Jo's A4

Hi all! I am new to this forum and i'd like to thank the people that created it because it helps a lot of folks out there.

To begin with, I have a 1997 audi a4 1.8t, aeb engine 5 speed.

Never had a problem with it in 2 years, until now...

I am posting a new tread concerning missfire problems because i have NOT found anything like it or similar in every audi/vw forum ever...

It started about 2-3 months ago, I tested compression in all cylinders just because i was bored and i had a gauge in hands and the time to spare, car was running fine, it has all the maintenance from last winter done, it has 260k's now so yeah, i just wanted to see the compression, turns out to be 180 on all 4! great news.

But for some odd reasons, when i plugged everything back, cylinder 3 was missfiring..CEL flashing, so yeah i scanned the codes, only one was p0303, cylinder 3 missfire, changed spark plugs the same day, nothing, swapped injector, bought brand new ICM, cause i know they are POS! Nothing! still cyl.3 missfiring,swapped coils, tested continuity in all wires coming from ECU to ICM then ICM to Coils. Good continuity, but still number 3 running like crap, so i said go big or go home.

The last month i just did a complete rebuilt of the engine,i didnt touch the bottom end tho, it was clean and didnt knock, no loose whatsoever in piston/wirstpins, brand new head gasket and everything, had a little problem with timing belt tho i ordered a 152 theeth instead of the 153 one, should of looked it up before hand,brand new water pump,every seals etc..

Now, i am getting 200 psi per cylinder , but still the @!@#$@#% cylinder 3 is making weak to no spark... like am i missing something!?!?! ill send that car to research in paranormals!!

Well now to make it short for the end, i have the whole engine wiring on the floor and ill change the whole coil pack plugs/wires etc.. then next week ill buy vcds and a new ecu after that I'll give it to research i swear it impossible.

the only thing i could find about missfires on the b5 was ICM/bad coils/wires/ecu.. now i am at the ecu and after that i dont know what to do.. if someone in this world could help me find the light (spark) i need in my cylinder 3 it would be the best day (year) of my life! And also i forgot to mension, the ecu is chipped by myself stage 1 18 psi but its still starting and running just need spark on cyl.3.


Thank you for any help I get and god bless you guys!!!

Prospeeder

well its common the electrical connectors on the coils themselves go bad, you can buy repair kits to fix them.

Jo's A4

You mean the 3 pin connector that connects to the coil? I am re-wiring the whole thing from the ECU to the coil right now,I`ll put that bird`s nest back in the car tommorow and try it before buying another ECU, to be sure, its 150$ i can save if its just the wires/connectors , but lucky like I am, it wont do anything... might aswell buy an ECU and reprog it to my car.I thought these cars had something else then the ICM giving spark from the ECU but nope, Its all ground I think, so i`ll look ground connections too while im at it. Thanks for the input tho, greatly apprecited.

oceanbreeze

The ground connection on the valve cover came to mind when I was reading your post, but it's a bit of a stretch when it only happens on that cylinder. I'd test the wires to the coils.

Good luck. misfires can be a pita.

Jo's A4

I found the problem!!! but not the cause... My ECU is short to ground on the cylinder 3 pin.. That means i have constant mass going to my ICM, so the ICM just burns automaticly. I dont know what caused it, its really weird, but 12V test light,clip it to possitive side of battery and look the output of the ICM , light flashes and engine lowers in rev because you take all the juice going to the coils, my number 3 doesnt light up at all and on the input side (5 pin side) number 3 as constant light (ground) and all the others wires have signal ground.

This is a weird one and ive never saw that before, ECU shorting ICM ..

Anyway i hope this helps other people diagnosis in findind missfires on b5's after changing ICM,Coils,Wires and nothing changes.

Thanks for inputs guys!