Engine Power Loss

I have tried all I know and I'm STUMPED !!!!!


I have a feeling that the problem has to do with the timing advance.

My Jeeps engine runs up to speed, but even the smallest hill or rise in the road will reduce my speeds, that is when the transmission downshifts (which only helps minimal).
My gas mileage is trashed (12 mpg with a tail wind), which use to be about 20 mpg. The transmission will up shift and down shift ok, but like I said already the slightest hill or upgrade in the road and she boggs down in speed.

Can some help me figure this one out?????

Can someone explain the therory of electonic timing advance?? I took apart my distributor to see if there was something dirty or mis-aligned but can't see how the timing is advanced. I bolts in with no way to adjust the distributor to change the timing on that either. It has a new TPS and Crank sensor

If you have any questions that maybe I missed on e-mail me direct at: peterbuilt_6969 at yahoo.com

I really need to figure this problem out soon because a planned a vacation (with a 4x4 group) to the desert the end of April and need an operating XJ...


HELP...

When was the last time you did a major tune up on it? The electronic timing advance on the xj's is controlled by the computer thus taking away our ability to advance or retard the timing like you used to be able to do.

After the tuneup, consider checking your O2 sensor; there are numerous posts about an O2 sensor failing and causing bad mileage.

WHo put in the TPS? Was it adjusted properly? Were you having this problem befor the TPS/CPS change?

I have only owned the Jeep for about 18 months now.

A tune-up was conducted right after purchase, TPS replaced (and set IAW specs), Crank sensor replaced, O2 sensor replaced and right after the tune-up the engine ran fine. The problems started about 3-4000 miles after the tune-up. This is why I started looking into this problem. When I start from a stop the engine ramps up fine. I really notice the problem after the transmission shifts to third and fourth (overdrive ??) gears.

When in third (or fouth) and a small upgrade or hill approach I try to increase the throttle to make up, but there is really no changes (decreased speeds only); until the transmissiondown shifts and then there is only a minimal increase. I will recheck my TPS again, but I don't think that that is it.

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As for the advance question. On an older vacuum type engine you can see the vacuum advance movement in the distributor. On my electronic engine I see no such movement.

Yah on these engines the ignition is completely controlled by the computer there's no way to advance or retard the timing at all like you used to be able to do. Since all that's been done pretty recently try taking it to a reputable shop and have them do a top end injector cleaner. It will clean the throttle body, intake manifold, cylinders, and injectors and after I had it done to mine noticed alot of difference in how the engine ran.