So this weekend I decided to change my filter to a K&N, clean the Mass AirFlow Sensor, and clean my Throttle Body. 1996 XJ6

Took everything apart, cleaned it up well, and put it all back together. Took it out and ran it some 0-60's, and put it through its paces. Everything seemed real nice, and responsive. I also added some BG44k additive to the gas, could this have clogged catalytic convertor?

Next day head out for Sunday drive and car has super high rev hang. Wants to stay in lower gears and wont upshift, almost redlining at 70mph. Then total power loss, surge back but can only drive home about 40-50 MPH to keep RPMs low enough.

What could be causing my shifting issues? Must be related to the work I did, so I am thinking problem with Air Flow Sensor or maybe Throttle position sensor? Any suggestions?!?!?!

Total disappointment in that I did all this work to help the car and maybe I did something to hurt it?!?!?

 

Well, you have named the most likely culprits. the engine conditions are used by the transmission to select gear changes, so if any of the important engine stuff is wrong, it will misshift. Any codes yet? I would certainly check the connectors to make sur they are tight.

 

I have a 1995 with 89K on it. Just completed a 3k mi vacation trip in it last week and decided it was time for some maint. I cleaned/re-oiled the K&N with near 25k on it since installation, changed fuel filter, changed oil and filter and cleaned the TB. However, I did not mess with the TPS on the bottom of the throttle body. The li'l brass torx screws are notorious for stripping out. I put a tool to them and applied some torque, but gave up short of anything starting to turn or yield.

Mine was running great before I took it apart. After, it started and ran fine, but when I would run it up off idle (static, in P in garage) it wanted to hang at whatever rpm I went to....would sit there, or maybe start a very slow decay, until I "punched" it when it would go back to idle....and....would then fall below the normal 700, to 500 or 600 and "hunt" and stumble, even stalling once. Restart was rough and unsuccessful and I was thinking, "I shouldn't oughta done this..." but I hit the return spring and it's shaft with a few squirts of silicone lube spray, restarted and it is running great since. Hope you get it sorted....I haven't experienced any issues with shifting at all....put 100 or so miles on it since the maint.

Good point SParkenzap....make sure all connectors and vacuum lines are properly secured....

 

Update,

Took everything back apart, made sure everything looks good, put it back together and same issue. The car starts and idles fine. Get on the road and seemingly shifts through 1st and 2nd no problems, but the minute you get on it RPMS go up and stay there. Let off the gas and RPMS stay high and drop very slowly, just does not seem to upshift. Still no error codes and I dont think it is the tranny. Something is causing it to not upshift properly.

Any help is appreciated. Would Throttle position sensor alone cause this? like I said it starts and idles fine. Goes fine down the road until higher speeds. 50, 60, 70mph the RPMs are just screeming. What the hell?

 

What happens if you use the U gate and shift manual does it upshift them? Just a thought.

 

Ok I checked the TPS and it seems ok.

There are 3 wires, black (left), green (middle), and blue (right). Here is what I did.

1) Hooked Voltmeter to black and green, reading was 0.5 at idle and went up close to 5 volts at full throttle as I manually turned the throttle.

2) Hooked voltmeter to green and blue. Measured 4.85 at idle and down to .5 at full throttle.

Now I am really stumped as the TPS seems to be working....

I have not tried manually shifting by using the U as I figure something is definately wrong here, and if it doesnt work like it should I dont really want to drive it until this is figured out.

 

Hi there, I seem to be in the same situation with the shifting problem, only between 3 en 4th gear though , did you have any luck on solving the problem, my best guess would still be the TPS ? Did you ever think of the ECU or TCM ? Please let me know how your doing, would help me a lot, gr

 

Hello, I finally had to break down and take it to a jaguar dealer. They ran diagnostics on it and found a shorted wire that in turn shorted out the kick down switch. That kick down switched was causing my severe shifting problems and it would just redline and rev leaving it undriveable. Total cost me around $450 for the hour diagnostics, finding the wire and replacing the switch. Hope that helps.

 

Thanks for the update!