there’s a shop in sydney that has the tool to reset tp base idle. takes literally 1 minute and problem solved for a while until you can get a new tps

 

I'm not familiar with the IAC reset but beside that , probably needs some miles and cycles for the ECU to find itself before spending money on a shop

And a good Italian tune up as you have been idling around in the driveway with an out of tune regulation ( rich mixture )

 

You can plug it in with the engine now running. It'll work great until you restart the car. That's just to tell you that the IACV can work properly and that there is probably something else wrong. Who knows?

 

The more i think about it, the more a bad tps makes sense.
so adjustment might be needed.
if my torque reading is accurate and it is reading 10.59 at idle when it should be reading 12.5 that means the car thinks the throttle is too low and compensates by opening the IACV to increase the airflow.
But if the throttle is physically at the right spot this results in increased airflow and therefore high idle

 

12.9% is the lowest it goes for the XJS. The x300 may be different. You may want to read through the forums, or look in a service manual. I don't want to lead you down the wrong path.

The TPS can be adjusted manually. You'd have to remove the throttle body, probably widen the screw holes on the TPS, reattach with the screws just firm enough that you can rotate the TPS with a little hand force. Then with the car on, and the engine running, rotate the TPS until idle RPMs is where its supposed to be at and lock down the screws. You'll be doing this in the blind, since the TPS will be upside down in a somewhat restricted area.

 

I wouldn't touch the TPS adjustment just yet and lose what you have., There is based one resent example where the idle TPS reading is learned by the ECU and is fine if off from the paper factory value ( 0.60 + or - 0.02 volts DC )

You can see if there is a bad spot on the TPS which would put the ECU in and out of optimal mode operation which can drive troubleshooting logic nuts

 

Well i have to wait until i fix my front crank seal before i can do anything else….
and then i guess i will take it to a specialist and have them test/check/recalibrate the tps and see if that works. Troubleshooting is annoying.

 

All they will do is plug it into a machine and press the "Reset TPS" button and POOF! it will be reset!

When you get the car back, I would get a multimeter and record the voltage at idle from the TPS so you know what value the ECU will now use as a baseline. It might become helpful if you have throttle issues in the future.

 

**edit was not getting proper reading**

 

ok. so i tested again and got proper reading,
it seems that it is reading too low of voltage.
throttle closed it is reading .53v
it then moves and climbs nicely reaching full 5.01v at WOT.
so for the most part it is noce. but it is reading the throttle as more closed than it should be and obviously opening the iacv too much

 

it all depends on where the closed base idle was learned. these ecms have trouble learning the correct idle voltage sensor output drops down from the original adaptation position, up doesn’t seem to be an issue.

when you relearn the adapt position no more problems. i think old jaguar australia/cambo is near you

 

trouble is just getting it anywhere anytime soon.
I have rang one Tony Arditto who is a jag specialist not too far from me, i am hoping that he can get my car in next week to do the front crank seal, but he is really busy and may not be able to.
not sure if he has the tool or not, will find out when the car is there.
and then I rang Dr Jag who from what I have heard is one of the best around and speaking to him he seems to really know his stuff, but he has a 2 month waiting list. so i will book the old girl in for a check with him but it is going to be a while.

had not known about Old Jaguar, will check em out.

 

yup he’s on the forum as Cambo

 

just checked his website. seems great.
saw he has listed as a project working on reveres engineering for AJ16 engine tunes.

by the looks of some of the work he does, he will probably be a fan of my LED headlight upgrade and Android Head unit install.

 

Tried to do that reset thingy on the iacv and got no change.
maybe the iacv is cooked.

anyone had any luck with chinese parts?
loreada look a proper company. So thats a good sign
Loreada

worth a try?

Jlm1285

it is LOREADA LRD-153

same as this
Lrd-153

 

If you followed the procedure and nothing changes, yes, I would believe the IACV to be a problem.

Once you successfully get those 5.5mm bolts off the IACV, swapping it out takes minutes. I'd try aftermarket without hesitation here.

 

already had mine off to clean it in an attempt to get it working.
i decided to order one of the above, got it for $40 AU incl shipping... just gotta wait for it to come from china now.

 

I am planning a 2nd year clean of the Throttle body and intake components.
I just ordered a $12 dollar IACV on the Bay, seller is eccppautoparts. The pintle looks correct and it comes with a years warranty (for whatever that's worth).
What could go wrong?

 

I’ve used the cheapies from eBay.

years later, no problems.

 

That's good to know. I'm hoping the one I get comes from a good batch, will clean the existing IACV and keep it in the car just in case.
The problem I'm trying to solve is occasional blips to an otherwise very smooth idle.