High idle speed/tickover problem !

[epipete]

Collected car today following repair to turbo, etc, etc as described elsewhere.

All is good, however she seems to be over revving when in neutral, at about 2000 rpm, as soon as she is under load the revs return to where they see expected. More alarmingly, not only is she over revving but also rhythmically, possibly at normal breathing rate she tied from a high 2000 rpm to 3000 rm and then down to 2000 again and repeat! Perhaps she should be called Christine!

Any ideas?

Pete

[Enright]

Collected car today following repair to turbo, etc, etc as described elsewhere.

All is good, however she seems to be over revving when in neutral, at about 2000 rpm, as soon as she is under load the revs return to where they see expected. More alarmingly, not only is she over revving but also rhythmically, possibly at normal breathing rate she tied from a high 2000 rpm to 3000 rm and then down to 2000 again and repeat! Perhaps she should be called Christine!

Any ideas?

Pete

Pete,
Call me pedantic but I wouldn’t have said that this was “over-revving” as such. I believe over-revving happens when YOU over- rev the engine beyond its designed rev limit – e.g. flooring it in neutral, or selecting too low a gear when changing down.
Obviously those results are EVEN less pretty than what you’re already experiencing, but this sounds much more like a straighforward high idle speed problem to me.
Sorry but I haven’t time to go searching through lots of other threads/posts to see what other work has been carried out, however to me it sounds like something has been put back together incorrectly and is potentially leaking either air or fuel into the system.
Can you advise which thread details the "other work" that’s been done? Seeing as this definition is misleading and there’s no reference to what’s been done before, I think it would be best to move it to a more user-friendly location, which I’m quite happy to do. You will then probably get more educated replies which help you sort out your problem. I just need a clue where. No offence intended - I just think that you'll get more constructive responses if the problem is defined properly and the background to it is immediately accessible to those who you are asking for help.
As a starter though, I would suggest using a piece of hose as a stethoscope to try to find the air leak in the intake system, or if you can, block the intake hose and try to get some pressure into the system so that you can trace the hiss. It worked for me when I folded an intake gasket back on itself.

[epipete]

Neil,

Thanks for the above, I was trying to move on from my previous thread: viewtopic.php?f=31&t=22784&p=294933#p294933. as I think that is pretty well exhausted and this issue is, I believe, unrelated.

I would not wish you to go searching on my behalf, it is time consuming and is something that I should, and will, take responsibility for myself, what I was requesting of our fellow members is 'a pointer' should any one have had such a similar problem hence posting under 'Problems - need help' and the title 'Over revving' and I read your definition with interest.

Despite my defending myself above, your advice to search/listen for air has paid dividends it seems that I am missing a bleed screw in the Primary Throttle Body, how this has come out I cannot imagine. Does anyone know what it is I need to replace and where I might get one.

I've bunged the hole with a red plastic plug in the interim pending a proper component. The pic needs turning 90* !!!

[GeoffSmith]

Any ideas?

Air leak, but I guess I'm a bit late.... I had it once (random leak from the dreaded rubber elbow) and tickover was a lot higher than it should have been, but maybe because the leak kept self-sealing, it was more a case of a meandering tickover but it did exceed 2000RPM at times when cold which is obviously revving over the target idle.

[epipete]

The missing item are:

Throttle By-pass screw A100E6431S, &
Anti Tamper plug A100E6430S

Does anyone know if the screw is just a standard threaded 'bung'?

[RayD]

Hi Pete,

Normally you would be directed here to solve your problem, but you would have come unstuck when you found the adjustment screw missing.

It's a timely reminder for others to make sure they have something stopping the screw coming out completely.

If you haven't already have a good look round the engine bay just in case it's lodged somewhere ... other than that you need someone to remove the screw from a spare to see what it looks like

Ray

Edit ... Been out to the car to have a look and hadn't noticed the two extra posts.

[GeoffSmith]

It's tapered (part #55) but anything has got to be better than nothing Pete.

[epipete]

Thanks guys,

Typical! SJs list the Anti tamper plug (88 pence) but not the darned Screw.

Your quite right Geoff anything is better than nothing hence my red plug, but at least it matches the Samcos!

[epipete]

Thanks Ray,

Anyone got a photo?

[GeoffSmith]

Giz a chance!

Bugger. It's not as easy as it seemed:

Idle adjust screw x640.jpg

... and it's the old M12x1.0 banjo/wheel bolt thread again.

Must go and replace my idle screw before I forget how many turns......

[epipete]

Well that's a nifty piece of kit! I wonder if it is generic ie: used in any other vehicles?

I note there is an entire throttle assy on eBay but it seems a little excessive to spend £50 squids just to get a screw no matter how exotic!

[Fredjohn]

Would have thought £50 for a screw pretty good value myself

If non of the Lotus specialists have one, alternatively try a hydraulics suppliers such as Pirtek or GTSS or similar.

GTSS website: http://www.industrialsupplyalliance.com/ebooks/gtss/

[RayD]

One and a half turns out Geoff,

Ray

[Rob P]

Pete, I have just checked the garage and I have an old throttle body I bought when I needed a TPS unit, there is one of these Tapered Screws in place, I'm happy to send it over to you if you still need it as it's just sitting in the throttle body doing nothing

Drop me a PM with your address and I'll pop the screw in the post for you. I know how frustrating it can be to have issues and not have the car on the road

[epipete]

Rob, you are a very decent man, thank you. You have a pm.

[Enright]

Glad this discussion has helped to not only trace the problem, but to sort it out too.
I'm going to re-name the thread "High idle speed/tickover problem" as it's more relevant to the symptoms described - this may help others in future searches.

[epipete]

Thank you Neil, that is a good title.

I did google 'over revving' (because I am a pedant ) it seems we may both be right depending on whether its used as a verb or a noun.

[epipete]

Thanks to Rob I am now sorted for this 'odd' screw and it is now incorporated correctly into the throttle body.

It is extremely well engineered insomuch as it screws in almost with no friction and, although I've never heard of anyone else losing theirs, I can certainly see why Lotus designed an Anti Tamper Plug to both hold it in position and to stop it working loose. I think I'd better order one from SJ's

Geoff, I owe you a donation to the kitty when I see you next!

Pete

[muley]

..or just put a dollop of silicone sealant on top of it. You can always pull that out later if need be.



Jim

[epipete]

..or just put a dollop of silicone sealant on top of it. You can always pull that out later if need be.



Jim

Indeed, a very good point. I was just too busy listening to Murray lose to engage my brain