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My engine idles at 1800 rpm when warm. I can bring the revs down with the clutch, but they return once I move away and come to a stop again.

I've done a search and found plenty of info, but only for MFI / CIS cars. Mine is a carburated 2.4.

Can anyone tell me where I can start-off looking?

Hi Jamie: was it O.K., or has it always done it?

Was O.K.: Make sure your hand throttle is down, and not holding the throttle open. Check timing (if the advance mech. plays up it can leave the timing out which can affect the revs). You can do this by putting a timing light on the car and taking it from idle to 3-4000 revs and back down: if the timing jumps at any point rather than advancing / retarding evenly that may be the problem, particularly if it tends to stich when returning to idle. My car had a worn dizzy spindle which kept changing the dwell angle at idle, which in turn affected the timing, and therefore the idle: if you stopped the engine and restarted it would idle fine, as soon as you touched anything, the idle would shoot back up.

Check that nothing looks odd around the linkages (like one of the throttle stop screws being completely different from the other or something jammed on the linkage). Finally make sure that the main accelerator linkage is not jammed somewhere.

Basically if you look at the throttle stop screws, if they are not touching their stops, you've got a problem with the linkages somewhere.

Never been O.K.? You will have to go through the whole setting up process. I won't go into it now but basically you would need to check: timing and valve clearances. Then you would do a basic carb set-up, and then go back round and do a fine tune. If this failed to fix it, then you would start hunting for manifold air leaks, leaking throttle spindles etc etc.

Start off with the real basics: generally the carbs are fairly reliable, and it's much more likely to be something simple, or just muppetry .

My engine idles at 1800 rpm when warm

know the feeling..

As you may have read I can't get my idle below 1400, my problem is leaky spindles. Soon to be replaced by an EFI system

May be easy to get the spindles and bushes replaced, but that wouldn't be as much fun

Go with everything Barry said. Then fit EFI

My site has all you need to know (or don't) about Zeniths, so have a read. It may be of some help.

Hi Gary - great website - exactly what I have been searching for! Now bookmarked. EFI definitely out of my price range for the time being since I kind of maxed-out for now on buying the car.

Cheers for the advice Barry - I don't really know if it was OK, or whether it has always done it as I only just got the car. Until two days ago, the furthest it had ever been was up and down 200yds of track. Then it went for a drive to and from it's MOT, and now I notice the idle problem!

The hand throttle is definitely down, so I will take a look at the stop-screws.

It also just occurred to me that the hand-throttle line doesn't really do much when moved, so could be stuck or rusty. I'll check to see if it moves freely at the engine end. If the line worked properly and engine was idling at 1800, should pulling it up increase the idle even more? Because it doesn't...

Hi Jamie: it's probably a good sign that the hand throtle doesn't make a difference: hopefully, as you say, it's just got stuck somewhere.

Good place to start anyway .

Hi,

Unless I'm mistaken (it wouldn't be the first time ) the hand throttle works directly on the throttle linkage push (pull?) rod?

I guess the little clamp it pushes against has moved or come loose. Once you get your idle down you'll need it again for those cold morning starts

Ohhh...

This all makes sense - they run through the same part of the car, at least.

It's a bit frustrating - I live in East London and the car is at my parents place on the Kent / Surrey border, so I can't just pop outside and fiddle with it. It's a good job really since I am supposed to be doing some work today, but still frustrating. Might go over there tomorrow and have a play.

Barry wrote:Check that nothing looks odd around the linkages (like one of the throttle stop screws being completely different from the other or something jammed on the linkage). Finally make sure that the main accelerator linkage is not jammed somewhere. Basically if you look at the throttle stop screws, if they are not touching their stops, you've got a problem with the linkages somewhere.

I'd say Barry is right on the money there

Aww shucks .

It'll probably turn out to be a flux-capacitor problem now .