mc2100 trouble

[Collin the Hen]

Hey, guys
I've still been having trouble with my MC2100 in my 258. I've got it to idle reasonably low, but it still wants to diesel. Does anybody know what size jets are ideal for the 258? Mine are 48. My A/F screw is 2 1/2 turns out and my idle screw is all the way out. I'm guessing it's idling at 850 to 900. My timing at curb idle is at 6 degrees with vac disconnected and plugged.
ANY advise is very helpful!

Also, have any of you with the mc2100 swap changed your timing at all?

 

[lah2420]

I think I am running 46s in mine. It was running way to rich with the 49s that were in it. They may be 47s, but I don't think so. The jets actually aren't used during idle though, except to allow the fuel into the idle circuit. Your mixture screws control the amount of fuel for idle. If the throttle plates aren't closing as far as possible, such as the linkage holding it open, you may be getting too much gas. That could cause the dieseling. It's probably something to do with that or possibly a vacuum leak. Mine had the same problem that turned out being that the previous owner decided the EGR valve didn't need a gasket.

My timing is set at about 9 or 10 degrees. It seemed to run better that way. For reference, mine is nuttered and using the TFI ignition.

I used this site to get a lot of info on the 2100 too.
Motorcraft 2150 2V Carburetor

 

[Collin the Hen]

Thanks a lot! There is a vacuum leak, I think, at about 1200 rpms or so, but I can't find it for the life of me. It sounds like an old TV. It has a manual choke, so the other day I filled in the auto choke hole at the bottom of the base plate.
Also, the previous owner disconnected the EGR, so I don't know if that should be hooked up or not.
Thanks again.

 

[lah2420]

I accidentally lost my EGR valve. The previous owner had disconnected it anyway. There's a plate over that hole now. It is possible for the leak to be your EGR. It is basically a vacuum operated diaphram that opens up a port and allows some exhaust gas into the intake after the carb. It may be stuck open. It's supposed to close at idle.

 

[Collin the Hen]

How did you make that plate? Is there anything I need to do before I take it off? Did you buy a gasket, or did you just use RTV? Thanks a lot for the input. I tried to see if it moved at all after I drove it... didn't budge.

 

[lah2420]

A friend with a torch cut it out of some 3/16 inch plate he had. He just took off the EGR and traced it out. He also had an extra gasket that I used.

Are you sure the base of the carb is sealing off? I've heard that the screws on the power valve cover interfere with some brands of the adapter plates. I didn't have that problem though.

 

[Collin the Hen]

I made my plate yesterday. It looks a lot nicer than the EGR, but there's still a leak, so I'm going to take off the carb for the fifth time and use gasket sealant on everything. The plate was ground down where those screws are, but thanks anyways! Hopefully it'll be the last time I'll take that carb off in a long time! :x

 

[lah2420]

One other thought. Are any of your intake manifold bolts loose? I'm just trying to think of all the things I've dealt with since I bought my jeep. They aren't torqued real tight, so don't just crank them down. I don't remember the specs. That kind of leak may not affect it the way yours is doing though.

 

[Collin the Hen]

Thanks again. I'll try that. I'm still waiting for the sealant to dry, so tomorrow I'll give it a wirl :deadhorse: