MFI blues

72 four door · 11-25-2003, 04:25 PM

My T starts a little rough which i know is normal from what i hear but after its warmed up at low rpm it stumbles.pops out of the stacks once it gets above 3 thousand rpm shes great. So what does that mean ???

HawgRyder · HawgRyder's Garage

My first guess would be air leaks.
Gaskets at the base of the stacks (2).
Perhaps the throttle plates are too worn.
With MFI (and every other form of induction) perfect fit of parts is necessary for great running.
Everything that is worn will contribute to the engine being "not quite right".
Bob

pwd72s · 11-25-2003, 05:06 PM

Air leaks or perhaps timing a bit off? Assuming, of course, all's okay with the engine hard parts...just guessing...

72 four door · 11-25-2003, 05:14 PM

Ichecked the throttle plates and they were seating well before i installed them i couldnt see daylite thru them wjich tells me they were good. It has new gaskets. again once at speed shes great.

jeff m · 11-25-2003, 08:19 PM

Cleaning the dist is a quick easy job that could help.
Also check vacuum from 1 & 4 to the dist.
Jeff

P.S. Assume the two thermostat hoses are both on.

jluetjen · jluetjen's Garage

Quote:

again once at speed shes great.

Keep in mind that once "at speed" the amount of air being drawn through the throttles is a couple orders of magnitude larger (100x? 1000x?) then the amount of air being drawn when at idle. So any air leaks which are a big deal at idle fade to the far reaches of insignificance at part or wide open throttle.

I'd follow the process outlined in the MFI troubleshooting documentation ("Check - Measure - Adjust". First I'd confirm that the engine is mechanically in good tune and that the ignition is timed correctly. Then I'd start poking around looking for air leaks with all of the usual suspects, gasket surfaces, throttle shafts, etc.