My 1999 XK8 idles fine when cold (750 RPM), when it warms up it will drop to 550 - 600 RPM. The low idle seems to allow the transmission to slip out of gear and when I start to accelerate from a stop it appears to jump into drive. Transmission had a total rebuild with no change. I can adjust the throttle cable to get the idle up to 750 RPMs and the problem goes away.....adjusting the throttle cable is not the fix because it raises the cold idle.
Did a smoke test and found leaks in fuel injector, replaced the injector seals and no vacuum issues.
Throttle Positioning Sensor may be an issue, but I haven’t touched it.
Any suggestions as to my next step?

 

Welcome to the forums galearmstrong,

I've moved your question from General Tech Help to XK8/XKR forum. Members here with the same model will be able to help.

Graham

 

On the right side of the throttle body is a sensor you can adjust. May be a zero dollar repair if you're lucky.

Check out this Youtube video for a simple re-alignment of the sensor. The bit you're interested in is about 9min into it.

 

Welcome galearmstrong.
What does the car think is wrong?

Have the ODB codes read or, better still, get a cheap ELM327 clone to work with your phone. It will be a useful addition to your toolkit in any event.

Post back what you find:- the raw codes, not any interpretation of them.

Good luck.

 

I do have an OBDII reader and I don’t have any codes. A few months back I was getting left and right bank running lean (codes may have been 107 & 109). Did a smoke test and had bad injector seals, replaced seals and haven’t had any codes since. Thought replacing the injector seals would increase the vacuum and therefore increasing RPMs. Cold idle seems good at 750, but warm idle is a bit low.

 

Which do you have (pending) P1000 or P1111?

What are the fuel trims (hot engine) at idle and again at 2500rpm?

 

No codes now, but was p1000
Not sure my reader handles fuel trims!

 

P1000 is a code that says that allllll (theres really just a few) of the systems that need to complete a cycle to show "readiness" have not yet completed and they are in process to give the "ready" or p1111 code...

Over a looooong period of time the car probably got very used to a situation where there was extra air and most likely fuel being added due to the leaks you had (and the auto adjust at the butterfly disc in the TB closed way down - maybe completely),,, so the ECU is lagging behind in dealing with the changes you made. What I think I learned is that with this adaptive system, which is slow to adapt in both ways, doesn't like sudden changes (like air and fuel ratios) and can't alter itself very quickly when a change like yours is made. Blah blah blah,,, sorry.

What I would do is take a large pair of vise grips and lightly clip the negative battery cable (removed from it's terminal) to the positive battery cable and terminal and let the capacitors in the ECU (and other systems) drain aka a hard reset.

Then, start the car from DEAD cold. Let it slowly come up to full operating temp and turn off the car. Then immediately (and maybe someone will correct me at this point - or any) restart and take a nice easy drive. Should give the ECU a chance to correct to the new normal that you've created thanks to your amazing work with the seals! Good catch BTW...

Might help...?

 

My low idle just got put on the back burner.
The rear main seal blew out....has anyone experiences this issue? While driving my 1999 XK8 left a trail of oil. Pulled the cap on the bottom of bell housing and could view the seal. At repair shop to replace the seal, but this seemed strange to me as to why it would completely blow out. Is it a pressure issue in the crank case? Don’t want to replace the seal and not identify the root cause!