'96 XJ 4.0 149K miles - No Power

[Bob Langford]

No, it shifts ok. The article about knock (here: http://www.stanford.edu/~bmoses/knock.html
is interesting. Worth a read IMO.

 

[Bob Langford]

That Harrison OBDscan tool can graph engine ignition timing. That's one parameter I didn't look at when I had the log going. Next week, I'll get that hooked up again and see what that reveals. And I'll bite the bullet and buy a tankful of higher grade fuel.

 

[ezeman]

Bob

I have a 96 xj with over 160k. I have a problem, not exactly like yours, but a frustrating one none the less. My jeep would not rev past 3100 rpm. I replaced the MAP, CPS, TPS, cleaned TB, went through wiring, paid a mechanic 400$ to find a burnt out connector on the PCM, but the problem is still here, and it was intermittent, then it was permanent, intermittent, now permanent again. I cleaned ground connections, replaced coil, dist, rotor, plugs. I think I only have a few more sensors left to replace before I sell it and give up. If I think of anything else, I will pass it on, but I feel your frustration, trust me. I had issues with my 90, but nothing like this one.

eze

 

[Rambler100]

Please disregard this if it seems way off topic to you. Just joined and am investigating cooling problems. But I just has an experience with a honda accord with a lot of trips to a shop. The funny thing was it was a time/temperature thing. Short trips above 70 degree outside temperatures.
They diagnosed everything and finally when the condition was in effect we found it. This was a cooling fan running problem but what I am trying to relate is that the relay in the fuse compartment was hte problem. we had replaced all the sensors, thermostat, timer module. Anyway it is interesting to me that something solid state would act intemittently but when we thought though the conditions it was in fact a consistent problem and it was a relay.
Sorry if this doesn't apply but thought I would put it out there.

 

[Bob Langford]

Well, I ran the mail delivery yesterday with a tank of 89 octane. Outside temps were upper 60's but I had none of the crap this engine dished out to me in past 2 to 3 months. Last Monday it behaved poorly and temps were cool then too. I've pumped in 89 octane again this evening for mail run tomorrow. If I get another good day out there, I'm going to conclude that this engine has been experiencing 'knock'. That's spontaneous ignition of fuel on the compression stroke leaving very little combustion left for the power stroke. I think that's how I've read 'knock' described. Eze, this could be your problem, too. Try this next higher grade fuel.

 

[Bob Langford]

The Jeep ran good again today. Closing the book on this problem then. I'm going to take compression check in few days, will post readings here for info.

Thanks for all the good input. I forgot who suggested going to higher octane but you hit it right on !!