911 3.0 pops & backfires while running through intake
 

any help would be appreciated.
when i parked my 3.0 6-months ago it ran very good and strong. While parked I replaced the fuel filter, gas tank and fuel lines. I also rebuilt the fuel distributor being very careful while doing it. I took it apart about 4-years ago and did the same thing. valves are adjusted right. EVERYTHING on engine hoses to components to seals to gaskets are rebuilt or new. Has MSD unit and did not touch that as it was running fine when stored. Injectors are clean. New spark plugs, coil etc. as when shut down and stored. Fuel system is clean from tank to injectors.
Now with that engine was starting and running the best ever when shut down for storage. Now it will start right up but kills. I can keep it running with foot throttle but will not idle on its own no matter how warm it gets. All the while it pops occasionally out of intake. Fuel mixture is on the rich side and not lean and was running like a tiger when stored.

It may be spark related due to the pop. It starts too sharp and fast to be fuel related.

Well what do you guys think???

antares
fatnwide

It sounds like either your lambda brain is dead or your mixture adjustment screw has migrated to an unrunable mix. Try this to eliminate mixture. Remove the air box cover. there should an aluminum arm in the back of the air box. Pulling down on it will lean out the mix, pushing up on it will enrichen it. have one of your friends start the car and hold the car 1000 rpm. Then using the weight of your finger, pull down on the lever, at some point it will start to stumble. If it happens with very little movement, then you are running far too rich and needs to be leaned out. And of course if it seems that you can not get the car to stumble by enriching it then you are running far too lean. And besides it doesn't hurt to check your mix.

Did your new "everything" include a new AAR and WUR? Sometimes even new WURs can be out of spec. Try checking your control and fuel pressures.

It screams ignition. Howz about that MSD? I've read too many threads about them. There was one the other day with very similar symptoms to yours. Still got your original CDI?

ianc

Edited to say: Antares, I'm in San Rafael. Could give you a hand in a week or two. PM me if you're stuck.

ianc