My 92 Sovereign with an auto trans is still going in to limp mode. I at first thought it felt like a fuel problem, as I had the code 44, but I haven't gotten that in a bit. Additionally the check engine light has stopped coming on. If I disconnect the battery for a day, the car runs and will get up to speed, but seems to not go over 2000 rpm. If I have the car in park or neutral, however the engine revs freely. It will eventually go into limp mode anyway.

I've only had the car for a short while, and it was priced to move. Didn't do a deep dive on the car or ask very many questions. After the fact however, I did ask the seller about the limping, and he seemed to not know anything about it, and this problem didn't come up until a couple weeks after we got the car.

Am I looking at a transmission problem? Should I still be looking at fuel delivery?

 

This fault is often related to a dirty TPS (throttle position sensor). I haven't had this problem myself, but there are quite a few posts about it on the forum - do a search for limp home mode and TPS and you should come up with something.

Larry

 

On our '93 the most common cause of limp home mode was oil contamination of the electrical connector for the TPS. The connector is mounted on a bracket on the intake elbow just to the left of the throttle body. Try disconnecting it, flushing both halves with zero-residue electronic cleaner spray, allowing to dry, then reconnecting. If that makes no difference, it would be a good idea to remove the throttle body, drill drain holes in the plastic case of the throttle position sensor and flush it with electronic cleaner.

The Jag-Lovers forum XJ40 eBook has an excellent diagnostic procedure for LHM if the above doesn't resolve the issue.

Cheers,

Don

 

I would replace the transmission relay too. They get old and will intermittently cut out. But the TPS should get a cleaning too.

 

I've had enough good luck repairing my other car to suspect that this won't be so easy as a fouled TPS. Of course I'll clean it anyway, but I have my doubts that it will revive the car. Where else should I be focusing my attention?

 

Don't focus your attention anywhere else until you have cleaned the TPS connector, and possibly the TPS itself. Until you have ruled those out as suspects, there's no point in doing anything else. In 16+ years of owning a '93, the only other cause of LHM we ever experienced was cracked solder joints on the circuit board in the TCM, but in every other instance it was a contaminated TPS connector.

Cheers,

Don