Ford V6 TPS spins in the opposite direction

 

First off, it was indeed a Ford stamped part. I also ordered an OEM replacement a number of years ago, but I don't recall whether or not the replacement part also carried a Ford stamp, I don't believe it did. I have searched forums, but no one has posted any success with a substitute part. It's too bad, that TPS is several hundred dollars! (similar situation for ABS Wheel Sensors, except that they do not have a Ford stamp)

Second, you were smart to order the OEM part. I have read about the horrors of throttle body access for the supercharged 4.0.

Lastly, if you wear away the metal track, shouldn't the voltage go down, not up? High idle is a result of a higher voltage reading. I can't think of a situation where the degradation of this part would lead to a higher voltage signal.

I've enjoyed this discussion, I am always interested in learning from others. I respect your knowledge of these parts....

 

Vee,
I very much enjoy these discussions too, and find that I learn a lot from them; sometimes too late as I have already learned the hard way!
I guess our discussion so far has amplified a couple of points which might be of help to others should (when!) they encounter the high idle issue. Firstly, stick with OEM until someone definitively validates an alternative. Secondly, Adaptation may not be necessary after a new TPS is fitted. Suck it and see
The OEM part doesnt carry any Ford branding or markings to connect it to them, hence the ongoing uncertainty, but I would bet that there is interchangeability with a Ford model of some sort. Maybe somebody with a normally aspirated car could try one out? It is just too difficult to access the supercharged throttle body to take the risk.
Exactly how a failing TPS misreads is a good question, and like you, my initial inclination would be that degredation would reduce rather than increase voltage. If the degradation was due to the ingress of a contaminant, it could cause a shorting of the rheostat I guess, but another possibility is that the TPS actually reads from high to low, ie the highest voltage is at idle, and reduces as the throttle is opened. I have seen reference to the range of expected voltages, but when I checked mine, I used my scanner, which reported the output as a percentage rather than an actual voltage. I have come across TPS which work from high to low, but do not know whether the X300 works this way. Someone here will know! Another possibility could be that the ECU defaults to some mapped settings in the absence of a reliable signal. I can understand why this wouldnt be such a great idea at speed, but an extra couple of hundred Rpm at idle at zero speed wouldnt be a big deat to keep the show on the road... Again, just a guess, someone here will know.
Talking about this is so much easier once the problem has been solved. Therapeutic almost!

 

I have attached some info on the Jaguar TPS which may assist.
I have spent considerable time on the internet attempting to match up an alternative, all to no avail so far.
Main problem seems to be rotation direction. Despite finding many similar Ford parts which appear to match in size, hole centers, tang position etc. majority run anti clockwise direction.
The Ford number 70418A on the original is of little use, it is unique to the Jaguar OEM number JLM12074. As many may have discovered, entering the Ford number just brings up the OEM TPS.
Its a challenge !

John Herbert
1996 XJR

 

I apologise in advance to those who know more about electronics than me, of whom there are many. When I was working myself up to shell out for the OEM TPS replacement, I did wonder about an alternative solution, involving fitting a cheap replacement TPS which physically fitted, and wiring another variable resistor between it and the ECU, the idea being to use the variable resistor to "dial in " the correct voltage which the ECU was expecting. As is evident, I didnt pursue this line of thinking, but continue to wonder whether it has any validity.

 

I will probably start my own thread for this, but a long time ago I used to have an issue where the LTFT would be somewhere consistently sit at 10%.

I threw all sorts of parts at it until one day I finally gave in and spent the money on a new OEM TPS. It was a lot of money for a part that had tested perfectly well. After a few days of driving, the LTFT began to drop. After about a week, it was at zero. The new TPS had cured some mystery issue. I was happy.

Fast forward to this past spring, maybe summer. I noticed that the LTFT had crept back up and sat at 7%. I had noticed in the past that at times my crunchy TPS harness would need adjustment to get a high idle back to normal. I bought the right connectors for the TPS, EGR and even replacement gold plated weather tight female sockets for the ECU! I also bought some 16 gauge GXL wire in the proper colors (with stripes) and removed the female pins on my ECU, removed the 2 pins from the EGR and I reran fresh wire, from ECU to TPS (and to the EGR where applicable), with a fresh TPS three pin female connector. My LTFT is back to zero! It didn't take long for that change to happen at all, perhaps 5-10 miles.

Not sure if this has any relevance to anything in this thread, but I thought I would share.

 

Vee,
That is very interesting, and might play to the theory that added resistance pushes the idle up. In the same way as you cleaning the connectors reduces resistance and the idle speed, so a new, clean, TPS does the same. Given the age of these vehicles now, cleaning the connectors might be a better place to start when chasing a high idle. It is certainly cheaper, and in the case of the supercharged cars, much easier than the TPS.

 

Great thread, guys!!! I just rated it 5 stars!!!

Regarding the keep-alive memories, my recollection is that they are powered not by batteries but by capacitors, and when a "hard reset" is performed by connecting the battery negative and positive cables, the charge stored in these capacitors is drained off, clearing the memories. The capacitors for some memories are isolated so they cannot be drained by a hard reset.

Cheers,

Don