So i decided since it would be very difficult to change the iac valve on the throttle body of my 1996 xj6, i figured i might as well change the whole throttle body. I did just that yesterday, the old TB was grimey and disgusting, so was the hole that i took it off of on the engine. I cleaned what was visible on the engine and soaked up the throttle body cleaner, then i put the new clean tb in and swapped the TPS from my old TB to the new one, now, even after a hard reset, when i start the car it shoots straight up to 2000 rpms and stays there with no signs of coming down! Any ideas? Could it be the TPS? Could it be that the TB isnt correctly adjusted? Is there an idle screw? Thanks in advance!

 

Is there a chance that air is leaking into the intake tract via a loose connection or a vacuum hose crack? One of my machines will do this when a vacuum leak is present. My experience with DFI systems is that there is an idle adjustment, sometimes, but little else.

 

i checked before i put the air intake back on for bad hoses and cracks and didnt find any, i will check again when i get home today from work. But lets say there isnt any cracks of bad hoses, what else could it be? is there a screw on the TB that could be adjusted to lower the idle? I feel like this could be the issue, maybe the previous owner of the TB had it adjusted differently, im not sure. thanks in advance!

 

You need to slot the TPS and adjust it the way BRUTAL described in a post a few months ago or use WDS,IDS,PDU etc. to perform a throttle adaptation. You can't move a TPS from one throttle to another and have the ECM see the same reading.

bob gauff

 

Hmmm interesting, ok so i don't have access to any diagnostic tools, this sounds like something I'll have to take into the dealer. Am I correct in that assumption bob?

 

What bob referenced is a way to "adjust" the TPS mechanically by slotting the mounting holes. He referred you to a previous thread in which BRUTAL ( a jaguar dealer tech) described how to set the tps to the setup in the car's ecu, rather than setting the ecu to match the TPS. I am pretty sure bob has not actually done it that way, nor have I, since we have WDS, but is should work. If you find an indie, or the dealer for that matter, the setup should be whatever the minimum shop charge is (1 hour, I expect) .

Heres betting that when you get the TPS right, the idle settles doen almost immediately.

 

hmm ok, can you point me to the thread brutal wrote? also what if i bought a totally new tps and put it on? would that resolve the issue?

 

Not likely. The problem is that the tps has to calibrated to the throttlwe plate position. Tradionmally, that is done by having slots iin the TPS mounting scews. The tps is moved in an arc to set the correct feedback (about 10%) of the the tps range to the full closed throttle position. On the X-300, the setup is done by software. The TPS position is read by the software while you tell it that the throttle is closed and an offset is stored to apply to the feedback value from then until another "orientation" is done. So, rather than doing that, you can move the tps a slight amount until an OBD scanner shows it reqading about ,6 volts or so OR about 10 to 12 %. Once the ecu believes it has terurned to idle (after the tps says it has) it will begine controlling idle speed setting again.

The link (searched on brutal x-200 and tps)
https://www.jaguarforums.com/forum/x...e-fixed-58021/

 

UPDATE-So i came home yesterday tired from work but took a crack at the car anyway. I started it up and sure enough it went straight up to 2000 rpms! so instead of touching the tps i adjust the small hex screw on the side of the TB to see if that would adjust the high idle, it worked! no more high idle, but now its back to do doing the same thing it was doing that made me change the TB! It shuts off when i slow down, with or without brakes! if i let the gas go and let the car roll till it reaches a low rate of speed the car begins to stall! If i let it shut off the check engine light will come on and the tranny goes into limp mode. I turn the car off and let it sit for an hour and both lights go away and the car runs fine again until i deccelerate. Any ideas? Could it be that the screw needs to be adjusted again? a bad or non calibrated tps? anything else?

 

Yes. That is exactly what I would expect. The idle screw you "adjusted" is not used to set the idle speed, it is sets a minimum throttle plate openning. Your idle control system is still not regulating because it does not know when you are at idle, because the TPS is maladjusted. The cost of a new TB, the cost of a NEW TPS , Or the cost of an idle control valve are each higher than the cost to have the WDS idle setup done. OR, try Brutal's method if you are like my and just cannot pay someone else to work on my car.

BTW- you have every reason to suspect what I explained above is wrong, since I am an amateur mechanic, and what I say is half full of crap. BUT, motorcarman also tried to explain it to you and what he says can be taken to the bank.

 

I'd say you have a good handle on this one, Ross. I'll back up pretty much every word. Personally, I would only use Brutal's method as a last resort; if all else fails. He really needs to find someone with a PDU or WDS so the Throttle Potentiometer Adaption app can be run properly. That has to be done almost every time the throttle butterfly or base air is disturbed.

+1 on motorcarman...... what a resource!

Cheers,

 

Ok guys thanks for the info, I'm going to the dealer ship to ask for a tps calibration