Won't idle when warm

Still a few bugs in the 72 911E running a stock mechanical fuel injection. When I first start it when the engine is cold runs great, idles great. After it has warmed up past 170 degrees the damn thing will not idle. It also pops thru the air intakes. However it stills runs great above 2000 rpm. Let it cool down and it runs great again until it warms back up. Any suggestions? Thanks in advance.

Kurt
72 911E

Hi Kurt. Nice car!

Sounds like you're having fun with the fantastic MFI system. Don't let it beat you. It CAN me made to work properly!

Best start is to do some research. Download all the Pelican tech articles on the system. Lee Rice's stuff was particularly useful to me as he boils down all the factory info into easily digestable pieces. Back this up with a cover to cover reading of the factory manual "Measure, Check, Adjust" or something like that.
You may be able to solve your own problem then.
I think that owners of MFI cars have two choices:

1- send them off to an 'expert' every time something goes wrong.

2- take the time to learn the system. All the info is now at hand, and in my opinion, getting hold of that is the hardest part.

Depending on how mechanical you are, it's reasonably straight foward. You need to be methodical. If you're not then you will make mistakes. Write everything you change down so you can undo it if it's a disaster!

Your particular problem may be related to the warm up thermostat. Do a search on this BBS- there has been plenty of talk on what to look out for and what to fix with this item. That's the easy bit to repair so do that first.

Good advice: Listen to what 'Early S Man' (Warren) has to say about MFI. He's been tinkering with it for more years than most mechanics!

Good luck. Get back to us when you've had a look!



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'72 911 TE

Kurt,

I own a 73T, and I would have to say that you need to check the thermostat on your MFI rack, along with your warm up regulator(black box on the left side of the engine). The regulator has a flap that is supposed to close when a certain temperature is reached. This flap closes off the direction of exhaust heat into the intakes. Our cars run a leaner fuel mixture once they warm up, so that explains the popping(thanks Matt!). I had the same problem. I removed the discs from the thermostat and cleaned them. I also soaked my injectors in cleaning solution. I bought a synchrometer too. This tool measures the amount of air going into each intake stack. I messed around with the part load mix screw, and also the idle load mix screw.

I recommend you read the "Check, Measure, and Adjust" manual. It is an excellent place to start.

Bill

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William Armentrout
1973 911T
2.7 carerra rs specs
www.geocities.com/william_armentrout

EUREKA!!!!!! Mucho thanks to Bill Armentrout and Matt Smith for their helpful suggestions. I follwed the "Check, Measure, Adjust" instructions and it now idles fairly well and runs strong. This weekend I hope to work the rest of the bugs out and make the final adjustments. Thanks again!

Good news Kurt. It's great when you nail the problem and it goes as it should again.

Hey Bill, does this mean we're the new MFI Gurus?? hahahaha! Watch out Warren!!

Just kidding of course. Like I said, the best way to get a handle on the system is by reading lots and having a go. Just like any 911 job really....

And use this board if you get stuck!

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'72 911 TE