one thing I can almost guarantee after this procedure is that the TPS will not work at all. And if for some strange reason your problem was not the TPS (I think it is) now you will have two problems.

the TPS breaks down because oil drips down there due to oil breathing down and never being cleaned at oil change intervals, as the filter is changed from below and the intake is never pulled apart for proper cleaning. This should be done at least once a year, maybe once every couple of years if your XJS is a garage queen like mine. It would probably avoid a lot of gunked up throttle bodies and ruined TPS...but again, at this point these ancillary parts have served us for 25 or 26 years. They are not eternal

 

OK now I am confused. I planned on removing the throttle body and cleaning the TPS while it is still attached to the throttle body. Will this damage the TPS more?

 

Depending on how dirty your TB is there are a couple of things you can do: You can clean it upside down, making sure nothing drips down to the TPS, or you can just soak your rags and wipe instead of spraying away at the TB.

 

There is nothing cleanable on the TPS.

there is nothing to service.

if your TPS needs to be reset, it is possible to adjust it by hand, but I can’t see how that possible with a turbocharger.

You can clean the throttle body, ensuring the butterfly doesn’t get stuck, and that does indeed need to be done occasionally, but there’s nothing to service or clean on the TPS.

 

I read an old post from Spikepaga that suggested that the throttle body be removed and that the TPS, while still attached, should be soaked in solvent. Any clarifications on this?

 

I don’t recall making such a recommendation, but if I did, it must have been because I had inhaled said solvents. The advise we are giving you here is the most sound that we know of at this time. Please kindly read thru the posts in this thread.

Good Luck

 

You could also replace the coils before you mess with that TPS.

It would be easier, but not necessarily cheaper.

 

I'm following everyones' advice and starting with the simple stuff. I'll be removing the throttle body for cleaning and also cleaning all electrical connections. I'll then progress and do everything I can that won't require a trip to someone with a PDU. Thanks for all of the advice.

 

I forgot to mention that I checked the fuel trims and it appears that I do have a vacuum leak. The readings are between -1 & +21 at idle and drop to -2 & +8 at 2500 RPMs. Once everything else is done, I'll be sending my injectors for a professional refurbishment.

 

Please make sure you are looking at the LTFT, and not the STFT. The LTFT should not change as you drive. The STFT should be constantly switching. If they're not, then something is wrong.

I'm still recommending that you swap out the coils, especially if they're originals, moreso if you're looking to avoid monkeying with the TPS.

 

I will change out the coils. I do have new ones in reserve, so I'll change them all.

 

That's a 20 minute job, at best. Put them on and see if anything changes, if not swap them back out and keep them in reserve.

Let us know what happens.

 

Just a quick follow up, a new cps seems to have solved my stalling problems. My first replacement cps was defective and I had to order and install a second new one. An old mechanic friend of mine said you should always check your work as you go to make sure you haven't installed defective parts or screwed up the installation. Good advice then and good advice now.

 

Thank you for following up. It’s always good to know how problems were resolved. It will help other people in the future.