My 88 s4 T2 when first started the tach works then quits as does the trailing coils.
I have changed out the coils and plug wires and plugs.
Also checked the wires to the coils.
Could it be the ECU is bad

 

Does the engine still run???????with the tach not working?

 

hmmm.

Do I have this straight? You start the car, it runs well, the trailing coil fires, and the tach works.........then the car runs, the trailing doesn't fire, and the tach dies? If so, is there any consistency? ie. after 30 seconds? or after I rev it past 3000?

Have you checked the harness for the trailing coil out for any bad connections?

 

the car still runs and yes it works for about 5 secon

 

I checked all the wires but still nothing.
the tach was working for a while until the revs dropped, then fell to 0.

 

well in my 88t2 i found out that when ever i did the egi fuse unflood meathod my tach would work for like 5 sec then die. you might want to check near the engine fuses, just a thought

 

I will give it a try thanks i thought mu ECU may be bad

 

it could be but i am just telling you what was happing to me when i pulled me egi fuse.

 

I will try to check out that and I'm going to trace some more wires.
I wanted to drive it in the parade today..

 

checked out the coil wires they are getting 12 volts ,checked the starter wires, and fuses
still no luck.
any thing else guys.

 

K, this may be a long shot but I had the same problem for months and couldn't figure it out untill one day I noticed I had some loose bolts that hold the trailing coil pack to the body. I tightened the bolt and I haven't had the problem since. All I can think is that the either the bolts holding it down act as a ground for the pack or it rattling around affected it. I know it sounds wierd and like I said it's a long shot but I swear that is just what happened to me.

 

I will recheck this but I added grounds on both coils from the mounts to the frame and battery. and reground the whole car with 8 guage and 4 gauge wires .
but i will check again. My son has been driving it some and u know how that goes with a 16
year old..