engine trouble possibly sensor?

my 97 cherokee 4.0 is having major problems after reading the self diagnosis codes i have replaced the TPS, CPS, MAP, o2 (downstream one), and VSS sensor along with new spark plugs and wires, but it still runs bad so heres how its running, at cold startup it runs perfect idles nice and drives nice til i hit 5th gear, then its nice and warmed up and it loses all power and pops and pings in the engine area like its backfireing only when warm, with all the new sensors replaced there is no check engine light. so im sittin in my driveway holding it around 2500 rpms for like 10 mins or less hoping it would just clear up but it like pullses or something and then suddenly i notice smoke inside under the carpet the muffler got way to hot obviously , does anybody know if its distributor related? oh yeah if i drive it with the pedal to floor it seems fine but only all the way to the ground not half way all the way... please someone help!

You could try rotating the distributor a little bit. If you do this, mark where it is now first. At the firing point (something like 14 degrees BTDC, the rotor needs to line up with the correct post inside the cap. You should search a little for how to do this on an XJ. My 2000 is distributorless.

does anybody know if its worth getting a new distributor sync pickup? in other words whats the symptoms of a bad sync pickup?

you can test the sensor. im not sure what wires it is but i should show a pulsing voltage of about .5V to 5Vish. if the CMP was completely bad though your jeep wouldnt even start. its obviously running extremely rich if its making your cat that hot. also worth checking could be the coil. they can often start malfuctioning after they get a little heat in them. other than that id get a scanner and start looking at what various sensors are saying and go from there.

What codes did you get? Blindly throwing parts at it can get real expensive. A better investment is a $10 meter and a little time to learn how to test sensors first.

The downstream O2 sensor doesn't affect how the engine runs. The upstream O2 sensor isn't really used until the engine is warmed up a bit, and that if its bad the engine will start running like crap when the computer tries to start using it. The computer also doesn't use the O2 sensor when you're at wide open throttle. You might try just unplugging the O2 upstream sensor (up by the engine) and see if it runs better. It will throw a check engine light, but it will ignore that input and make its best guess.

Also agree that a bad coil is a possibility, even if it doesn't quite fit the symptom of running okay at WOT.

sounds to me like the upstream 02 sensor. When mine went bad on my 98 it ran like hell, total loss of power, bucking/surging, backfiring in the manifold. Replaced it and good as new.

hmmm i might have to try that upstream sensor than, and oh yeah i wasnt just throwing parts at it 91-97 has that self diagnosis feature where ya flip the key on off 5 times and it gives you a number of which sensor is bad and i actually took it to a shop to have a professional use theyre sensor tester and it came back with the same sensors that might jeep already told me, so that was a waste of 35 dollars
anyway i will check the coil and upstream o2 andd see what i come up with

If its a 97 it has obd2. The fault codes don't mean the sensors are bad. Its in Indicator of where the problem is. Yes sensors go bad but they also have need correct power and ground and signal voltage. I had a problem with my 98 stumbling and rough running. It was giving p codes for o2 sensor heaters. Turned out to be a broken ground. What P codes did you have stored.

The rub with trusting the onboard diagnostics is that its not totally foolproof. It is a good starting point. For many things, such as a bad TPS sensor its usually right although it is very easy to do a quick meter check on the TPS first. For some things it can give you a misleading trouble code like o2 sensor too lean when its really a fuel pump or even a bad coil. Or perhaps a bad MAP sensor when its really just the vacumn line is split.

huge success it was just the upstream o2 sensor i feel like a retard, it was the one i didnt check but now i know, thank you all for the assistance i almost went to an actual mechanic

glad to help. that pesky 02 sensor can cause a world of problems when it goes bad.