hey guys ive only had my 99xjr for a month, and i think i have a problem with it. The car has 101,000 miles and whenever i go over a pothole at low speeds the car seems to choke. If im doing 30mph the rpm will just drop to 500 and the car feels like it might stall for a second. Im not quite sure how hitting a pothole would cause the rpm to drop that much. Also the car vibrates on the highway from 50 to 60 but i read that a lot of people have that, and it also vibrates a lil when it idles. Any thought regarding the above will help.

Thanks

 

I just spoke with the last owner, and he told me that the car did the same thing when he had it. He took it to his friend who is a jaguar tech. and the car had no fault codes. Any idea as to why it would be choking when hitting a pothole? Could it be the transmission?

 

Grasping at straws here - but, the throttle position sensor has gold pins and the mating connector has tin plated pins - this can cause galvanic corrosion and is covered by a Jag TSB.

Now the straws part - IF (and it's a big IF) your TPS pins are starting to get corroded, when you get the sharp impulse from the pot hole a pin or pins (only 4 there) may briefly lose contact, reporting false throttle position to the ECM. A simple test/fix is to unplug the TPS connector (on the right side of the throttle body) and spray both the connectors (in the TPS and on the harness) with contact cleaner/lubricant, available at Radio Shack. Then re-insert and remove the connection several times to 'wipe' any residual corrosion off the pins.

I was having significant throttle self-modulation issues until I did this - and occasionally they appeared to be caused by an unusually hard bump. Since the cleaning, no issues whatsoever.

The real fix is to replace the tin pins in the harness connector with gold - Jag has a set to go with the TSB... but cleaning offers a simple test to see if this is the issue, and I expect the results should last quite a while. I also did the same cleaning to the throttle body motor connector - 2 pins on this one - just because it was right there, and easy to do... You may as well do it too, as the throttle motor dropping out could also cause your symptoms.

Another check for you would be the Pedal Position Sensor - I believe the connector is on the other side of the throttle body - also 4 pins. If this connection fails similarly, the ECM may get a false report that you've taken your foot off the throttle... so cleaning this one can't hurt.