Stalls rather than idles

[rknowles74]

Hi All,

Im after some pointers on where to start fault finding. I have a Nostalgia XK120 replica with the drive train out of a 1988 3.6L XJS (so the AJ6 engine with the round air filter).

I last used the car a couple of weeks ago and it was running fine. I went to start it up yesterday and it will not idle at all. The engine fuel pump primes, the engine starts and the revs go up to 1000 (as normal), but then it stalls immediately. If I put my foot on the accelerator I can keep the car running by pressing it gently. It revs fine with a harder press, but as soon as I take my foot off the accelerator the car just stalls.

Can anyone suggest what the problem may be? I find it strange that the problem just appeared after a couple of weeks in the garage.

The only thoughts I have are that the idle control valve may be stuck closed, but Im not sure how to test it.
I should say that last winter the engine revs would hunt up and down a little when starting from cold, but with the summer weather it stopped doing that.

Thanks
Richard

[davidr]

I think you're starting in the right area. I'd suggest taking the throttle body off and giving it a good clean with carb cleaner making sure that the butterfly is spotless and the idle valve isn't gummed up.
Gloves are essential as its a mucky job and don't use anything abrasive - the wife's toothbrush is ideal!

[poprivet]

Further to Davids advice, after cleaning and setting the throttle body gap, clean and re-set the idle stepper motor, basic info here:
http://www.jag-lovers.org/ebooks/view.p ... ction=10.6

Al

[rknowles74]

Hi all,

I followed the advice above, the throttle body was pretty clean as I cleaned it well when I built the car 3 years ago, but the air gap was a bit small so I opened that up.

The idle control valve was a bit gummy. I had not cleaned that before as I was a bit wary, not really knowing how it worked.

Following the reset instructions I started the car and it sprang to life idling up at 1600 rpm. I left it there to get fully warm. Once the temperature hit 70ish the revs dropped to around 1100.

I then tried to adjust it down to a decent idle - but enliven with the iscv fully screwed in it was still at 900 ish. So I adjusted the throttle butterfly to close up the gap a bit - reasoning that my measurement would not be that accurate.

I've ended up with the iscv about 3/4 turn from closed and idle at about 800. Although the car is probably still a bit warm so I'll give it a go tomorrow for a final adjustment.

Thanks for the help - that's one more part of the car I understand.

But - what is the unit forward of the throttle body in the air hose that feeds air to the iscv? I'd love to understand what that does.

[davidr]

I think that's probably an extra air valve designed to raise the revs when there is extra load on the idling engine caused by the air conditioning compressor.