2.4E engine, strange "bing" at idle

[peter 911 TS]

have strange unfamiliar “ping” or “bing” sound occurring in my 2.4E engine from 1972.

The 'bings' escalate in cadence as the engine gets to operating temperature, after starting up, and after driving for a while.

The engine revs seems to dip just slightly after each ping –but not enough to show on the rev. counter. As though as if there’s an occasional non-detonation..

When driving the 'bings' doesn’t seem to occur…

The engine pulls very solid and strong acceleration, but more roughly at cruising below 3000 rpm, or accelerating slowly.

Any ideas what causes this?

Thanks in advance
Peter

[Flieger]

Welcome to the forum. Please post a picture of your car and engine and add them to your profile/signature when you get the chance.

My guess would be a collapsed timing chain tensioner. Have yours been updated to the oil pressure-fed model?

[peter 911 TS]

thanks for the advice... it seems it's throttle bodies letting in "false air" though.

will post pics when I get a chance.

best,
peter

[Jeff Higgins]

They will make that sound when the synchronization is off. Your assessment of "false air" is the "binging" stack pulling more or less air than the rest at idle. As you have noticed, this goes away completely when the throttles open, either under load or as rpm's increase. Classic symptom of poor synchronization.

Have you performed CMA on your injection system? If not, that would be the first thing to do. You can find a copy in the Pelican archives, or the tech info section, or something like that. I know there is a copy here somewhere. Search and ye shall find.

[Roland911]

Hi Jeff,

thks. for solving the problems with the "white and black" srews.....
After 4 years of studying everything about the adjustment of the MFI that should solve my problem: too lean during part load.
Even the German experts couldn't help.
How can I thank you?
Next time when you are in Germany you will get beers for free.

Coming to the other "bing" problem.
I had the same problem and coulndn't find the reason.
After 2 years I dicovered that the filter in the trunk did not allow enough gasoline fow.
If you give full throttle no problems as the MFI is apparently sucking gasoline from the pipe which is going back to the trunk.
After renewing all the problem with the "bings" was gone.
Not shure if that is your promlem but if I were you I would check it anyway.
And: don't clean it, better is to replace.

Roland