MFI question

[jkeyzer]

I pulled the plugs tonight and some cylinders are running much richer than the others despite the correlation being pretty good at idle (I assume it is not above idle). After 300-400 or so miles on these plugs some are white with black smudges and a couple are very black all around (rich, maybe bordering on becoming fouled). What's the best way to fix this?

Should I put all the idle screws at the same spot and adjust the throttle plates themselves to try and even things out (at idle)? Or should I bring the engine up to 3000 rpm and adjust the idle screws or throttle plates to get them the same at that point?

The linkages are adjusted pretty well, and one of the fouled plugs is #5 which should be less susceptable to linkage misadjustment, right?

Also how long does it usually take for a spark plug to show whether you are running too lean or not? Are the white plugs after 400 miles telling me those cylinders are too lean?

[Paul Thomas]

Jeff,
Are you absolutely sure that your pump is timed right? What you're experiencing sounds like a problem i had last year, i thought that the timing was right but wasn't, and although the car ran pretty good I had some plugs that consistently looked good and some that looked like they were fouled.

Also, have you done the intake correlation with the linkages off and then adjusted them to fit? Until i had my throttle bodies rebuilt my air screws did little or nothing.

Paul

[jkeyzer]

Paul -

You know, I checked the timing tonight, and it is a little off. How perfect are we talking? This is within a few degrees. I tried to loosen the pulley but the allen bolts are in very tight. I'd probably have to remove the pump again to get them loose.

I haven't done the idle correlation with the linkages off actually. I was hoping that any errors I made there would be small enough not to worry about for now. I also haven't changed the throttle plate position at all since I set up the stacks initially on the bench, all 1 turn in past where they get stuck shut. So there are probably errors there. It was just weird to see one plug bright white and an adjacent one black and sooty.

#1 - somewhat sooty
#2 - slightly sooty
#3 - very sooty
#4 - mostly white
#5 - very sooty
#6 - mostly white

[Paul Thomas]

Jeff,
Don't you sleep? What is it 4am there? Before i had my throttle bodies rebuilt i had all of the problems you descibe and now they are perfect. I know i sound like a broken record but this was one of the few things, not high performance related, that i have seen i big difference.

Cheers,
Paul

[jkeyzer]

Paul -

I live the life of a graduate student at UCSD... My sleep habits are pretty random sometimes as there is noone to tell me to get to work by 8 and there are still people in my lab at 2 and 3AM sometimes!

The benefit I can see getting from a rebuild would be having the TBs set up on a flow bench. I think wear-wise they are ok, especially because I am seeing different plugs fouling now than before I removed them and re-did the throttle plates.

Of course this all still doesn't explain why my idle won't stay at a constant rpm.