Speed Six & AJP8 TPS possible alternative

[Modrich]

So after experiencing an issue with high idle speed with a warm engine (1700-2400rpm) which could point to dodgy throttle POTs/TPS sensors I noticed that 'Mr Nice Guy' has just found a potential alternative to the OEM ford white and blue sensors.

He has succesfully fitted these to his rebuilt AJP8:

https://raceworks.com.au/sensors/throttle-position...

The sensor seems to be a Wabash 971 available as OEM fitment with connector built-in (971-0001) and with bare wires (971-0002) see below, Radward also list a few different variations of the 971:

https://www.radward.co.uk/wabash/oem-971-0001

https://www.radward.co.uk/wabash/971-0002-08680

A couple of companies sell them with what appears to be the correct connector already fitted for about £75:

https://www.webcon.co.uk/products/10391-universal-...

https://gradient-engineering.com/product/throttle-...

I've managed to source 4 971-0002 remaining stock from German ebay, should be arriving next week.

A word of caution, Mr Nice Guy had to adjust the mounting hole positions to get this sensor to the correct 0-100% reading in the ECU of his AJP8, but there is no hole adjustment on the Speed Six throttle body, there is a few degrees rotation on the 971-0002 mounting holes though. The idea of using these is hopefully they are better quality than the alternative sensors available...

I will report back my findings when i've managed to trial fit them.

[s6boy]

Excellent. Looking forward to this.

Surely it been asked before but why didn't TVR just fit one pot between the 2 banks

Edited by s6boy on Friday 18th April 08:10

[Granturadriver]

It is excellent how you always familiarise yourself with new issues and then share your findings with us here. Thank you very much! I look forward to your further reports!

[Modrich]

Thanks GT, it's important to open up topics on this sort of thing, there's always someone out there with more knowledge that can help progress a potential solution...

[Basil Brush]

I only had a quick google of the ones he'd used on the video.

Based on your info, they are listed as in stock here in the UK for £66 each as well.

https://kitspares.co.uk/products/tps-sensor-for-th...

[Modrich]

Thanks BB, it might be best for most to get the ones from webcon for £75 with the plug already fitted. I managed to get 4 from Germany without plugs for £120, unfortunately the last they had, not arrived yet. Plugs ordered separately.

[Modrich]

The good news is, the throttle pots arrived after being stuck in customs from Germany, the bad news is they'll need an adapter to make them work as a replacement for the blue throttle pots, the other good news is that the offset adapter plate is quite easy to make and I've made and have it fitted and set-up correctly...

Correct plug fitted to the Wabash 971/0002 TPS. The TPS feels very solid and has some weight to it compared to the cheaper copy blue TPS I removed so hopefully it is more reliable/better quality...


Offset adapter plate and TPS fitted






Throttle % matches cylinders 4, 5, 6


As it turns out, it was a waste of time ordering the TPS from Germany as they can be purchased for the same price from Radward.co.uk but you'll need to fit a plug. Otherwise order from the links above with plugs fitted.

The good thing about this TPS is it should be compatible with the white TPS on the opposite end of the throttle bodies without an adapter plate. I will test it when I get around to removing my throttle bodies to have the bushes/bearings fitted and do a general refurb.

Edited by Modrich on Sunday 4th May 21:10

[Modrich]

Well, it looks like I've cracked it.

I’ve worked out how to use these Wabash 971/0002 TPS sensor without adapter plates, but a little fettling is required.

So initially I thought I would need an adapter plate for the front (blue) TPS as below...


...but hoped when I got around to doing the rear (white) sensor it would be a straight swap, but when trying it after completing the throttle body re-build the TPS worked in reverse in place of the white TPS, so when the Wabash TPS was plugged in and fitted to the throttle body with the flap closed MBETool reported fully open 95%, flipping the TPS fixed this but an adapter plate would be needed and it was working against the spring of the TPS when opening the flap, not good.

Then I checked the wiring to the rear TPS and the earth and 12v feed are swapped to suit the white TPS. Swapping these wires on the Wabash TPS plug fixed.


But an adapter plate was still needed as with the blue TPS. Then I thought about swapping over the butterfly spindles from the rear throttle body to the front and vice versa and bingo! The spindle angles are designed to work opposite to each other so swapping them brought them inline with the Wabash TPS which now fit without any adapter plates and work perfectly.

So, swapping the earth and 12v feed wires on the Wabash TPS connector for the rear white TPS


...and swapping the spindles means these TPS are now universal fit in place of the old poor quality white and blue sensors.



Once the TPS are fitted to the throttle bodies as above with the flaps fully closed and plugged into the engine loom, select 'reset throttle' in MBETool and the throttle % will show 9.5% for both banks which is fully closed.

[Cristio Nasser]

My idle inexplicably goes high when then engine is properly hot. Eg after sitting in traffic for a while. Still does it even after a full throttle body rebuild with bushes and insulated throttle body gaskets, which was disappointing as I’d been led to believe worn throttle bodies was the cause.

Anyway, are dodgy throttle pots actually the cause of this high hot idle symptom? I was thinking about buying those posh replacements from Motaclan, with plenty of folk saying they work well. Just a bit reluctant to drop 500 quid on a “maybe”. Especially if this option works well.

https://motaclan.com/product/pot-throttle-upgrade-...

[mk1fan]

Nice work Modrich.

Don't see a problem with swapping the connector to an ampseal or similar.

[Modrich]

Cristio Nasser said:

My idle inexplicably goes high when then engine is properly hot. Eg after sitting in traffic for a while. Still does it even after a full throttle body rebuild with bushes and insulated throttle body gaskets, which was disappointing as I d been led to believe worn throttle bodies was the cause.

Anyway, are dodgy throttle pots actually the cause of this high hot idle symptom? I was thinking about buying those posh replacements from Motaclan, with plenty of folk saying they work well. Just a bit reluctant to drop 500 quid on a maybe . Especially if this option works well.

There were 2 reasons I refurbed the TBs and replaced the TP sensors:

1) It failed on emissions, lambda was very high which pointed to an air leak, but I've since re-fitted the exhausts after finding the slip joints weren't sealing well so this was most likely the cause. The spindles on the TBs were all actually very snug so I've just added sealing washers to be sure no unmetered air is getting in.

2) High idle speed when hot like yours (around 4500rpm!), so hoping when I've rebuilt it all with these new TP sensors it will be cured, I will let you know, these TP sensors are a fraction of the price of the Motaclan upgrades, hopefully they work as well as they do. I've also made my own PTFE 2mm TB gaskets to help with heat transfer and air leaks.

Edited by Modrich on Tuesday 16th September 08:57

[Modrich]

mk1fan said:

Nice work Modrich.

Don't see a problem with swapping the connector to an ampseal or similar.

Thanks MK1 fan

Yeah there are better connectors that could be used, maybe after I'm happy everythings works as it should