2003 Cayenne Porsche Turbo - Random misfires won't go away

[ValorianPrime]

Hi all,

 

I've not posted much but I am at my wits ends.

 

I have a 2003 Cayenne Turbo that has been running great with loving maintenance. Recently, I had a new coolant leak that I knew wasn't the pipes or the coolant tees as I had replaced them. I removed the intake plenum, found the leak was the small plastic "h" hose going to the rear of the engine under the plenum and replaced it. Everything put back together.

 

Then, I started getting random misfires P0300 errors with P0301, p0302, P303 and P0307. I replaced coil packs with aftermarket coils, no improvement. Thinking I got bad packs, I bought the Beru packs. Error P0300, P0302 and P0307 remained. Replaced spark plugs on cylinders 2 and 7. No go. I still have random misfires on those two cylinders and I am feeling beaten. Today, I thought I would try some injector cleaner, Chevron Techron, to see if it cleared anything up. Maybe an intake got dirty when I had the plenum off.

 

By the way, I replaced vacuum hoses also. No coolant leaks, and no vacuum leaks throwing codes. No P0200 codes either which would indicate injection issues. Each pack and spark plug made improvements, until now. No Durametric codes now except the P0300, P0302 and P0307. Rough at idle and can feel small misfires (is there such a thing as a small misfire)? I was getting this in shape to trade in come March. Now, I am despondent and don't know what to do next except possibly take it to Porsche and spend more than I will get back. Do I just need to try the injector cleaner and drive it a little more? Afraid to drive it too much.

 

Any good advice will be welcomed.

[JFP in PA]

I would check to make sure you reconnected the coil packs, both completely plugging them in, and not having crossed any. 

[ValorianPrime]

They are connected to wiring harness. The wiring is so tight that there is no way to cross wires from one cylinder to another, at least not on my Cayenne.They are all the way into the spark plug hole, so as best that I can tell, they are connecting to the plug. They are tight and the cover screw is tightened on the coil to the engine.


Sent from my LM-Q730 using Tapatalk

[JFP in PA]

Then using the basic rule to always go back to the last thing you worked on, the intake plenum.

[ValorianPrime]

My thought also. Will look at it this weekend and report back.