Erratic idle solved

[blaze_away]

Like many on here my Chim has suffered from erratic idle,
Eg after revving it sits at 1600 ish and will not drop to 1000 rpm
At idle will sit anywhere it fancies and moves around.
Adjustment process for setting idle is difficult.

I decided to test for a vacuum leak using a smoke leak detector. Absolutely amazed at how effective it was at revealing.....

This revealed 3 leaks I had no idea I had.
1. A bent valley gasket corner
2. Small leak on stepper motor housing
3. Leaky o ring on an injector

Having fixed all these leaks my Chim now idles spot on 950rpm and revs up freely and immediately drops to idle when you come off the throttle.

All I can say is its a brilliant piece of kit that might help others suffering poor idle control

https://m.youtube.com/watch?v=URRId6fTrGo

[Classic Chim]

Ha, so not all stepper motor problems are the fault of the stepper motor
It was running so sweet the other day you must be very pleased now then.

That’s a great tool you got there

[blaze_away]

Yeah well pleased mate. Just that brake bleed to do now. Will get the hole cut next week.

[Belle427]

I watch a guy on you tube called south main auto that uses these in diagnostics a lot.
Good tools, he’s worth a watch and is quite entertaining, American but still good.

[blitzracing]

Umm --- now let me see.... :-)

https://www.ebay.co.uk/itm/264165071710?chn=ps&amp...

[blaze_away]

blitzracing said:

Umm --- now let me see.... :-)

https://www.ebay.co.uk/itm/264165071710?chn=ps&amp...

.....with a fish tank air pump maybe....

[blitzracing]

They have bellows on the side to puff. My mother used to keep bees and used burning coiled corrugated card to make the smoke. A bit ash heavy for engine use but I see you can get better smoke tablets these days.

[Sir Paolo]

I too found an idle problem was due to an air leak at the stepper motor.
A bit of sealant on the fibre washer cured it.

There was another air leak courtesy of a split in the vacuum advance union at the distributor.

Idles and drives very sweetly now!

[s p a c e m a n]

I suppose its tidier and less dangerous than randomly spraying carb cleaner at parts of the engine

[jojackson4]

s p a c e m a n said:

I suppose its tidier and less dangerous than randomly spraying carb cleaner at parts of the engine

Not as good at cleaning though

[blaze_away]

I did try the carb cleaner spraying but it wasn't precise enough. As the idle was not stable it was difficult to be certain there was a leak let alone say where it was.

The smoke test really pinpointed exactly where the leaks were, and it didn't catch fire on me !!

[SwervinIrvin]

Thanks for the info about the smoke tester, I’ve been struggling with the erratic idle for a bit. I had a bad stepper motor and replaced it with what I hope is a decent one. This morning I checked for leaks with my new smoker and found two that I never would have found without it. After setting the idle she runs perfect now!

[blaze_away]

SwervinIrvin said:

Thanks for the info about the smoke tester, I’ve been struggling with the erratic idle for a bit. I had a bad stepper motor and replaced it with what I hope is a decent one. This morning I checked for leaks with my new smoker and found two that I never would have found without it. After setting the idle she runs perfect now!

Well that's rather neat, glad my woes helped you sort your running issues.

I wonder how many others over time have had similar issues and never really gotten to the root cause ie induction leaks.

[steveo3002]

did you buy the machine in the youtube vid?

id like to check for leaks but put off by the price

[blaze_away]

steveo3002 said:

did you buy the machine in the youtube vid?

id like to check for leaks but put off by the price

The one in the video is the one I used, but it was borrowed from a local garage after I made facebook request for advice on which machine to use.

There are cheaper versions but the accessories with this one mean its easy to find a way to connect it to the induction.