I have a 1996 XJS with the AJ16.

My car has recently developed a sticking gas pedal. It takes extra effort to initiate the gas pedal once your foot is off. Once you get past the initial "bump" it actuates just fine.

I popped open the hood to actuate the throttle by hand. Sure enough the throttle body is the problem.

I played around with the assembly, initially thinking it might have to do with the cruise control linkage. What I found was that when I pressed down at the spot in the photo, it worked fine. Nothing else I did to the throttle assembly made any difference. Only adding pressure down on the point identified on the photo.

Other than a recommendation to get in there and clean out the throttle body, is there any other possible cause/solution to this issue based on what I've mentioned above?

Thanks.

 

Hopefully someone with a 6 cylinder can chime in but without having it in my hands and with no experience I can't give you anything specific. If pressing on the throttle assembly/linkage frees it up, then obviously your problem is there. It is binding for some reason. Something must be loose from either being worn or just not being in place or adjusted properly.
You need to determine what is allowing this movement and eliminate it. Look at the assembly and see what part is actually moving when you press down on it. Clean your TB any way

 

From what I recall the throttle butterfly can get gummed up and start to stick; that also means that it won't close fully - is your tick over speed higher than usual?

 

I don't think so. The rest of the throttle response seems to be operating normally. I just need to exert more pressure than normal when pressing the gas from a rest position. (whether its from stop, or after letting off the gas pedal for any reason)

 

The same thing was happening to me and it was the throttle body was dirty. Pull it off and clean it with TB Cleaner. This is a known problem with the AJ16.

 

I have an 90 XJS V12. My throttle pedal is sticky in the morning at first crank up. Once I press it it unsticks and is fine the rest of the day.

tony

 

Agreed on the cleaning just on gen'l principles.

'Worn' sounds like a distinct possibilty to me.

Over the years I've worked on some old carburetors where the shaft and/or shaft holes were worn, allowing the shaft to ****-over a bit and bind up. I don't see why the same thing couldn't happen with a F.I. throttle body.

I'd be tempted to take the throttle body off the engine for a good cleaning and inspection.

Cheers
DD

 

I thought it was odd that by placing pressure on that throttle part that the stickiness went away.

That being said, as soon as I get a warm day outside, I'll go in and get that throttle body out for a thorough cleaning.

I'll post back with results.

 

Did you disconnect the throttle cable at the throttle body and then press the pedal to see if it was still sticking? The sticking has to be either cable related or throttle body. Separate them and see for sure.
Cheers, RagJag

 

Pulled off the throttle body. Holy mother of God was it gunked up. It looked ok when I pulled off the air tube. When I took off the actual throttle body, the inside part of the butterfly was caked in thick oil.

Took me about 10 minutes to give it a thorough cleaning and the stickiness is gone!

Thanks to all here who took the time to chime in. It really is not a hard job to do at all.

 

Result!

 

Oh, I apologize, I realize I never mentioned the result.

Although, oddly enough I still felt some resistance when actuating the throttle at the body itself (once everything was out back together), the result was a TOTAL SUCCESS.

It would be pointless to clean the body out while still in place. The gunk on the engine side of the throttle body was gunked up beyond belief. To get to that side of the body, you have to pull that thing off.

Now the gas pedal is as smooth as ever. No stickiness at all!

Once again, thanks to all participants!

 

Seemed strange to see the big Ford logo on the throttle potentiometer!

I cant believe that is a $100 part!!!

 

No my friend, that is a 300 dollar part !

No OBD has found, last time I checked, the equivalent Ford part number, and people on the X300 forum have been trying

 

<gulp!>

Holy moly! I inherited one of these parts when I purchased a small bin of used XJS parts for a song. It does appear used, but not abused. Is there any way to test this part?

I have to admit, ever since the the TB got a thorough cleaning, the engine has been smooth as glass. I was getting the occasional random gurgle before. It's all gone...

 

Although others might differ I will say that there is no way to test these 100%, if it's suspect, changing it out is the best thing to do.

A few years back mine was tested SEVERAL times and came up good. Car kept on sporadically dying at high speeds (like freeway speeds). I changed the "good" TPS on a hunch and car never died again.

They go bad because folks don't do what you just did and remove the whole TB. What eventually happens is all that oil and crap makes its way down to the TPS and it dies.

 

Sure you can test it, it is just a potentiometer. Using a voltmeter with the ignition on but engine not running, back probe the wiper wire at the connector. At idle you should see about 0.6v. Then slowly rotate the throttle quadrant and observe that the voltage increases steadily and smoothly with no flat spots. At WOT you should have a reading of around 4.8v if I remember correctly.

The wipers do wear over time and yes there could be ingress by oil or cleaning agents that could create a short but this test be an effective way verify the functionality of the TPS

 

That's really helpful.
What exactly is back probing? (think I might have seen in Amsterdam once).
Wot is WOT?

 

LOL, no me old china, it's got nothing to do with your mis-spent youth or public schoolboy pranks Back probing is a means to test a circuit at a connector. You just need to insert a back probe or needle or even a paper clip along the wire insulation at the back of the connector until it makes contact with the conductor. Here's a pic I nicked off the web.


WOT = Wide Open Throttle = put yer foot down!!

 

All is now clear!