2.7 engine stalling

[Classic 911]

Hi,

I have a question regarding running a 2.7 engine with CIS. The engine stalls when the car is stopping at red lights and road crossings.

The engine is fully rebuilt.

So I was hoping for some input from the Pelican community

Cheers


Sent from my iPhone using Tapatalk

[fanaudical]

There are lots of potential reasons for this. What year / iteration of CIS do you have? Is this happening when the engine is cold or warm?

I would start with checking ignition: Is timing right, is the advance curve right, plugs clean, wires in good condition, etc.

Following that you can move onto the CIS. Do all the basic pressure tests and report back. Look for vacuum leaks.

[dailydriven911]

Quick fix might be to up the idle I bet you have vac leaks

[EC900]

You didn’t mention your idle RPM’s when coming to a stop vs. parked and idling and if there’s any erratic rpm swings like surges on cold start.

Mine stalled that after I fixed one vacuum leak, drop was down to around 600-700. It’s a simple adjustment to increase the idle speed back to the normal 950 range.
Also worth simply checking battery connection and volts, weak connection could also stall an engine.

[PeteKz]

More info needed. What year car and engine/CIS? How many miles? Is this a new problem? I see from past posts that you rebuilt the engine yourself.

Does it run otherwise normally and at full power? If so, then your ignition is fine. Focus on the CIS. As others have said, set the idle RPM. With the age of CIS systems, there's a high probability that you have intake air leaks. DO you know how to test for those?

[Charles Freeborn]

Go through all the basics of CIS diagnosis. Pressures, filter, accumulator, vac leaks etc. They can be fiddly.

[kach22i]

Originally Posted by Classic 911

Hi,

I have a question regarding running a 2.7 engine with CIS. The engine stalls when the car is stopping at red lights and road crossings.

The engine is fully rebuilt.

So I was hoping for some input from the Pelican community

Cheers


Sent from my iPhone using Tapatalk

Same engine?

https://forums.pelicanparts.com/911-engine-rebuilding-forum/1120136-1975-2-7-cis-engine-not-ideling-when-warm.html#post11709085

Is this phenomena experienced differently on cold verses hot days?

I have to adjust my CO mixture screw in spring and fall sometimes when the weather changes, and suspect vacuum leaks as aggravating things.

If you do get to twittering with things, I found the following 11:00 video starting at the 3:00 mark to be helpful in visualizing what some of these adjustments are doing.

I don't know if the 1.9mm of play is applicable, I'm just saying it is a helpful visualization to a rather blind process of adjustments should you keep the boot on.

I'd really hate to lose an Allen wrench inside of my throttle body so I keep the boot on when doing such an adjustment- just saying. Others may chime in on the proper procedure using actual measurements, gauges, meters and tools verses "by feel" and using one's nose/ears/eyes to figure out if the mixture is right.

Mercedes Ke Jetronic- CO/mixture screw adjustment(air-fuel ratio adjustment) Sensor plate adjustment
https://www.youtube.com/watch?v=ThoatMlKT3k

[proporsche]

well? start with the basics...
1.clean distributor point and set the dwell
2.distributor timing set -on warm engine
3.what is your idle set at?
4.your fuel mix could be too rich...adjust the fuel mix..providing your sensor plate is set correctly
check and report back