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High idle - XJR

Posts: 184
Joined: Thu Jul 10, 2008 9:21 pm
Location: Hitchin

High idle - XJR

Postby pugboyracer » Thu Feb 23, 2017 11:43 am

Hi guys,

My XJR has been good as gold for 2000 odd miles now, but she's started to develop a high idle. It's not all the time, but is quite often, when stopping at lights etc. Usually idle in drive is around 750rpm, but it can stay around 1000rpm on occasions.

There's also a funny sensation of "surging" sometimes, when lifting off the throttle at speed. I swear I can see the revs climbing slightly, even though I'm off the gas.

Beyond this, the car is driving great, took it up to Birmingham and back last weekend and it performed fabulously.

Any hints of where to look would be good. I suppose it feels like the throttle isn't quite closing, so some advice on where to check the throttle cable would help. I suppose I should also think about inspecting the throttle body too, but that means mucking around removing the supercharger... :(
1996 XJR6

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Posts: 28789
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Location: Kirton, nr Boston, Lincolnshire

Re: High idle - XJR

Postby naki_k » Thu Feb 23, 2017 11:54 am

It may even be a combination of things.

Clean out the idle valve and throttle body.
The throttle position sensors can play up too. I replaced the one on my 300 manual.

Clearly a bigger job on a S/C model.
May be worth putting a code reader on it to check for fault codes too. As a precaution.
88 3.6 XJ6 PDH/CEM
90 Range Rover Vogue SE 3.9 V8 LPG
91 4.0 XJ6 Manual
92 4.0 XJR Manual
92 4.0 XJR
93 3.2s - 4.0 Manual conv
93 4.0 Sovereign
93 6.0 XJ81 DD6 x2
93 6.0 XJ81 XJ12
94 4.0 XJR
94 4.0 Daimler
96 4.0 X306 XJR
96 4.0 X300 D6
97 4.0 X300 Sport Manual
2000 LR Discovery ES TD5 A
Breaking 40/ 300