Hi all,

Hope someone can help with this as I am out of ideas!

My car is a 1998 XK8 - When I take my foot off the throttle the car will stick at around 1500 rpm for a few seconds before dropping to normal, this makes downshifting a little jerky so say the least!

So far I have cleaned the throttle body, replaced the throttle body with another used one, replaced the inlet manifold and throttle body elbow gaskets, cleaned MAF, checked all vacuum pipes for air leaks, cleaned the injectors with an ultrasonic cleaner, checked fuel rail pressure (around 40psi) and reset the ecu with battery disconnected several times!

Also noted that the car has negative long term fuel trims (around -10) if this may be related?

Can anyone give me any guidance on what to try next?

Thanks in advance!!

 

Throttle position sensor would be my guess. They have a tendency to wear and cause this type of problem.

 

 

This is a total guess but ....................... do you have cruise control, and is it working properly ??
I think your car would have the early vacuum operated cc, so an issue with the vacuum pipes or solenoids **might** have this sort of effect .......... possibly ??

 

Good guess... but no cruise

 

As I was reading, I was sure you were going to say positive trims

You mean the trims as it does it?

What are they like at idle?

 

Hi, the trims are pretty much negative all the time even on idle.

 

Any time the throttle is disturbed, the battery has to be disconnected to reset the base throttle adaption. Has the battery been disconnected??

 

Yes, I have disconnected the battery a few times.

 

I always like to start with the easiest (no cost) solutions first. If the throttle is sticking:
1. Try spray lubing the cable.
3. Check for slop in the cable.
3. Check the tension on the return spring.
4. Check around the accelerator peddle in the foot well and see if something is rubbing the pedal.

Just a few random thoughts ignoring electronics.