working through some issues on the s4
have tried two different trailing coilpacks

was trying to set and check timing, hooked timing light to trailing no spark.
with plug wire off and engine running, spark every once in a while.

have checked and redone the ground by the trailing
got nothin

tach works, car runs alright under light throttle trailing never kicks on

where should i start past checking grounds

 

tested trail coil harness
results while running
blue red wire- 1.3 v
brown yellow- 2.2v
blue yellow- .79v

neither coil t1/t2 firing according to timing light, good grounds. tach does work, which i thought it shouldnt when trailing is bad

s4 na 86

i DO NOT get the 0- 5v switch when turning motor by hand on the brown yellow wire

 

What grounds are you referring to? The only ground is the contact point between the coil bracket and the fender. Your voltage readings on the three wires is up to spec.

Try testing for spark by pulling the plug wires from the coil bores and placing the plugs very close to the bore but leave a fraction of an inch between the bore and plug and w/key to start you ought to see some sparking. If you see spark then your problem could be the plug wires and or plugs. Also, if the electrical system voltage drops too low it can cut the trailing coil.

And unless you have the bullet connectors of the two coils jumpered then the only thing that drives the tach is the trailing coil.

 

Voltage gauge on dash is a lil sticky, only shows 12 volts when running, I will test with multimeter, I read about voltage drop dropping trailing coil. If it drops it will tach still work? Performance wise would this be a cause of rough starts and high rpm and throttle position stuttering?( have good tps and new injectors a day away, covering bases) have read trailing are deleted on some cars, if they make the engine run smoother I want them of course. Spark jumps hard and hurts haha, not as fast as timing light blinks but it does make a strong jolt a second.

New plugs 7s and 9s
Wires are newish
Wiring has been highly tampered with not sure if jumper wire or not

I believe grounds to be good, I've redone every single one in engine bay. And blue/red wire voltage indicates a good ground

 

The bullet connectors at each coil are less than 5 inches long and are not connected to anything. If they are jumpered to each other then it should be easy to discern.

And what about the grounding?

If the trailing coil doesn't work then the tach should not work as well.

 

Also read a simple inductive timing light might have trouble picking up trailing coil? Grounds are good just forget those I'm that confident that the engine is more than sufficiently grounded including essential sensors. Tachs working so it has to be working?

 

Yes. I've had this problem also with an inductive light, the type that clamps around the plug wire.

 

Alright ill ignore it for now, do Injectors and tps and see if it smooths out