Ever since a couple weeks ago my car has been missing when it hits high boost...so about 16-22lbs. Took the car to VAST yesterday. We data logged it, then the guys went to work and re-tuned it a bit for fuel and did a little recoding of the ecm. Everything was perfect....until a couple hours later when it missed again and now the check engine light is on,scanned it, said it was P0300.. random misfire. Is it time for new coil packs??! The car has about 190,xxx on it. The plugs has been changed very recently.

 

From the sound of it, it seems Vast made sure the tune was running smooth with the right AFR's id say it's got to be something on the spark side. How are your plugs? Id pull one to see if its fouled. There are a couple pictures that explain how to judge and analize a spark plug may it be to rich, not enough spark and so on. I recently picked up an S4 so I dont know to much about these yet but just an idea.

Im not to sure how coil packs distribute spark for this car, But when I had my audi TT and I went big turbo I didnt have enough spark on full boost (30psi) it was blowing my spark out like a birthday candle.

 

what are the plugs supposed to be gapped at? is the gap different with higher boost cars?

 

The coil packs were actually recalled on that engine. Might just be time to replace them. Also a closer gap plug with a colder range might help.

 

Changed the plugs last night again...a couple that I took out, the porcelain was cracked a little and they didn't look too good on the tips..so with the new ones it hasn't missed yet! But ever sine then the car idles like CRAP! Ha its never done this before..just can't win! But a sidenote...props to VAST the lilttle tuning they did when I was there is wonderful,night and day!

 

And I had no idea the coil packs were recalled!

 

Yea, you can find information about it on google somewhere. If the porcelain was cracked it was probably due to heat assuming that they were not faulty. Have you done any fuel system upgrades? The kind of heat that it take to crack a plug could be coming from an engine running lean. At high boost maybe your injectors aren't feeding enough fuel.

Also, search google for spark plug engine diagnosis. If you have been going through a lot of plugs compare them to the pictures and see if you can find some clues there.

 

Ok thanks...and yes the car is a stage 3 it has 42lb "green monster" injectors I guess they call them lol and a 255 fuel pump I will have to look at the build sheet to give u more info