very high idle in neutral
 

my 3.2 engine sounds smooth and drives nicely, although there's little sense of engine braking.
In D (stationary) the engine is at 1200, but if I put the lever to N it rises to 1600. If I give it some throttle it often stays steady at 2200 until I blip the throttle, when it drops to a steady 1600, and sometimes then drops again to 1200 and 900 after a few seconds.
The throttle cables and butterfly are all free and clean. There is no movement in the butterfly assembly when the idle drops. No obvious vacuum leaks. Anyone recognise this pattern?
Thanks
Tom

I would clean the throttle body and then check that it appears to close all of the way. Then use an OBD scanner to look at the throttle position while you "blip the throttle".

If you don't have a scanner, get one. It is probably the single most useful tool to work on an engine.

check your EGR, there is a service bulletin on that matter, check also for qualified recall on that part and the e prom.

Have you pulled the throttle body off to give it a thorough cleaning? Both sides of the butterfly?

some progress on high idle
 

Thanks for the advice.
I've already cleaned the throttle body inside all around. Now I've removed the idle control valve - seems sticky and i can't get s response from it so I'll replace it. British Parts were cheaper than ebay.
I'm sure the reason i can't locate the egr valve is that UK models don't have one.
What obd scanner should i buy, and how do i check if recalls (R493) have been done?
cheers

next step
 

the stppper motor idle control valve is now replaced. After some crazy idling and stalling and struggling to restart i got it going again and drove around for a while. It seems to have settled down now -hopefully the ecu has relearned the stopper control.
sadly idle as bad as ever. next i need to find a suitable obd scanner -suggestions welcome.

Tom:
First, I recommend you get a Chinese "ELM 327 Bluetooth Interface Module". Google it. The Chinese clones are obscenely cheap now, and if you get one of the duds, just order another different brand!
That assumes yoiu have a laptop with Bluetooth, running some modern version of Windows. There are several scanner programs that will interface that way and give many features like trend charts and Drive Cycle monitoring. II will look up the last one I bought, but they run less than $50.00. Most of the softwares have a try version for free.
If you want to scan the other modules besides the ECU, then AutoEnginuity with Jag extensions will cost close to $500.00, but I really use the low end scanners much more than that one.

And... many (most) of us are not mind readers! Please clarify what idle problem other than the idle speed you have. I don't think you mentioned it, at least not in this thread.

I have one of the ELM 327 Bluetooth units Ross mentions, which I purchased on eBay for around $10.00. I use it with my Android phone and the Torque Pro application, which costs about $5.00. It's really an impressive and capable setup for $15.00. The last time I looked for an equivalent program for my son's iPhone I wasn't able to find one, but hopefully Torque Pro is now iPhone compatibile.

Cheers,

Don

high idle cured...
 

great - i got the torque pro and used a plug in obd as described. only one fault logged to do with emissions- reset and now gone. i noticed that when the engine is hot, the throttle butterfly spindle gets sticky at the 'idle' end of its rotation (maybe just 1degree off) so i fitted an extra spring to pull it fully closed -see picture.
https://cimg8.ibsrv.net/gimg/www.jag...3f38205448.jpg

throttle return spring booster cured high idle


d

idle issue swapped for sticky pedal
 

...now though it takes quite an effort to overcome throttle pedal sticktion once it's warmed up. so the problem is that the butterfly shaft is sticky in its bearings. believe me I've cleaned and lubed it till the cows come home.
so i need to replace the throttle body. The ones I've looked at on ebay often have different last 2 letters on the part code ( mine is nbc3061bb) but many are given without a code, just engine size and year. Can i ignore the last letters if date and looks are good?
also should i swap my TPS over,check the butterfly opening, set the idle and do some kind of reset?

Heed this! If you do not have a way to do the TPS calibration with WDS or IDS, then read the TPS wiper voltage before dissassembly of your old Throttle body. Then, you can either assure your new TB has the correct idle voltage or you can slot the TPS mounting holes to tweek it to the right idle voltage.

sticky throttle body
 

ok let's hope my multimeter is accurate enough.
I'm now assuming the sickly throttle is either
a) the spindle bearing
b) the tps or
c) the butterfly jamming in the bore
i guess c is the most likely. i will remove the butterfly then the tps to see.

sticky throttle body
 

Thanks for that -will do.
let's hope my multimeter is accurate enough.
I'm now assuming the sickly throttle is either
a) the spindle bearing
b) the tps or
c) the butterfly jamming in the bore.
Cold it was a little sticky but ok - hot it gets hard to turn the butterfly.
I have now completely dismantled the throttle body and cleaned everything especially the spindle bore. Off the car it all moves beautifully. Test drive up to hot coming up!
Tom

idle and sticky throttle seem fixed
 

test drove up to temperature 4 miles everything seems good -what a great drive and a big thank you for the help.
i took resistance readings off the tps in case i need to swap it. easier on the kitchen table!

I doubt you need a throttle body; Take that mondo-spring off and do this:
https://www.jaguarforums.com/forum/x...carman-111454/

sorted
 

thamks yes i fitted a jubilee clip to the tb post so the spring is under more tension but this solution looks better if the spring temper will take it.
As it's running perfect now ill gi to find the correct part.
My problem was ultimately the butterfly jammimg in the throttle when closed and hot!
cheers
tom

I found the part quite cheap ($3-$5) and plenitiful....but never local. And everyone was +$20 shipping. Somehow it rubbed me wrong. Knowing the actual shipping cost would be hard-pressed to exceed $5, I guess I just couldn't bring myself to support the dishonesty. If you want $30 for the part, make the price $30!


(these places were not on eBay where I could understand it was a "dodge" of the sales%)