1977 stock coupe runs then dies

[Wade Nelson]

>The AAR is still dumping all kinds of extra air into your manifold, creating a super lean mixture, which could, I suppose, in theory, kill the car and then make it hard to start again 'til it's cooled down.

Wrong, wrong, wrong.

The AAR picks up air downstream from the Mass Airflow sensor. That means that ALL air passing through it has been metered. The ECM will inject fuel to match the amount of air metered. So the AAR is not just "dumping all kinds of extra air" and making the engine run lean.

When the system is working AS designed, not only is the MAF adding fuel to accompany any air passing through it, and later the AAR, but the Thermotyme system is DOUBLY enriching the charge since both thermotyme and AAR should both only be flowing during the first 30-60 seconds after startup.

[LeonV]

>The AAR is still dumping all kinds of extra air into your manifold, creating a super lean mixture, which could, I suppose, in theory, kill the car and then make it hard to start again 'til it's cooled down.

Wrong, wrong, wrong.

The AAR picks up air downstream from the Mass Airflow sensor. That means that ALL air passing through it has been metered. The ECM will inject fuel to match the amount of air metered. So the AAR is not just "dumping all kinds of extra air" and making the engine run lean.

When the system is working AS designed, not only is the MAF adding fuel to accompany any air passing through it, and later the AAR, but the Thermotyme system is DOUBLY enriching the charge since both thermotyme and AAR should both only be flowing during the first 30-60 seconds after startup.

There is no MAF on these cars, it's an AFM. Blue posted a great diagram on this site relating to how much enrichment each device provides and where it comes on and off. Found it in his tech tips site: http://atlanticz.ca/zclub/techtips/efisystem/overview.html

BTW, that post was 2 years old...

[Wade Nelson]

thanks for the link. That's a fabulous diagram and a very good overview.

Re: AFM vs. MAF --- air flowing through either one will get measured and fuel metered for it. My point was that a wide open AAR isn't going to enlean the charge.

I realized the post was 2 years old, but figure correcting the archive of info here, a real treasure trove, is just as important as correcting current posts.