Scott Peterson

I am going to start a new thread on this problem.
I am going to put more info in this tread for others. This is an 89 S4
Here is what I have done so far.
I replaced the crank sensor and the cam sensor, the ignition Control Units at the front of the engine bay and the temp sensor on the top of the intake.
I checked to make sure the fuel injectors were firing with a noid light and that was good. I can also smell fuel from the exhaust when cranking.
I have also jumped the relay for the ezk to make sure it's getting voltage. I also think this bypasses the alarm system.
Then I checked to make sure I had the crank and cam sensor getting signals to the ezk unit. I pulled off the connector and put an oscilloscope on the connectors pins that plugs into the ezk unit. Here are some pictures of the oscilloscope



This is the crank sensor signal.
Here is the cam sensor


So now I'm sure I have a good signal to the ezk. I have fuel pressure


But here is what I get on the plug wires for voltage

I don't think this is enough voltage to fire the engine
So what else will stop the engine from getting a good voltage on the plugs. The engine turns over fine and the car was running when i put it in the garage, but the next day it would not start.

GregBBRD

Is the cam belt still turning the cams and thus the ignition rotors?'

Mrmerlin

has the LH computer been rebuilt? how about the MAF?

Scott Peterson

We know the cams are turning or else we would not get the cam sensor signal. If they weren't turning the oscilloscope would be a flat line.
Yes the maf was rebuilt. Correct me if I'm wrong, but you can unplug the maf and the car will still start, Right?

Jason89s4

Yes the car will run poorly with MAF unplugged. Add an extra ground from body/fender to motor on each side to an existing bolt or screw nearest the injectors. 8 gauge or so.
I’m assuming that your well grounded everywhere else

ZEUS+

Have you checked kv on both coil wires ? With all the testing/cranking and fuel smell from exhaust, plugs could be fouled by now.

Mrmerlin

What was the last thing you fixed

Shirah

Double check your coil to distributor connections (the two short cables)

I also did not see where you tested the coils.

Mrmerlin

or answered the question about the LH being rebuilt

Scott Peterson

The EZK has not been rebuilt.
I'm going to see if I can find one to try out. I'm hoping Motorsports has one he will let me try/buy. I'll give Garity a call.
I don't think the LH could be the problem, the fuel injectors are firing fine.
I have also cleaned the engine ground strap and the rest of the grounds in the engine bay. Including the ground straps on the 2 coils.
One thing I am going to check tomorrow is making sure the EZK is getting power. I am going to check the relay is getting power then check to make sure it's getting to the EZK.
I did not check the coils. But both sides have about the same KV on the plug wires. (low/none) so I'm thinking it might be a signal issue or ??? I do have some spare coils I could install. But both going out at the same time would be a wild coincidence.
The last thing I worked on was the Hall sensor (camshaft) that's why I put an oscilloscope on it to make sure it was getting a signal to the EZK. As you can see in the pictures, it's working perfect.

ZEUS+

A test light to the neg coil terminal will flash during cranking if there is signal. There would be no secondary ignition kv (plug wire voltage) without signal.

Mrmerlin

Ok if your LH has not been rebuilt now is the time and or swap in your LH to a known good running machine The LH is the computer that usually fails and is the part that gets rebuilt

But an EZK could also go bad

Scott Peterson

I found a good LH and a EZK out of a 90. They are on their way to me. The 90 and the 89 used the same part on the LH and the EZK. So, I shouldn't have to do anything other than just swap them.
I'll let you know what happens.

davek9

Also unplug the the Two Ignition modules that trigger the coils, make sure the connections are clean, it's not common that both would fail at the same time though.
You should see a Signal on their harness coming from the EZK to trigger the coils

Dave K

Scott Peterson

Here is where I am.
I sent my LH and EZK to Roger. He tested both of them and he says they are working.
Now I am stuck. I thought I had tested everything needed to make the car run.
Do I now just go through every wire in the engine compartment and make sure it's good? Maybe the anti-theft system?
Just to review: The fuel system is working fine, I'm getting injector pulses to the injectors and crank signals to the computers. But it's just not making a good spark. I have cleaned all of the grounds in the engine compartment (again) and changed theIgnition Control Units