Cylinder 6 misfire woes

[Z3J1]

New-to-me Z3 came with P0306. It’s just a beater I’m trying to have fun with at minimal cost. Here’s what I’ve done to no avail:

1. Checked compression at 165-175 psi at all cylinders.

2. Swapped coils, plugs, and injectors to different cylinder and code did not follow.

3. Replaced original coils with aftermarket coils with good reviews.

4. Replaced original plugs with single prong copper.

5. Replaced CCV, intake gasket, throttle body gasket, and most vacuum lines. A couple original ones remain but appear good.

6. Battery unplugged to do a hard reset on ECU.

With every change, CEL is pretty consistently popping up cylinder 6 misfire but now and then another cylinder will show up.

The mechanic said the injectors are spraying sideways and PO said they cost $70 total so very low quality. But when I swap, the misfire remains at cylinder 6. Should I try refurbished OEM injectors from a highly rated ebay seller?

Smoke test? Check voltage at injector, coil, and plug? Any other common culprits I should look into?

 

[ExMX5owner]

Wiring, is what i would look at next..

 

[Z3J1]

Wiring, is what i would look at next..

Any guidance on what specifically to do? I’m just an electricity idiot with a cheap multimeter.

 

[ExMX5owner]

Any guidance on what specifically to do? I’m just an electricity idiot with a cheap multimeter.

You have pretty much eliminated anything that could be causing it as far as I see, aside from the only thing you can't really bypass or eliminate.

Any guidance on what specifically to do? I’m just an electricity idiot with a cheap multimeter.

No not really, the only reason I mention it is that I had a similar problem with one of my Mazda's, checked everything, swapped everything that could be swapped, and it turned out to be a dodgy plug. and worse still , it was intermittent in that it only happened when you were not trying to find it..

 

[t-tony]

I would get a can of electrical contact cleaner and dose every ignition and injector connector that you can find. Is P0306 the only code it shows and what does it say in words?

Tony.

 

[Z3J1]

Here’s more info that may be helpful.

I followed these directions https://www.youtube.com/watch?v=1Owjx2I1jZw which apparently resets the ECU. I cleared the code with my Bluedriver OBD reader. Car started a little rough but after warming up, ran fantastic for 12 miles without a CEL.

Then I parked it for about an hour and after starting it up again, the CEL came back with a cylinder 6 misfire and it was indeed not firing at all. Does that help?

 

[Andyboy]

It might have a faulty Number 6 coil driver in the ECU.

What year and what engine?

 

[Z3J1]

It might have a faulty Number 6 coil driver in the ECU.

What year and what engine?

2000 2.8 manual

Is there an easy and cheap way for a dummy like me to confirm that before sending the ECU out for repair?