yes, normal, 34-36 psi


Cheers
DD

 

Another update.

The cold running problem (bucking, hesitation, "won't take any throttle") became bad enough to force me into action. Warm running has remained flawless, better than ever.

Long story short, the TPS failed. Again. This is the second TPS failure in the last 12-15 months.

The closed throttle voltage was sometimes .34-.36 volts and other times .85-.90 volts. More importantly, the voltage would drop but suddenly at about 20% throttle opening. So....I'm back with the Mustang TPS. Engine now behaves very well, cold or warm.

The problem with the Mustang TPS is that it won't go below about .50 volt closed. Even though it is technically incorrect, from the driver's seat I can't feel, see, or hear any problem resulting from this.

I've been through so many TPS removals and adjustments in the last 12-15 months I can't even remember them all at this point. I can't even remember why I decided to try the red TPS. Maybe I was just curious? I dunno. But the Mustang TPS is staying there until or unless I have the ambition to research some other substitute. I can't promise that I'll ever be visited by such ambition . It will never be another red TPS, that much I can say for sure. Incidentally (and I've probably already mentioned this), if you order a Jaguar-packaged red TPS you get the very same no-name, no-markings, brand-x part that you get if you order aftermarket. It's just that the Jaguar-packed part is 25% more expensive.

I'm reminded of my experiences, many years ago, with aftermarket replacements for the old "Bournes" TPS. Same thing. Premature failure.

Anyhow......all's well again ! This old Jag is such a joy to drive. What a car ! Worth the effort.

Cheers,
DD

 

Interesting troubleshooting. My initial thought was a plugged fuel filter, as I had a co-workers Astro van exhibit the exact same tendencies. Changed the fuel filter and it ran like new. When you said the fuel pressure was good in my head I'm saying "yes, but what about the flow?" - a mostly plugged filter can still provide pressure, but low flow.

I'm assuming that there are no more NOS TPS's to be had? The originals seemed to last a long time.

 

The originals were Lucas. I don't know when they became NLA

A person might be better off with a good used Lucas TPS than a new aftermarket

Going back to the original story, I didn't check the fuel filters simply because the full throttle power was so good I didn't they could be plugged

Cheers
DD

 

I doubt Lucas made the rotary potentiometer that is a TPS.
Bournes and a few others make those items as a regular product, Lucas probably bought them.
That type of product can use a wire wound resistive track. They are the longest lasting and more expensive.
Otherwise it is a resistive element deposited on a piece of fibreglass or similar.
I have a solid state type on the HE engine in my 1979 coupe. They were sold by Radio Spares for a reasonable price but I do not see them in their catalog any more.

There is the possibility your flaky TPS was the culprit of the engine problem you reported.
You said it gave erratic readings of voltage.
That could be interpreted by the ECU as being a rapid increase in voltage which will enrich the fuelling.
The TPS low end signal, below about 0.4V, tells the ECU the throttle is closed and the fuel cut off should be enabled above 1500RPM if the car is on the over run.
It has been said the engine will run O.K. with the TPS disconnected, you just lose the features mentioned above.

On the subject of injectors:
Four years ago I started using Lucas ( not the price of Darkness ) fuel additive, which promises multiple benefits ( snake oil ? ).
That was for my V12 5.3L coupe and convertible, and my 3.5L V8 2003 XJ350.
My interest in it was to add lubricity to the fuel and help increase the life of fuel pumps ( had a few of those fail ).
My XJ350 was the daily driver, the 2 XJSs occasional drivers. I was also hoping the additive would settle in the two V12 manifolds and cylinders after switch off until driven again.
I gave my XJ350 to my stepson last year and he thought it ran a bit rough so suggested an injector overhaul. Hence we took the injectors out after 120,000km and 19 years service. The injector specialist gave them a test and said they were perfect, needed nothing doing except I think he might have put new pintle caps on them. A new MAF made things better.
I do not have any connection with Lucas, but it seems the 1 or 2% extra cost of the fuel with additive in it might be worth the trouble.

 

this works for me!

this works for me ,$3. usd , radio shack when in business! resistor wound wire!

 

When you say "works for you",,, how does it work?

Can ya give some details?
Part number or specs of the unit/gizmo?
How it all comes together,,,?

 

i have NO idea how it works , 27yrs ago i had troubles with the factory junk, a guy said try this?
all i know is it works , seems i remember it took a couple adjustments, before it was OK!

 

JJJ
Any three wire 0 to 5v potentiometer will do the job. I think you need a 180 degree sweep, whatever the original is, and then just a bit of work to get it attached to the spindle is all. This link may help, but the sweep on the diagram is too large:
https://arduinogetstarted.com/tutori...-potentiometer

A Hall effect one is in theory less liable to wear out.