Author Topic: Hunting idle, sticky throttle problem. found the problem  (Read 1563 times)

Offline z3i

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Hunting idle, sticky throttle problem. found the problem
« on: October 28, 2012, 09:03:13 pm »
Have been reading on here loads as my car keeps hunting an idle and was getting very annoying
read through masses of posts, but no one ever found the problem and just delt with the horrible idle

The problem is when you let off the throttle gently it closes the butterfly but sticks about 1mm and doesnt quite touch the microswitch to say the throttle is fully closed and confuses the ecu so it hunts an idle

people where saying its to do with the larger throttle body, it isnt as mine is standard and does it
if you start your engine open the throttle by hand and then close it gently (it will start hunting) it will look fully closed, but if you push it about another 1mm you can here it clicking the microswitch and as soon as it does the car idles normally.
i thought i would post this as i dont know if any solution came up and apparantly its common on g40's?
im gonna strip mine apart and rebuild it, will take photos and post how to do it. hopefully rebuilding and lubing everything up after 112000 miles should stop it from sticking
hope this helps Taylor
« Last Edit: October 28, 2012, 09:13:48 pm by z3i »

Offline Justin14100

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Re: Hunting idle, sticky throttle problem. found the problem
« Reply #1 on: October 29, 2012, 03:30:01 pm »
If you remove the screws holding the butterfly in you won't be able to get them back in, they're tapered so it may also damage the shaft too. Sounds like the nut holding the mechanism is too tight. Take it off, add some loctite and then tighten it up until its tight enough to hold it together, but not too tight that it makes the mechanism overly stiff.

Offline Yoof

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Re: Hunting idle, sticky throttle problem. found the problem
« Reply #2 on: October 29, 2012, 04:01:09 pm »
Idle switch is a common problem- and well documented!

The other issue with the 51mm bodies is the butterfly chamfer on the edges sometimes doesn't provide an adequate seal with the throttle bore, or the shaft binds slightly with the machined housing, or the return springs are full of crap, or the idle switch doesn't engage.

Either way, digifant will try to control idle speed by retarding/advancing the ignition timing, and can get stuck in a loop (hence the hunting), usually solved with a blip of the pedal.

Vacuum leaks post throttle butterfly also have similar symptoms, injector o-rings are a favourite here.

Offline z3i

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Re: Hunting idle, sticky throttle problem. found the problem
« Reply #3 on: October 29, 2012, 07:18:55 pm »
Sounds like there are many problems that produce the hunting idle

Blipping the throttle stops the problem as it snaps the throttle shut with more force, opposed to slowly edging forward in traffic and coming off the throttle slowly

thanks for that justin, would have been embarasing :P

Was also thinking the springs may have lost some of there tension over 21 years and 112000 miles. so hasnt got the strength to close it that final bit (when the spring would be under the least amount of tension anyway)

Im gonna strip it this weekend, so will let you all know off my find :)
Taylor


Offline z3i

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Re: Hunting idle, sticky throttle problem. found the problem
« Reply #4 on: October 29, 2012, 07:24:49 pm »
Most people have a boost/vac gauge on thier g40 would be easy to check for a vac leak.
at normal idle there should around 18hg - 21hg of vacuum steady, a vacuum leak would read around 14hg steady or under depending on how big the leak is

just thought it would be an easy way to check, altough saying that most of the £50 gauges arnt that accurate as i found, my boost gauge is 2-4 psi out when i checked it with a decent vac/pressure gauge
Taylor

Offline Justin14100

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Re: Hunting idle, sticky throttle problem. found the problem
« Reply #5 on: October 30, 2012, 02:05:45 am »
If you strip it down a bit, clean up all the shite off the washers, blade washers, plastic parts and springs you get loads of tension back. Some I've had are so so covered in grime; some of it the PTFE people spray into the charger, most of it insane amounts of road grime / oil thats accumulated over 20 years). A good spray of WD40 helps too.

Offline z3i

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Re: Hunting idle, sticky throttle problem. found the problem
« Reply #6 on: November 17, 2012, 06:44:37 pm »
Hi peeps, sorry i haven't updated this, was very ill for a weekend and after that have been so busy rewiring the car and welding rust holes Ive found. will get round to it as soon as and post some pictures
sorry again
regards Taylor