David Dale

Alright so one day after working on my car i started it up to find that it was running crappy. After checking my timing to see what was going on i found that the trailing 2 wire was not sparking, however the trailing 1 side was functioning fine. I checked my resistance of my coil and it was fine, i then swapped out my trailing coil with another one that i had. Same thing. Also i was not getting the correct voltage to the coil

im not too ignition system savvy so i could use some help

I was curious if a bad spark plug would cause the timing light to not flash if i had it on the spark plug wire.

also i was looking at a wiring schematic, checking out the wires going to the ecu. there was a timing signal, a select signal, and a confirmation signal on a 4 wire connector, and then there was a two wire connector that seems to be connected to the power side of the coils.

so...what would cause only one coil to fire?

satch

iTrader: (1)

When you said that you had a problem getting the correct voltage to the coil what did you mean ?

Also, check the wire for the coil which relates to the "select signal." Not sure which wire this is on an S5 but if you look in the Fuel and Emission section of the FSM it will provide you with the color of the wire and its position at the ECU. This select signal wire tells the coil which plug to fire (as in T1 or T2) so this might be your problem. You also might want to switch trailing sparkplug wires to see if the problem is caused by a faulty wire or not.

bumpstart

if the toggle select is not working then you are wastesparking the trailing plug that is functional

bad news

get onto it quick,, be sure that you see 1 V every other revolution of the engine at the toggle wire

David Dale

I took the little plastic cover off of the trailing coil that says T2 and seen 2 little nuts where 2 wires go to. one side has a plus sign, so i put the positive lead of my multimeter on the positive side next to the little nut on the little tab and the negative lead on the other. I had the ignition on but the car wasn't idling and it was only showing like 2 volts or something and i figured it wasn't correct. Tomorrow morning im going to retest all the wires going to the coil and i'll write down all the measurements so everyone can take a look.

ok i have another set of wires so i'll see what happens when i swap them out

I have a wiring diagram bookmarked and i've been kinda looking at it

David Dale

alright i went and wrote down everything i got...

this was done with the ignition on

first off i found that when i was checking voltage on my coils if i put my neg lead on the neg battery post instead of the negative side on the coil it would pop up with 11.86 volts and would be 0v when i put it on the neg side of the coil (this happened even on the functioning coil so i figured that voltage getting to the coil probably isn't a problem after all...

At the 4 wire connector i took 4 voltage readings while the ignition was on with a positive lead going to the connector and the negative going to the neg battery post:

the fsm voltages for the wires at the ecu are in brackets

1. The blue wire with a yellow line (timing) 4.98v [0v with ignition on .8v at idle]
2.the brown wire with a yellow line (select) 4.99v [4.4v ignition on 2.2 at idle]
3. blue wire with a green line (confirm signal) 4.99v [below 2v ignition on 4v at idle]

the 4th one goes to the instrument cluster

so there seems to be a problem with the timing signal since it is supposed to be 0v not 5v. And the confirmation signal is more than twice as high. What causes higher voltage to happen like this???

bumpstart

colours ( at the coil ) i have are tan = 12v,, red = signal,, white= toggle select, other is tacho

the red is 5V square wave,, falling trigger

the tan wire goes back to a connector and should be black with yellow from there

the white one should go high ( 5V ) for the T1
[ 5v? i think maybe some aftermarkets can toggle ok with a 1V? ]

and zero ( low ) for T2
( test by maybe disconnecting the toggle wire and see if t2 sparks )


it is normal for both + and - pins on the coil to show 12v when hooked to earth across the DMM
and show zero when measured across the same pins

David Dale

well i checked the voltages for all the wirins going to the trailing coil from the ecu, and they are in spec...but somehow the voltage is still 5v when i check it at the trailing coil connecter...is this normal or is there a posibility of two wires crossing and some point and causing a problem?

Turbonut

iTrader: (1)

Rather than using a timing light to test, remove a trailing coil wire from the plug and see if there is a spark to ground.

HAILERS2

The timing signal rises and falls from 5 vdc to 0 vdc AS THE ECCENTRIC SHAFT IS TURNED.

So it would be normal to see 5vdc on the Brown/Yellow wire if the crank isn't being turned and it might be normal to see zero or close to zero on the brown/yellow if the crank isn't being turned. So monitor the brown/yellow while turning the crank/front pulley with your hand. Matters not if the crank is turned cw or ccw.

IF one of the trail coils is firing..............then it's a given that the timing signal is going from zero to five and back to zero and on and on and on like that.

Start the engine. With your hand pull the trail sparkplug wire out of the coil just a touch. See if you see spark or not. Keep your body off the chassis and you won't be shocked.

Sure you have the trail plug wires on the right plugs? Not one on two and two on one?

A traill coil assy laying in the backyard won't cause the engine to run funny at idle or lower rpms. You won't even know its not there other than the tach not working.

It's the ignitor inside the trail coil assy that actually causes the firing of the coils ...........by seeing the rise and fall of the signal to it from the ECU.