine outside of what it was designed for.

First off, I’ve had this issue ever since I started driving my Jeep after the motor was put back in, but I thought it was just the computer trying to adjust to the camshaft, but it’s obviously not that since it’s still happening after 700 miles.

Okay. What’s going on is that if I accelerate from idle in 1st, there’s no power until about 2.2k, and then it takes off like a bat out of hell, and then does it again when I shift to 2nd and so on. If I’m in 4th or 5th and accelerate rapidly, the power is there, but only in the lower gears with a lot of throttle does it not put any power down. The best way I can describe it is that it feels like I have a turbo.

Im not sure if it’s the TPS, because it doesn’t happen in higher gears with the same throttle, only in lower gears. It also happens as I’m warming up, and when I’m warmed up. If it’s a cold start, this thing fricken takes off around that RPM range, but once it starts to warm up, the issue starts happening.

I don’t know if the computer is having trouble compensating for the cam when it’s warming up, or if I’m just outside of the range of the computer because of this cam, or if there’s some restriction.

I know I’ve heard of some people “modifying” the MAP sensor when running high lift cams, but the only person I know of that “modified” the MAP sensor on a 2.5 Jeep was Dusty, but I can’t find it.

If anyone has any ideas, please shoot them my way. I’m sure this is because I’ve put a decent sized cam in, cause this wasn’t happening before I rebuilt the engine

 

Likely too much cam. You can change it without removing the head. Advance the cam timing?

You could try advancing your CPS.

TPS can be checked but just for fun, unplug it and drive the Jeep.

 

Learn to downshift.

 

I found the issue.

I’m guessing the O2 sensor can’t keep up with the exhaust flow, since there’s more of it with this new cam. I unplugged the O2 and it reverts to the stock fueling table and it runs a lot better when it’s warm. I figured since it starts acting weird when it’s warm, it has to do with the O2, and sure enough, that O2 can’t keep up.

Is there any way I can get an O2 that’s more “tuned” to higher exhaust flow?

 

What brand do you have installed now? Probe contamination will hinder the sensor.

 

A quick look at Rock Auto shows the 1995 2.5 and 4 l use the same O2 sensor. I suspect the 4l probably has more exhaust flow than your hacked up 2.5. maybe you should just try a new O2 sensor.

 

Sorry for the late reply.

The only sensor that is the same between the 4.0 and the 2.5 is the NTK sensor, which happens to be the sensor I bought some time ago. I’m going to try a new sensor, unsure of what brand. But I do know that the Jeep is much happier without the oxygen sensor plugged in, so for now, no O2 works just fine

 

It was not the oxygen sensor.

After I swapped in a 96 PCM, I plugged the O2 back in to see my fuel trims, and at idle, they are pretty normal, around the 5-10% range. But, while driving, they shoot up to the high 30’s, which means that my cam is causing the computer to freak out, so it dumps more fuel and retards the spark, making my Jeep really slow all the time.

And for anyone wondering, the OBD1 computer does not even touch the oxygen sensor until it’s warm, but the OBD2 computer uses the O2 to calculate fuel trims, which would affect open loop and closed loop operation.

The more you know

 

why don't you swap to a milder cam?