Help Reading Plugs

[Ocalafox]

Hey Guys,

I replaced the Autolite 25's yesterday (with same) after 10,000 miles. Plug insulators are bright white, electrode is very clean and flat (not rounded), full circle, but the back side of the ground strap (away from the electrode ) is also white. Using the plug guide in Turner's 79-95 5.0 book would lead me to believe it's running lean or too advanced timing.

Motor is stock short block w/171,000 miles, thumper heads, tmoss lower, 1.7 rollers, stock 19 injectors, 76 C&L with K/N flat panel in stock air box with the f.p. set at 40 with vacum removed. Timing is at 14 with spout out. If it is lean, what should I bump F.P. to? Engine temp. is usually 190 but did go to 200 this week in 95 degree stopped (hurricane) traffic with A/C on.

Car runs great, just don't want to detinate (sp) it.

Thanks, I'll check back until our power goes off (Frances).

vann

 

[LASTFOX]

The problem may be you Aftermarket MAF. Ford calibrates the OE MAF's to work wit the Stock computer. When you install and Aftermarket MAF and don't have you car tuned, it will have issues with running either to lean or rich at different rpms and loads. The aftermarket MAF's fake you OE computer out with a different voltage. Your computer reads this voltage (which is across the board change/flat out) and doesn't take into account different loads that the engine receives. Why don't you try putting the OE MAF back in, put the timing at 10*, and set you FP to 34-37 with vac on and see how your plugs look after a few hundred miles. Just my .02

 

[Ocalafox]

I agree lastfox it could be related to the increased air flow. But, how many bazillion fox's are running around with aftermarket maf's and no recal/chip used. Is there a way to richen mine up? Increase F.P.?

thanks,
vj

 

[Rick 91GT]

When are you reading the plugs? You need to read them right after a WOT blast, so go WOT then turn the car off drift over, get out pull the plug and read it.

Idle time will totally changed the reading on the plug.

 

[LASTFOX]

Ocala...If you adjust your F/P too high at idle then the car will run like dog. I'll give you an instance. Stk F/P for a 5.0 at idle is 34psi w/vac on. I adj.'ed mine to 40 @ idle at it ran like crap, esp. at red lights, wanted to stall. I took the press. down to 36-36.5 and it runs great. My motor realistically runs "Stk" until I put it to the board and then my FMU takes over and restricts fuel back to the tank, thus increasing my pressure to 60-65 psi. My point is that, if you increase you're F/P at idle, by a few pounds, it will move your WOT psi up, by a few pounds. However at the expense of low speed drivability. The best way to remedy your situation would be a tune! Hope you fair the hurricane OK

 

[Rick 91GT]

You can set the fp to 70 at idle, the computer will adjust the pulse width of the injectors to make the air fuel ratio "stoich".

When you add any fuel through the FP regulator the only place you get more fuel is at WOT.

Stock FP is 36-38 VAC OFF.