LEAN Running

[nitroracer]

What are some of the reasons a SEFI car will run lean? I pulled one of my plugs today out of curiosity and they are white. The electrode is white and there is white residue on the metal where the threads are.

[88MercWagon]

dirty injectors, screwy sensor somewhere? Maybe the SD sensor is out of whack, and it's underestimating the amount of air coming in. Makes some sense, doesn't it?

[mrltd]

Fuel pump, fuel press reg, bad fuel filter, vacuum leak...

SD sensor? what's that?

Could be TPS or 02 sensors too, I guess

[JeffBoudah]

if your FPR was bad it would run rich, a vac leak would also cause it to run rich. a bad MAP sensor (im guessing that would be the SD sensor mentioned earlier) would cause the car to run bad all around. an worn out fuel pump might cause it if it cant supply the required pressure. also a cloged filter could drop pressure. are your plugs white or more of an ash color? the only way to get a true read from your plugs is to do a WOT run, shut the car off and pull a plug. and get a fuel pressure gage, they are about $25 and go right on the shraider valve on your fuel rail (under that little black cap on the rail).

[mrltd]

Really? my FPR was bad...mine ran lean as hell...if the FPR has no vacuum it;ll run rich....

[JeffBoudah]

I had one go out on me also and it ran my car rich. i would pull the vac line off and have gas coming out the nipple. guess there is more than one way they can die...

[nitroracer]

The fuel pump was replaced about 6 months ago with a 110lph mustang pump. new filter about a year and a half ago. The regulator is an adjustable piece and was set at 40psi, I bumped it to 50psi a few minutes ago. It is functioning right because the pressure changes when I pulled the vacume line. I even checked the vacume because I found the gauge in the garage and I was pulling a solid 19lbs at idle. I have a spare TPS in the basement and I believe the 02s are good. Im going to go check the codes on it now.

[mrltd]

What setup are you running Matt? The 19s or the 14's? Ho cam?

[nitroracer]

Full HO, 19lbs, HO cam, everything.

Just ran through the codes and I may have solved one of my cars problems. I got a 42 and a 92 which say the right side oxygen sensor is always reading rich. Might fix my other problem too of breaking up in the high rpms.

[mrltd]

That'll do it...make sure the wiring isn't hitting the exhaust..Get mustang application from the same year...they have longer harnesses.

[nitroracer]

I extended the wires on some stock ones last time and they've been good till now. Im going to mess with the plug on it tomorrow and make sure I haven't melted anything.

Gonna give this a try too: http://www.shotimes.com/php-bin/modu...thold=0&sid=87

[85crownHPP]

Definitly verify the fuel pressure if you havent already. Maybe even check the injector wiring with a noid light to make sure they're all firing.

auto zone sells an air fuel gauge like mine for $25, you can get them new on ebay too. You have to figure out which wire to tap into on yours, if no one here knows Im sure one of the mustang guys can tell you.
Ive always thought it wouldnt be neat to hook up both sensors and use a SPDT switch to toggle between the two sides!!!!!!!

[mrltd]

Those gauges are worthless....nice only for a lightshow. Real wideband is needed. Those are a bit more expensive.

[85crownHPP]

they arent worthless, they will tell you if you are running way lean or not. that alone is worth the 25 bucks!!!!
But you are right, they arent accurate enough for tuning purposes.

Mine reads ideal during criusing, rich when acellerting more than grandma, and lean when your off the throttle and the vacuum spikes.
Worthless!!!! bah!!

[mrltd]

you just like it because it's a bunch flashing LEDs!