Funky idle

[MML]

My car has started misbehaving again... I have a recurring problem where the idle goes up to around 1700 rpm; you have to tap the accelerator a couple of times to bring it back down to the normal 700 or so.

I've seen it mentioned before that sticking throttle cables can cause this, but I just wanted to post the video showing my own particular situation. Any advice would be welcome!

I've only had the car out a handful of times since wakening it from its winter slumber a couple of months ago, it was fine up until this happened the other evening. It started doing it after about an hour's driving.

It did the same last year as well, it only happened occasionally though.


https://www.youtube.com/watch?v=f6kfZkxX9DI

[AugustneverEnds]

Check the hoses connected to the idle speed motor. Check the electric connector on the ISM. Is the screw on the end of the throttle arm pressing the idle speed microswitch? Are the deceleration springs in the butterfly valve fully closing the valve? (this thing: http://store.delorean.com/p-6395-butterfly-assy.aspx) I would start with these things

[Ratrace427]

It's the idle switch. Don't get it confused with the wide open throttle switch. Give it a clean and it should be ok. Might need a little adjustment

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[David T]

Could be a couple of things. First make sure the throttle cable is not sticking and returning ALL the way to idle. Lubricate it as per the recall. Next make sure, when the throttle is at idle it "sets" (operates) the idle switch, activating the idle motor system. Finally, inspect the "Quadrant Link". It is the tiny bar with ball sockets on each end between the throttle arm and the throttle spool. The sockets get worn and introduce a lot of play preventing the throttle arm from positively tripping the idle switch reliably. Another thing that could be happening is the throttle spool is stiff. The grease gets old and makes it difficult to move freely. The cure is to take it all apart, clean all of the parts, lubricate and reassemble. Careful, there are a couple of springs in there and the parts are fragile and can break if you force them. Last, make sure the carpet and/or the floor mats are not interfering with the accelerator pedal preventing it from returning all the way.

[dn010]

An easy way to tell if it's the quadrant link is when it's idling extremely high, go to the motor and manually push the spool and link fully closed with your hand. If it goes back to a normal idle then you know where your problem is. Back on my original motor days, I actually installed a spring on the link to the closing plate to always bring the throttle fully closed.


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[MML]

Hi fellas, many thanks for the advice.
We only got a quick look at it today. In the 15-20 minutes the car was running, it idled at the normal 700-ish mark.
What we did notice was, the little linkage arm doesn't seem to have any excess play, and the idle switch does seem to be operating properly. All the other suggestions will still need to be checked. I plan to disassemble everything at some stage and thoroughly clean it all... that engine bay seems to attract dirt and dust like a magnet!

Here's a quick video.


https://www.youtube.com/watch?v=apCNHOJDDLY&feature=youtu.be

[MML]

Pics of the spool area.
What is that little white switch, out of curiosity? Doesn't seem to be in the parts manual.

51206

51207

[Bitsyncmaster]

Pics of the spool area.
What is that little white switch, out of curiosity? Doesn't seem to be in the parts manual.

51206

51207

The white switch is the wide open throttle (WOT). When pressed it puts the lambda into a fixed 60% duty cycle which would run the mixture richer if your mixture is adjusted correctly.

Note, you should have a rubber cap "seal" on the end of the throttle cable housing to prevent water from getting in the cable and freezing.

[Ratrace427]

Is your throttle cable ok? Looks like it is busted..

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[dn010]

? I don't see where it's mention that it is broken. Even if it is, all you need is to buy the inner cable, takes minutes to remove the old one and run the new one. I never had the rubber cap on mine and never had an issue while living in New York with it freezing but that too should be a simple fix.


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[Kukem]

Had issues with mine as well lately. What you are describing sounds like the throttle cable is coming out of the guide on the spool and laying just above instead of settling back in the channel. This would cause the throttle to still be giving gas and a high idle. Everyone else has great suggestions but it may be as simple an issue as that. David T mentioned the lubrication for the line. Just a thought, especiallysince it only happens every once in a while and takes a few taps of the gas to sort out.

[MML]

Thanks for the comments again guys.
Just a followup... at the weekend I did about 8 hours worth of driving across 2 days, and the problem didn't reoccur. That's not to say it's sorted itself though! :p

I'll keep a close eye on it, and see what happens...