For you MFI Gurus

[72T]

My 72 2.4 MFI was adjusted several months to a very rich setting by a mechanic, who runs one himself and says "these love lots of fuel". It is running well, but very hot. Like 250 degrees after 15 minutes hot. Metal popping sound hot. It used to run only around 220 unless under extreme conditions. The motor is a bit tired, for sure, and the mechanic said he wanted to be sure I don't lean out and burn a piston. He may have even said it is at full rich now. I'm trying to learn how to wrench this thing myself, but before I start twisting on a complex unit, I was wondering if the rich setting could be causing the heating problem. I know how far away from a Quadrajet this MFI pump is, so any tips on how to gently adjust the setting without making it worse?

[Jeff Higgins]

Rich running usually results in cooler running.

Boy, where to start... We need a bit more information from you before we know just where to begin.

From the temps you mention, I assume there is no front cooler. I'll also assume you live in kind of a warm place. At any rate, this is "too damn hot" (Bruce Anderson's words) under any conditions. Mine used to get that hot only on the track, and only on 90 degree plus days.

Something else is making it run that hot. Even your previously "normal" 220 is "track hot", like at the end of an extended session. You say it is "tired". What is "tired"? What is its general state of repair and tune? Engines tend to run hot when they are generally worn out or even just out of tune.

Anyway, before you start turning screws on the MFI, tell us more about your car and its motor. We will be able to help you much better with more information.

[356RS]

Are you sure the MFI was adjusted toward rich? Or maybe it was adjusted toward a lean condition by mistake? Was the distributor timing also played with at that time?

[Zeke]

Yeah, what does the tailpipe look like after a long run? Or plugs? Check both (plug when cool) after a run with very little low speed driving to the garage.

[Plays with cars]

Can you run it lean enough to make it hot under normal driving conditions w/o it starting to pop through the stacks? I think Mark is on to something with the timing.

[Eddyvdw]

From personal experience I would first check if all the hoses are right. Especially the one between the HE and the Thermostat (2 hoses, 1 under the car and 1 in the engine compartment). The thermostat will lean out the engine when warm, if it doesn't get hot (or work), the setting will stay rich. Also fuel smelly oil is an indicator.
Ed

[911st]

Also, might check your ignition timing and operation.

Hot temps usally come with late (retarded) timing as the fuel is still burning as it enters the exhaust.

The 2.4T seemed to have a flat spot off idle and setting them to rich was one way some try to deal with that. You can try to keep doing work arounds but at this point you will probably be much happer in the long run if you just send the pump in for recalbration.

A custom muffler can add to the problem in some cases.

[72T]

Thanks for the replies. Yes, there is for sure unburned fuel in the exhaust, as I can smell it (since he tuned it) coming off throttle at a traffic light, etc. I'm pretty sure about the full rich, given his "these love fuel" comments. I'll check the hoses. For more info, the car is a Central Florida car, but has been since 1980 without this issue. By tired I mean burns oil, the worst cylinder (by far) on the last leakdown was around 15%, but it runs strong, and pulls well through the RPM range. On the timing issue, I have been experiencing some real trouble with cold starts. Plenty of fuel odor back there, though. Changed the rotor, dist. cap and tried a spare coil, and it started, but wouldnt' this morning with original coil, so I'm thinking the spark might be weak, because it is sending one to the cap. Wouldn't start all winter, from the time it started getting cold until it finally warmed up this spring. (Yes, we actually had a "winter" this year) The car is bone stock, except for the recent Permadoom cdi that replaced the original. And the Bruce Anderson comment - "Excellence" subsriber here - is what got me to post this. One last thing, this car has historically gone through points like crazy. Thanks for the help.

[dicklague]

I would be sure the ignition is spot on. Check dwell and timing.

At some point I would put a Pertronix Ignitor in there rather than the points. This is a great modification and you won't have to worry about points any more. Our host sells them and the price is around $100.00. Updates the ignition to Hall effect electronic points. You just have to get switched 12vdc to the module.

[regency]

Well, I like to "steer clear" of mechanics that use "one liners" to comment on a problem. I once had a so called engine builder say to me, "just drive it, older 911's don't make oil pressure".

In your case, I think there's a lot to find out by a real mechanic.

Steve

[Jeff Higgins]

I agree whole-heartedly with dicklague - get a Pertronix Ignitor as soon as possible. It goes through points so darn fast because we simply cannot buy good points anymore, no matter the color of the box they come in. Even brand new points are suspect in my book these days. I have lots of older vehicles, bikes and cars, that originally ran them. They have all been replaced with some sort of electronic pickup or another. I suspect a lot of your "MFI problems" will be resolved with this change. At least it will provide a reliable, steady baseline from which to trouble shoot the MFI. You don't have that right now.

[Peter Zimmermann]

Please define "full rich." In other words, what is the measured CO% at idle, and at 2500 rpm with the engine at between 160-190F oil temp?