Im new to this site and i was wondering if i could have some help. I just did a motor swap for my 1996 jeep grand Cherokee it had a 5.2 v8 in it so i put the same motor back in it. The timing is on and all cylinders are firing and its getting good fuel pressure and it idles fine, but when i go to drive it does good up until about 2000 rpm then it backfires and stutters. I have to let off the gas to get it to shift. I tried an iac and a new tps im just not sure, any suggestions would be helpful.

 

Any fault codes/ Check engine light? I would scan it even if the light isn't on.

I would go through and check all your grounds, and all the connectors you may have touched. as well as every vacuum line you can come across. Also any chance you had an opportunity to see the motor run before you installed it? Compression check? What is the fuel pressure reading at when it starts to act up? How did the ignition components look on the "new" motor.

 

Check the distributor shaft bushing for looseness. Once the shaft starts vibrating it can cause the spark to do all kinda nonsense.

 

I have a 1995 jeep grand Cherokee limited i put a 318 5.2 v8 in it from a 2000 ram. 1500

 

I hooked up all the grounds i have found, and no, I never saw the motor running, but it ran good for a few miles and then it started acting up. And i also got all new ignition components, distributor, distributor cap, and spark plugs.

 

Even on a V8, i thought that was more of a 4.0L problem.

i suppose it's possible that one or more sensors may be incompatible. You are swapping a pre obdII motor with one that is OBD II. even if the connectors plug in it's possible that the sensors may be calibrated differently. If it only starts to act up after the engine has had time to warm up for a few minutes I would start looking at oxygen sensors, a failed sensor will start to act up once the computer goes to closed loop and relies on the O2 for the AF mix.

 

It is more prevalent on distributors that run on an angle, but even Chevy small blocks are known for this problem.

 

Duly Noted