Idle Moving By 200 Rpm

[toolie72 67 1 Cars]

Hmmm, cleaned out throttle body,sad,afm etc

Checked all hoses but still have a weird idle

Sits at 900 then up to 1100 then back again-it does it at a constant rate ie 3seconds at 900 then climbs to 1100 sits for 3 seconds then drops down, then goes back up

WTF-cars good other than that-think I might play with ignition timing

Anybody had similar?

Or is the car possessed dundundun

[Anthony 1,003]

Lean the idle mixture out a couple of turns on the AFM (anti-clockwise) and see if that improves matters - you often get hunting when the mixture is too rich.

[steve@cornwall 100]

Mine does similar with lights on. Suspect alternator as battery new and connections good.

[toolie72 67 1 Cars]

Leaned it out, changed coolant sensor, alternators 6months old (new not recon), moved timing, cleaned out sad and hoses, checked for air leaks with carb clean, cleaned out throttle body

Gone round all breather hoses etc clamping them off

 

No bloody difference

 

Come up to a junction she dips to 650 rpm then steadies?!?! To 1000 then 1200 then back again, cycles doing 1000 then 1200

She's a pig cold but sads working

Don't have a clue now

 

Still getting good at left foot braking-arse,feck,waiting for the summer

[toolie72 67 1 Cars]

Changed afm

Same

Starting to rain-bolx to it lol

[GLPoomobile 958]

Worn throttle body

[toolie72 67 1 Cars]

Ha good call-I have a manky spare one anyway I can try-if I can find it

[DamirGTI 342]

My first 205 did this , fixed it by bending the end stop on the dizzy spring (the smaller/weaker spring)

 

Guess the springs loosen tension over the years ..

 

D

Edited February 18, 2017 by DamirGTI

[toolie72 67 1 Cars]

Another good call and again I have a spare (if I can find it)

I moved dizzy but it made no difference to the moving revs-no oil in it, did check

As you say if it's a spring that might explain the fact that the revs rise/fall rhythmically, the timing could be wandering off then coming back

 

No I don't have a timing light-will maybe blag a shot of one

[DamirGTI 342]

If you want to try tensing the dizzy spring , i'll post an picture so that you can see what needs to be done ..

 

There's too much initial anvance built into the dizzy even for std. engine , tensing the weaker spring the idle will be stable and you'll pick a few lost 'horses' also .. ti'll go better for sure .

 

D

[steve@cornwall 100]

I'd certainly be interested

[DamirGTI 342]

Righto , goes like this :

 

Pop this metal cap off :

 

 

And underneath , through the aperture , you'll see the insides of the dizzy springs - spin the shaft and aim for the thin wire spring and it's end stop .

 

Theres two springs inside one is made out of thicker wire and has more slack :

 

 

Other one is made out of thinner wire , and has less slack - this is the one which you need to tense up :

 

 

 

Do this simply by bending the end stop of this "thin wire" spring outwards - to the dizzy body , this is the end stop (spring is missing on the pic !) :

 

 

 

Originally it's like so (also missing the spring on this pic !) :

 

 

 

And this is modified/bent outwards (i bent this one all the way to the limit of touching the dizzy body , cos i had very high compression ratio and i needed all the movement i can take in order to tense the spring) :

 

 

 

Use pliers or simply an screwdriver and bend the end stop outwards as you wish in smaller increments and test drive afterwards or you can bend it all the way till it's near to the dizzy body (but do not bend so that it rubs on the dizzy body cos this spins along with the shaft !)

 

No need to dismantle the dizzy , neither the springs - leave everything as is just work trough the aperture .

By bending the end stop you're putting tension on the spring , and do that just on this thin wire spring , leave the thick one as is .

 

After you've done that , you'll need to re-adjust the timing .. but do not use an timing light , do it on the road by ear (an search here will reveal this method how to) .

 

Results from my experience : the idle will be rock stable without waving up/down , it'll accelerate better and will pick up some power/torque too .

 

Try and see if it works for you !

(ps : this is how the H&H guys are doing them when re-curving dizzy with std. springs)

(if for some reasons you do not like this - just bend the end stop back inside till it's parallel to the dizzy body)

 

D

Edited February 18, 2017 by DamirGTI

[steve@cornwall 100]

Very interesting and hadn't come across this before. Will have a try. Thanks Damir

[DamirGTI 342]

Yes this definitely isn't 'an bools*it' modification .. it does work !

 

Me thinks that the dizzy advance mechanism loosen up a bit during the years of wear and tear , and todays unleaded petrol is different too so tensing the weaker initial spring makes it for the slack within the dizzy stabilising the idle and restores some power/torqe .

 

D

[toolie72 67 1 Cars]

You know what

It only blooming works!!!!

 

Countless other issues to sort out (as usual) but idles steady

Hardest bit was getting the metal cap off then retrieving it when it went ping

Only moved it about half the distance available so probably 2mm on spring so impressed it made a difference

 

Thank you very much Damir

Cheers

[DamirGTI 342]

Happy to hear it did the trick !

 

D