mfi problem

[cmcfaul]

2.4 911 E.

When the heater hose to the MFI is connected car runs way lean at idle and partial throttle. Easy enough to fix, just disconnect the hose but it bothers me it's not working the way it's supposed to. Anyone else had a problem where the MFI thermostat corrects too much....way to lean when at normal operating temps? AFR meter will read 16+ and stall due to fuel starvation.

With the heater hose to the MFI disconnected it runs close to perfect. I can likely get it really close to perfect under these conditions but in the winter I will likely have issues as the thermostat is there for a purpose.

Should I adjust the mixture to run right with the hose connected. Will likely be really rich until warm.

suggestions appreciated.

Chris
73 911 E

[Adams911]

The adjustment needs to be done when the car is up to temp and the hose is connected and then give the speed pump 2 clicks and see how it drives. If it is still lean try another 2 clicks but the first 2 clicks might just do it. My new great old school wrench says to put the car in 5th at 20mph and floor it and it should go to red line and pull evenly all the way.


I had to learn to adjust my years ago because nobody here new what they were doing.

You need to find and follow the CMA if you haven't already…

Steve
1973T

[tobluforu]

Was it running fine before a/f wise, if so maybe the thermostat is sticking???

[dicklague]

I never did like that warm up regulator. I installed a button on the dash that manually actuates the cold start system and squirt raw fuel in to the throttle bodies.

I then removed the warm up regulator and made a cover plate and a 6MM X 1mm lever to push the lever in. this gives me adjustability for mixture that is a manual version of what the disks do, but I can use it for overall AFR adjustment.

I would not do this mod unless I had a good AFR instrument. I have a Daytona-Sensors Wego IV

[dicklague]

This is what the AFR setup looks like. the clock plug holds the Daytona-Sensors WEGO IV. I need to clean this up a bit as I just finished the new instrument installation. this is a first prototype.

The upper readout is a clock, voltmeter, thermometer combination. The right mini toggle is spring loaded pushing down and it toggles between the readings. If you hold it down for 5 seconds it goes into auto mode and scrolls through the instruments displaying each function for 5 seconds.

to set time, you push the switch up.

the left switch is for temp. I have 2 sensors, one for outside air temp and the other for oil cooler temp. The switch is to select sensors.

The CL on the AFR gauge is just telling us the sensor is cold. In this case the AFR is on, but the engine is not started.

[scotricker]

oh wait... I thought the headline said milf problem... nevermind... carry on

[cmcfaul]

I have a perminitly installed AFR and am versed on adjusting the MFI.

When I connect the hose and it goes lean, should I adjust the idle mixture first or the main mixture first?

I had just gotten it dialed in where I wanted it when I noticed the hot air hose was not connected on the bottom...ugg

Thanks,

Chris

[dicklague]

Originally Posted by cmcfaul

I have a perminitly installed AFR and am versed on adjusting the MFI.

When I connect the hose and it goes lean, should I adjust the idle mixture first or the main mixture first?

I had just gotten it dialed in where I wanted it when I noticed the hot air hose was not connected on the bottom...ugg

Thanks,

Chris

Sorry I missed the AFR mention. That is the sway to go obviously.

If you are that lean when the hose is connected you obviously have to richen it up. do you have notes of what you did on the last adjustment? I would go back to there and adjust the idle mixture first.

I don't mean to muddy the waters, but I took my warm up stack off a long time ago and went manual. I had the pump redone years ago and it was set to factory settings. Took the car on a New Years day run and it just ran worse and worse as it warmed up and finally would hardly run at all. I did some adjusting and got it back in tune, and then went on my AFR and manual setting the warm up system journey.

[tobluforu]

Like stated, two clicks richer on the top end and take it for a cruise and map it. Adjust more if need be, when you have it right, adjust idle mixture. Done.

[cmcfaul]

OK will start with the main mixture screw. I did keep track of what I did while chasing a slight off idle lean condition. However, it's hard to fully know when the main screw is engaged and clicking. The idle screw is easy.

Will drive around with the MFI tools for a while until I get it right. Hopefully when properly set up for full opperating temps, it's not too rich when cold as most of the driving I do the engine is not at full temp for long (usually less than a 30 minute trip).


Chris

[tobluforu]

Try grinding down the edges of the driver that you are using to adjust the main, this will help with lining it up. Usually takes me about 15 seconds or so of slowly turning the driver and moving it before I feel it drop into place.

[cmcfaul]

I have the actual Porsche tools. It's a feel that I am starting to acquire. Getting better at it and know I am under the screw when I miss it.

Chris

[356RS]

This might be a good time to check the Baro Cell. When the bellows in the cell start to crack and then leak, the bellows expand and then moves the balance bar in the regulator towards a much leaner mixture. Like it should @ high altitudes.

[tobluforu]

Originally Posted by 356RS

This might be a good time to check the Baro Cell. When the bellows in the cell start to crack and then leak, the bellows expand and then moves the balance bar in the regulator towards a much leaner mixture. Like it should @ high altitudes.

I read way back that one can shim these, is this correct, if so does it richen it up or lean it out?

[356RS]

Shims under the Baro Cell are part of the system setup during a rebuild. Adding shims will richen the mixture and removing shims will lean it. Shim size's are from .10mm to .50mm along with the standard 2mm spacer.