I've been experiencing a recent problem when driving the car on the highway, then continues after getting off. The car would lose power then somehow stumble back. When exiting the highway, it wants to stall until I give it more gas. Previously, I found a broken "Y" hose which I replace and things ran fine for a while. (I must note here that I periodically drive this car). Today, it started again after some highway driving. I believe this issue would point to the TPS. I undid the connectors (which were very dirty inside) cleaned and WD40'ed them. When I reconnected the TPS and started the car, it idled high and seemed to be running rich (exhaust smell). Disconnected the battery for a while and reconnected. Started the car and now it stumbles and idles low, wanting to die. Still have the smell of rich exhaust. As a side note, I tried to test the current, as per the Haynes manual. I may be having a problem with my testing (not very good with electrical issues). For tests, the ignition is in the "ON" position. I get no voltage nor continuity from the TPS disconnected and tested from its connector (that figures correctly no power because it's not connected to the harness) However, no continunity? The Haynes manual describes back testing the TPS connector. Does that mean probing from the rear of the connector? If so, I am not getting a reading from that with the connector connected to the harness. No VCM codes. I am at a loss on how to proceed. Any suggestions?

 

What sent you to the TPS? Almost any of the ignition components could cause this. With no message on the VCM, I would check for vacuum leaks first. Just a thought. Wait for more advice.

 

Ken,

That was the original culprit over a month ago which I've remedied/replaced (the "Y" hose).

I had a small smoke condition from the rear of the engine bay when this initially started. It didn't smell electrical or antifreeze related. It wasn't oil or transmission fluid burning either. Maybe the Cat's were burning due to the rich fuel mixture.

As an update, I just disconnected the TPS and ran the car. It idles high, between 1200 and 1400. Giving her gas makes it want to die. The vehicle is presently cold (not started in 3 hours).

 

I would think that should throw a code.

 

I had a similar problem, my car was hard to start, idled a little rough and recently after driving it for a while it would loose all power and only run with no gas or not run at all untill it sat for 10 mins.

The culprit was the Fuel Pressure Regulator. Pulled off the vacume hose to it and fuel just squirted out of the thing. Replalced it, and now it starts right up and runs very nice. It is an easy check to pull the line of the FPR and see if it is leaking.

 

Gunnerman,

Thanks for the suggestion. I actually was able to test the current on the TPS. It's basically dead following the Haynes manual procedure. The only problem I am having is removing the small bolts for the TPS. I will not remove the throttle body because I don't want to mess with the bell crank. I've tried the suggested 7/32 ratchet with extension and universal joint and I just can't seem to seat the ratchet on the bolt. I'm going to invest in a 7/32 open faced wrench tomorrow. Just hope Sears carries it. The local auto stores do not.

 

Gunnerman,
I don't have quite the same symptoms, but on a hot day (which we have plenty of here in Tulsa this time of year) I have an infrequent problem where the car will hesitate on acceleration. It will start normally, but after I have driven a short distance, and stop for a light or stop sign, the idle will drop a couple hundred rpm and on acceleration from the stop, the car will hesitate until I pump the gas. Very strange. Any ideas?

 

Gunnerman/Robert

I see you on JL. The problem is most probably a vacuum fault. That was my initial problem. Fpr the TPS giving up the ghost....I'll take that as an age problem. Just as a side note, while I'm waiting for my new TPS to arrive, I was scouting around and found a disconnected hose near the oil filter (you have to take this out in order to access the TPS from beneath the car). I traced it back and it originates at the air switching valve. It terminates at a check valve which low and behold, has had the nipple rot away. That's right, an open faced check valve that blows emissions from the exhaust. This probably explains the rich fuel mixture I initially had, the slight smoke condition from the rear of the engine bay when the idle problem initially happened etc.

So.......check all your hoses for cracks....even this miserable hidden one for the air switching valve (look it up in one of the Jag manuals other than Haynes. The check valve removal is not in there). It will be a PIA to remove not only because of its location but the fact that it's rusted all around there. I just sprayed some Gunk deep penetrating oil and will fiddle with it during the week to try and wrench it out. A new one is on order along with the corresponding washer.

 

I have finally installed the new TPS and electrically, it's operational. While I was down in that area, I noticed that the the Check Valve associated with the air switching valve has lost it's nipple (rusted out). Now I have a hanging tube. Presently the Check valve is a real PIA to remove. Tried two types of rust penetrate. Waiting for the second one to take affect.

Any tips on how to remove this pesky check valve. I've already ordered a new one with the washer and awaiting it's arrival.

Thanks in advance.