MFI Idle Fluctuates

arrivederci · 07-02-2003, 06:28 AM

The idle on my '72T isn't consistent. It really is all over the place. In some instances, it won't even idle with the hand throttle fully down. Sometimes it seems like it sticks at 2000 rpm or so, but if I blip the throttle, it'll settle down to 1000 rpm. And sometimes it'll purr along at a low 500 rpm.

I'm guessing that something is sticking...but don't know where to look first. Ideas?

BTW, the flapper on the airbox has been removed. Otherwise, the complete MFI system is on the car.

304065 · 07-02-2003, 06:33 AM

Stuck thermostat. See archives for R&R instructions, clean the discs, you should be OK.

1fastredsc · 07-02-2003, 06:35 AM

Don't know much about the mfi, except fuel is controlled by that space cam in the distributor. Maybe timing?

arrivederci · 07-02-2003, 07:21 AM

Thanks...I'll take care of the thermostat.

warment · 07-02-2003, 07:28 AM

Sounds like the "microswitch" that sits underneath your throttle linkage in the engine compartment isn't adjusted properly.

If I remember correctly, the throttle linkage arm is supposed to depress this switch when you let off of the gas pedal.

Also, is the flapper box(WUR) arm preventing the throttle bodies from closing fully? The "wheel" that sits on the end of the WUR arm on my car was making my throttle stick, which prevented the car from idling in it's proper range.

Open the engine compartment and work the linkage with your hand to see if it is sticking...

Bill

warment · 07-02-2003, 07:29 AM

Whoops...I didn't see that your flapper box had been removed...Ignore my flapper box comments...

Bill

Tim Walsh · Tim Walsh's Garage

The other possiblity for flucuating idle is seal between the throttle bodies and cylinder head and the seal between the stacks and throttle bodies. I belive worn throttle bodies will also exibit this problem. Check for all of those

michel richard · 07-02-2003, 08:15 AM

Sticking advance weights in the distributor ?

Paul Thomas · 07-02-2003, 02:46 PM

Initially, i would not look at the MFI at all. First thing, i would check and see if my throttle linkage, from pedal to bellcrank on tranny, were not getting hung up somewhere. Next check to see if the throttle body lickage itself were lubed, working properly and not getting hung up.

If the throttle shafts were worn you would be getting popping out of the stacks and if you were getting air in under or around the throttle bodies the idle would just go up all of the time and you would get some backfiring through the exhaust.

Paul