Hi everyone,

I remember reading on somewhere online that the TPS could be replaced from underneath (on a XJR6), without having to remove the complete throttle body.

However, when I had a look today, i could barely access it, even after removing the oil filter. I feel like there is not enough space to remove the screws...

Did anyone replace the TPS without removing TB? Do you have any advice? I guess removing the oil filter support could help?

Thanks for your inputs!

 

The TPS adjustment is critical so I personally would not remove it until I had a understanding of it

There is a simple meter test you can do before removal or adjustment

I was able to remove it or adjust it from the top side with the TB installed but that is a normally asperated engine

 

The XJR6 throttle body is a b****r as I suspect you have just discovered! Having removed mine multiple times, from above and below, from below is by far the easiest if you can get under the car comfortably, ideally on a lift. I have been able to change the IACV without completely disconnecting the throttle body, but I did have to unbolt it. I was able to leave the coolant hoses attached, which avoided two PITA tasks. That said, I had removed the IACV shortly beforehand, so knew the attaching screws would come out, which they often dont.
The TPS would be much more awkward to do without completely removing the throttle body from the car, and the coolant hoses are awkward and tedious rather than difficult to remove, so I would be inclined to whip the whole thing off, enabling you to clean it, and fit your new TPS carefully and correctly.

Opinions differ on whether the new TPS needs calibrated: my experience suggests it doesnt. Disconnect the battery before you start working, and reconnect it after you finish, and the ECU will adapt.

I think there is a step by step guide somewhere, but in short, you need to take the oil filter off, remove the flexible piping from the intercooler to the throttle body, and remove the bracing bracket from the engine block to the intercooler. From above, remove the metal elbow and flexible pipe from the supercharger to the intercooler Fairly easy to do, and you will then be able to see the rest, which is fairly obvious.

 

From the ECU connector you can test it with a meter on pin Red 11 and Red 12

You would be looking at resistance and it should never suddenly spike high but a smooth change as you very very slowly press the accelerator pedal

There is a target voltage value of 0.60 + or -0.02 volts DC at the throttle butterfly idle stop as you have the ECU connectors on and you can read this by nicking the insulation off the Green / Yellow wire as it goes over the fuel rail and enters the cabin at the rear fire wall , you would not need to run the engine but have the key in the run position powering the ECU and TPS sensor



This is a different way of looking at it as you have the ECU connector off and you are not powering the TPS

 

I never saw it on an XJR6 but I assume its very similar to standard NA car from underneath and if you remove filter and housing you should have plenty of space to undo the TPS, its only attached with two smallish screws. You can test it with an OBD scanner and key in position 2(not started). TPS should be linear and go between ~0.57V and 5V with the foot down(or if its in % its between 11.37% and 100%). You can also record it while driving in case there are voltage spikes from it.
The bottom value is crucial here and its stored in the ECU as TPS idle voltage so before touching it you need to record it and when replacing it you need to make sure that new sensor also shows exactly the same voltage with the foot of the pedal. If you dont and it shows more than a 0.02V difference compared to old sensor you'll get high idle or if its somehow lower, you'll stall engine. If you dont know your base TPS voltage(or base voltage is completely out of spec) then after replacing it you'll need TPS adaptation or again, undo the screws but not remove them, start the car and turn the TPS with hand to one side until idle settles, then tighten screws.
It might look like there is no adjustment in the screws but there is plenty to change the voltage probably up to 0.1V which is enough to cause a 2200RPM idle if you're unlucky.

 

I'd remove the throttle body and take out the TPS on the bench. The reason is the screws are Loctitied in place, and unless you put a torch on the screws to break the bond of the threadlocker, you're going to shear off the screws. Ask me how I know.

You need to heat them to around 250F/130C to break the bond.

 

I’ve not had trouble removing the TPS screws/bolts. The IACV will almost certainly snap because of the loctite used.

 

You're right, I was forgetting which was which.