Vic995

I was 50 miles away from home, when my engine went rough (dropped cylinder). First thought was "Oh **** it's either the Coil Pack or the Ignition Amp".

After a moment of panic - about being stranded - passed I parked and raised the hood. Removed the plastic engine and airbox covers, started the engine and proceeded to unplug the Fuel Injector Plug for cylinder #2, looking for increased engine roughness and a drop in RPM. Engine RPM stayed the same.

At this point I was thankful to all those, before me, that posted in AudiWorld. I had a heads-up on what to expect and where to look. I remembered reading here in AudiWorld that a #2 cylinder misfire is a classic symptom of a bad Ignition Amp.

So to make a long story short, I simply left the #2 cylinder Fuel Injector Connector off so that the Cat Converter would not fry. Bosch may have programmed the ECU to shut-down the Fuel Injector for a continuously misfiring cylinder, but I was taking no chances.

I drove the car 50 miles home on 3 cylinders at 75 to 80 mph (3k rpm is the sweet spot for engine smoothness, when running only 3 cyls). Also interesting, is that I could drive 80mph and still have 2 or 3 inches of Mercury in the intake manifold (I have a vac/boost gauge) on only 3 cylinders.

Got home and swapped Coil Packs #1 and #2, then reconnected the #2 fuel injector connector. Started the engine, then unplugged #2 injector connector again, RPM stayed the same, pointing a defective Ign Amp and NOT a bad Coil Pack.

Best Online price was around $105, but I opted to pay $171 at Stevens Creek Audi and have the part right now (this was for the 8D0-905-351 part number Ign Amp).
My 99.5 1.8T had the 4D0 prefixed part number, but the 8D0 worked fine and was made by Hitachi in Japan which is important, as you will see later.

I popped the cover off the Ign Amp to do a failure analysis and try to understand why the #2 output is usually the only failure.
What I found was a manufacturing setup problem with the Wire Bonder on the #2 output tab. The pressure of the Wire Bonder was set so high as to almost completely "pinch" through that wire.

At the end of the day, it looks like Bosch had a Wire Bonder setup problem for a large batch of Ign Amps. My Ign Amp was one of those in that batch.

One thing for sure, the 8D0 part will not have the above problem as it is made by different vendor using different equipment.

Below are two photos of what I found inside the Ign Amp.

Here is what the Ign Amp looks like inside.
<img src="http://pictureposter.audiworld.com/2978/pos-inside2.jpg">

Here is a photo of the #2 Output Tab showing the broken wire bond (I actually moved it further for the photo). An Ohm meter pointed to the #2 output.
<img src="http://pictureposter.audiworld.com/2978/pos-output-2a.jpg">


Vic (1999.5, 1.8T, Tip, APR Stage I at 10Kmi, currently at 100Kmi.)

quattro nole (Jeff)

So...is that repairable?

ModifiedA4

nice pics!

Vic995

a bonder, it would definitely be repairable.

Vic995

thanks

GTRAFF

I took the cover off my daughter's ICM - misfire on cylinder #2 - and was able to solder the connector back on. I am not sure I actually had a good joint as it took a lot of heat and never looked like a good joint. Maybe it was just the flux holding it but it worked for a few days until I got a new HUCO one. Keeping the old one for a spare.

Audiboy

wires are bonded ultrasonically. I gave up after many attempts with high heat and different solder compounds.

I don't know how folks actually repair this. Must be a different soldering compound they used, or they are making a temporary connection which will pop out again in a short time.

ModifiedA4

perhaps they use a silver filled epoxy, if solder doesnt work, an electrical epoxy probably would.