Adj. idle on 2.7 mfi engine

[bcgreen]

Will I need to stop the car each time I want to make an adj. to the idle mixture screw?

[75 911s]

Yes. If I understand you correctly, your problem is that idle is moving all over the place. Something else is wrong. You need an MFI guru to look at it. The RPM transducer relay compensates by reducing fuel when RPM is below 1300. Is everything plugged in? Is this a hot rod or stock MFI setup?

[john walker's workshop]

Yes.

[75 911s]

You could hire a little person to sit back there, but they might get really hot. And the fumes can make them angry.

[BURN-BROS]

lol

[bcgreen]

Originally Posted by 75 911s

Yes. If I understand you correctly, your problem is that idle is moving all over the place. Something else is wrong. You need an MFI guru to look at it. The RPM transducer relay compensates by reducing fuel when RPM is below 1300. Is everything plugged in? Is this a hot rod or stock MFI setup?

No, the idle is just a little low, it runs better if pull up just slightly on the handle throttle.
Total stock. I could just leave it alone but I just want to get it a bit better

[75 911s]

In that case I would just ever so slightly adjust the idle screws on the TBs. Then Drive it. I'm talking like less than a 1/4 turn at a time. Mark your start position or you will go down a rabbit hole of black art MFI tuning.

Drive it first to get it to temp, then do a slight adjustment to all 6 screws, drop the hand throttle to the floor and see where that puts you.

[bcgreen]

Originally Posted by 75 911s

In that case I would just ever so slightly adjust the idle screws on the TBs. Then Drive it. I'm talking like less than a 1/4 turn at a time. Mark your start position or you will go down a rabbit hole of black art MFI tuning.

Drive it first to get it to temp, then do a slight adjustment to all 6 screws, drop the hand throttle to the floor and see where that puts you.

Going to take pics.

[john walker's workshop]

Mixture is at the pump. Speed is the air screws on the stacks. They are adjustable with the engine running, the mixture adjust w/not running. Mixture adjustment can also change the idle speed. So, 6 of one, 1/2 dozen of the other.

[BURN-BROS]

These cars are old, I don’t think I would make any adjustments until I removed the mfi thermostat and ran an adjustable plate there to verify I am making adjustments on a fully “warmed” up injection pump. The thermostat thermal washers likely have wear and there is a decent chance the thermostat never goes to the full lean position. Also, all adjustments need to be done on an engine that is up to operating temp. Air flow should be between 4-5kg/hr at idle.

[tobluforu]

If your idle is low and that is all that is wrong, buy this: https://www.amazon.com/Latest-Rage-5385730856-Carburetor-Airflow/dp/B00CMC57R0/ref=asc_df_B00CMC57R0/?tag=hyprod-20&linkCode=df0&hvadid=309898128610&hvpos=&hvnetw=g&hvrand=17170621531131431622&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9021760&hvtargid=pla-568420224882&psc=1
Also get yourself a really long screwdriver, one that is 2 ft., give or take. Get your car nice and warm, pull over, pull air cleaner, stick the device above in each stack, find the one that is receiving the most air, adjust the others to match. If that isn't enough after you drive it more, then turn them out a little at a time. This might take a few times to get right.
Good luck.

[bcgreen]

I have one of these that I useto use on the webers on my TR6
https://www.amazon.com/Edelbrock-4025-CARB-SYNCHRONIZER/dp/B00062YC2E

[MikeDL]

I like the Uni-Syn for the SU carbs on my Healey, but I think the Weber redline works better on the MFI stacks.

https://www.amazon.com/Redline-Carburetor-Synchronizer-Synchrometer-STE-SK/dp/B08MWRDZJC

There's a slippery slope thing here...I have to admit I couldn't get them perfect until I pulled the throttle bodies off the car and synchronized them using the shop-vac technique here:

Another MFI correlation attempt. . . LONG

[bcgreen]

Originally Posted by MikeDL

I like the Uni-Syn for the SU carbs on my Healey, but I think the Weber redline works better on the MFI stacks.

https://www.amazon.com/Redline-Carburetor-Synchronizer-Synchrometer-STE-SK/dp/B08MWRDZJC

There's a slippery slope thing here...I have to admit I couldn't get them perfect until I pulled the throttle bodies off the car and synchronized them using the shop-vac technique here:

Another MFI correlation attempt. . . LONG

I don't want to get too carried away with this. It runs just fine as is so I will let the next owner deal with it.

[RSTarga]

Check your timing and make sure your distributor is free and retarding correctly. These run a retard at idle rpm. Check full advance at higher RPM with no vacuums hoses and then check at idle with hoses connected.

[bcgreen]

I did a tune up not long ago, everything spot on. Just need to fiddle with the idle sometime when I have nothing to do