4.0 Acceleration/Speedometer issue.

OK here goes, I have a '96 XJ 4.0L. For the most part it drives great. If you let it accelerate normally, you can't notice there is anything wrong except for the erratic speedometer, but if you accelerate hard enough for the tranny to downshift, it will fall on it's face, which, at that point I remove my foot from the gas and then the car will be fine as long as I return to normal acceleration. The engine has 110,xxx miles on it with a new catalytic converter and 2 new O2 sensors. The problem began as an intermittent issue, but now seems to be all of the time. Also, the acceleration hesitation goes hand in hand with the erratic speedometer....ie...if the speedometer works correctly, I am also able to hard accelerate, but if it's erratice then I can't. There are no check engine lights whatsoever. Any help would be greatly appreciated...

"IF" the speedometer works correctly? Vehicle Speed Sensor is faulty or has a bad connection. Needs to be replaced. Been there, done that, realized I was doing Mach 2 in a school zone.

I had the erratic speedo on my '93 XJ 2WD Auto that was driving me bonkers.
See previous post (no responders).

The pointer would flicker and drop to zero occasionally. I changed the sender
and made extra-sure that the gear adaptor was oriented correctly. I pulled
the instrument cluster and checked the connector there. No improvement.

I also had a hard start problem. The O2 sensor is new; fuel pressure OK;
good spark; I changed the CPS; carefully cleaned the idle air motor pintel;
threw in a can of Chevron fuel cleaner. Again, no improvement.

Last weekend, in a bout of primate-like frustration, I went through the entire
engine bay disconnecting, inspecting, and cleaning every single electrical
connector I could lay my mitts on - using a can of Dust-Off, a dry toothbrush,
Q-tip(s) & dielectric grease.

When I finally got off the big ECM connector (next to the aircleaner) - it
looked as though somebody had tossed a small handful of dirt & sand in there.
It also looked like it had gotten wet, then dried, several times over the years.

Ever since cleaning the ECM connector:

1 - the speedo has been A-OK.

2 - the hard start problem has been improved...but not totally "cured".
It still takes me two, short, spins of the starter to get the engine
to fire up. It's not "perfect" - but it's much better than before, as
I would previously have to spin the starter for a l-l-l-o-o-o-o-ong
time before the engine would roar to life.

Don't forget to disconnect the battery before doing any of this!