Inherited a SC hotrod, need idle help

mdowell · 04-22-2019, 07:50 AM

Hello everyone,

My uncle was a long-time club member, mechanic, and racer. He died recently of cancer, but before he passed I was able to purchase his beautiful '78 backdated 911 with a 3.6 ('90) that has a '95 intake and computer. The car runs perfectly except for one issue that plagued him the last few years and I was hoping this forum could help.

It idles fine at startup, starts, runs great, but half the time when you put the clutch in while driving, it kills. The other half of the time the idle bounces low (50-100?) then recovers.

A local mechanic I spoke with believes there should be an idle bypass valve installed to go around the throttle body, but isn't that what the ICV does? I have looked for a part like that but can't find anything.

The ICV is clean, the intake is clean... any thoughts? Thanks for any help.

wildcat077 · wildcat077's Garage

I've got a 95 3.6 in my 89 and i heard things about the engine stalling when coming to a stop and so on if you changed the dual mass flywheel , anyhow i have a Kennedy lightweight flywheel and a Steve Wong chip that according to him eliminates those issues.
Might be something to look into if you have a lightweight flywheel ,as it worked for my car.

Just a thought ...

mdowell · 10:59 AM

Thanks Phil,

It does have a lightweight flywheel, but I don't know if the chip has been replaced. I will pull the cover off of the unit and take a peek.

Edit: Virgin ECU and chip.

wildcat077 · wildcat077's Garage

Give Steve a call and explain your issue , he takes the time to talk to his customers and will be honest enough to tell you if he can help you or not.
I think he addresses the lightweight flywheel stalling issue on his website !

ADDvanced · ADDvanced's Garage

I'm sorry about your uncle. Car seems epic.

offroader1006 · offroader1006's Garage

This is an air metering issue.

It could be a problem with the MAF, an intake leak or an issue with the controller's programming/ability to react to the decelerating air when the load is rapidly decreased.

Have you tried to disconnect the battery and let the computer revert to the base settings and relearn the throttle opening?

You may need to monitor the MAF vs load and idle to see if your readings are within range. If they are, it could be an issue with the tune that is getting the ICV operation incorrect.

Dan J · 04-22-2019, 05:00 PM

Contact Steve Wong he has chips that address this very common issues
Cool car though we need pictures!

Duc Hunter · Duc Hunter's Garage

I have a 3.6 with the Steve Wong Chip design for a lightweight flywheel. Steve was absolutely wonderful helping me out through some issues getting the engine running, which is in my 1975 911 S hotrod. The car runs fabulously, although it still does stall on occasion coming to a stop light. This is especially apparent when I’m running my electronic air conditioning. By mass airflow meter was messed with as we were trying to get the car running and I believe that is part of the issue, as I cannot locate a vacuum leak. Point being step one would be called Steve, and simultaneously look for a vacuum leaks. Those will be the only two things I could think of

mdowell · 04-23-2019, 05:09 AM

Thanks everyone. I talked with Steve and he clearly laid out the reasons why the lightweight flywheel and the cup cams are starving the engine during the rapid RPM loss causing the stalling. Ordered a custom chip, will let you know how it goes.

Thanks again.

piscator · 04-23-2019, 06:54 AM

It seems the idle help you got was not, idle. But the guys on this forum rarely are! :-)

Bob Kontak · Bob Kontak's Garage

Quote:

Originally Posted by mdowell

Thanks everyone. I talked with Steve and he clearly laid out the reasons why the lightweight flywheel and the cup cams are starving the engine during the rapid RPM loss causing the stalling. Ordered a custom chip, will let you know how it goes.

Has to feel good having a pro tell you THIS is what your problem is and provide a solution.

I can roughly appreciate the root cause once you stated what SW said but I would be clueless as to a remedy.

Hope this works out well.

mdowell · 05-04-2019, 10:58 AM

Quick update, I installed the chip this morning and so far so good. Tried to stall it for a 20 minute drive and I could not. I think the SW chip fixed it! Going on a long drive tomorrow, will mention if we have any issues. Thanks everyone.

mdowell · 06-10-2019, 09:49 AM

Another update for anyone searching for this issue.

After the chip was installed, I had an issue with the idle "hunting" or "surging". After the engine warmed up, when I put the clutch it, the engine would go up to 3-4k, then dip to 200, back and forth. It was annoying/embarrassing as at a stop sign it sounded like I was revving the engine.

I worked with Steve Wong to solve it, he had me check a bunch of things and finally we adjusted the idle control valve (as he mentioned this can happen from too much fuel) to close the valve (about 1 millimeter) and that has solved it so far.