MFI thermostat/mixture question...

[frank912]

Hi All,

Recently received my 69 targa with a 2.4T MFI engine. I have a problem with my mixture being too lean (popping under deceleration and hesitating (shaking like lack of fuel) under throttle. Did my valves, timing, plugs, points etc and the car runs great when cold, but ones it warms up it becomes too lean.

Disconnected my thermostat hose today and it took much longer for the hesitation too become apparent. I have cleaned and checked my thermostat (25 pairs and 3 washers) and now I am wondering what to do.

Question: when the thermostat warms up....does it lean out the mixture up to a certain point (I mean it there a 'stop') or does it lean out as far as the needle comes out of the thermostat? If so, I could for instance replace a few pairs with rings to minimize the length and therefore the lean out.

I could also make the general mixture richer, but then the car would be perhaps too rich when cold. My mechanic told me that it could be a bit richer as there are no small black smoke coming out of the exhaust when giving throttle. Not sure whether this makes sense?

I am aware that the MFI performs best on a rich mixture, but because the car runs great when cold, I am in doubt what to do:

- make the general mixture richer
or
- limit the amount of fuel squeeze by the thermostat??

Just wondering what would be wise. Intent to take the car for a spin without the thermostat internals to see how it performs.

Regards, frank

[edmayo]

ASSUMING !!!! everything else is okay (and probably not!) you could just richen the rack 2 clks. and see what happens. If it becomes acceptable then you're done,,,,,if not but it is better go two more clks. rich. If you're not where it runs right then stop,,,,that isn't your problem,,,4 total clks will be enough if there are no other problems. I suspect that you're going to find incorrect linkage adjustments,,,,usually what happens if engine has ever been apart.