bigboy813

I've got this '89 Cherokee that I'm trying to fix. I just put in a new fuel pump, cap, and rotor to get it running.

It starts fine, idles great (no misses, smooth) for about 5-10 seconds, then begins to stumble badly, with a rattling sound coming from the cat (noise only during stumbling). After a few seconds of stumbling, if it doesn't stall, it will rev to about 2-3000RPMs for 1-2 seconds and return to a brief stumble and die. If you press the gas anywhere during its running time, it will stumble before revving, and then return to a stumble within a few seconds of revving (and usually die). Feathering the throttle sometimes helps. I found that revving it and holding it high RPMs (not letting it go below 2k by repeatedly flooring it) seems to keep it running a lot longer, but it eventually wont hold revs any more, stumbles and dies. Having a Renix system, I guess I can't check codes right?

I thought maybe the cat is the problem (it likely is no good), but could it REALLY cause this? There seems to be good fuel pressure, but since I don't have, nor can I afford, a fuel pressure gauge, I don't know for sure. I'm not even sure if fuel pressure would cause this, although it does seem possible. I've seen some strange effects on Powerstroke diesels from bad fuel pumps...

Anyways, any ideas? Any sensors I should check (and how)?

Also, it has a rubber piece sticking out of the front of the harmonic damper / engine pulley... ?

Thanks in advance

tjwalker

The rattling from the cat may be a clue. Rattling can be caused by the "heat shield" around the cat or from inside the cat, in which case the cat would need to be replaced.

You can easily test for a clogged exhaust (clogged cat) with a simple vacuum gauge. SEARCH the web for the procedure. Doing it this way, you don't have to temporarily remove the cat to verify if this is the problem or not.