Another high idle thread - how-to on butterfly plate springs?

[jawn101]

Hey folks, sorry for the long, long delay on this thread but wanted to share some new insights for anyone interested. Clint and I checked the car out with a smoke machine today and found three vacuum leaks - injector #5 wasn’t sealing properly (I replaced all the seals and this one seems to just be bad), the ISM pipe, and... the top of the ISM itself, as I suspected. If you remember, I had observed that pressing on the top of the ISM changed the idle characteristics. Well, check out this video.

https://youtu.be/7q_ZVpHPNzI

We temporarily “fixed” it with some superglue and RTV but it’s sloppy and I haven’t come this far to have a literally glued together idle motor Off to DeloreanGo with me! Will report back with anything further once I get the replacement injector seal and ISM installed.

I’m also considering Dave M’s solid state idle controller, but that’ll be a phase 2 if anything.

[bytes311]

I discovered I had the same exact leak a month ago. I replaced the stock ISM with a used Volvo unit. The Volvo unit is smaller and runs on less current.

[Elvis]

...

I remember ages ago Elvis was quite hot on the notion of cleaning and maintaining the decel valves on the butterfly plates. I know that these might stick slightly and cause a higher idle.
...

I never talked about these valves. I am always pointing on the complete butterfly assembly which is often not fully closing, especially with vakuum applied.


But seems like you found a new spot for vakuum leaks - good job :-)

[jawn101]

I never talked about these valves. I am always pointing on the complete butterfly assembly which is often not fully closing, especially with vakuum applied.


But seems like you found a new spot for vakuum leaks - good job :-)

Ah, he lives! I still think there may be some aspect of the throttle plates not closing completely too, but I’m trying to change as few things as possible at a time to be sure I find the real issue. The ISM was clearly damaged so I’ll drop a new one in and then look for the next problem.

I discovered I had the same exact leak a month ago. I replaced the stock ISM with a used Volvo unit. The Volvo unit is smaller and runs on less current.

Yeah, the one that DeLorean Go sells is much smaller as well. I’m not sure what the crossover point is for it but I’ve come to trust their choices over there, and it was significantly cheaper than a NOS model.

https://www.deloreango.com/us/idle-s...tor-motor.html

[Chris 16409]

It's best to find a genuine German Bosch Idle Speed Motor. Most usually sell unbranded units. The reliability of these are dubious at best.

02AF1DB7-277F-45B3-A367-EE6C282FE28E.jpg

[jawn101]

Installed the new idle motor from DeLorean Go today (BTW, those folks are just incredible - they ship to me in CA faster from the UK than Amazon, and there’s an Amazon warehouse in walking distance!) and it’s made a huge difference.

This is the motor they sent, with the old one:

And here it is installed:



It’s definitely smaller than stock, and looks a little weird because I’m used to the old one, but it works great. Even after a 20 minute drive in the burning 100-degree heat, the idle was a perfect 750 whether the A/C was on or off



But now the issue is the leaky seal around injector #5. That was another obvious vacuum leak when we smoke tested the motor, and even with brand new seals it’s very tenuous. I’ll start another thread for that...