1994 fd3s
single turbo
all fuel upgrade
fmi
no a/c no p/s
new wires new plugs

ok so my car was fine and all of the sudden it started to ild rough and my a/f was lean at around 17.1:1 at idle.... all the fuel is ok.

so i was checking the plug wires and i pulled the top leading plug half way off the coil to see if it had spark and the car idled perfecr.... so i put the wre all the way back in the coil and it idle like crap...

so it will only idle good *normal* when the top wire from the leading coil is half way off...... anyone ever seen this?? im thinking about replacing that coil but want to make sure its bad before spending 120.00 on it.


any advice will be great.... also the coil bracket has good grounds i even aded one new on..

 

no one?

 

Did you somehow flip your leading and trailing plug wires when you changed them?

 

no i chaged them 1 month ago and it was fine ever since.

it only idles normal when the spark jumps an air gap from the coil to the wire when its barely on

 

Have you pulled the plugs and cranked the car to see if they are all sparking?

 

Pulling the wire off is acting as a booster gap. 1) I'd check or change the plugs, again; and, 2) take a closer look at the plug wires & connections if necessary. Your problem is not likely the coil--I'd put my money on a bad plug. Note that plugs and wires can look great and still malfunction. For that reason, you're best to sub them out with know good units, even if used. Been there, done that.

 

i did and they are all sparking.

 

as was said could be a shorted/cracked ceramic plug, or a shorted wire assuming that they are not crossed with the trailing somehow

 

hey you were right. i changed my leading spark plug on the front rotor and the car is fine idles normal, thank you for you help

 

Is that with or without the air pump? You need to disconnect the air pump to get a meaningful reading (though your idle may get even worse then). I presume that number is from a wideband.

[Ooops - too late. Looks like you fixed it.]

 

i dont have air pump but changing my spark plugs fixed the problem....

 

On the subject of booster-gap, there used to be plugs made with the booster gap (0.030" or so) internal to the plugs. The booster gap's purpose is to make the spark voltage build-up much more sudden, since the current has to jump the booster gap first, so that the plug will spark before fouling could bleed off the voltage. Booster-gap plugs were fairly common in the old days of poor oil control, lousy carburetors, and the resulting rapidly fouled plugs.