Ok so I went through the process of installing a new OE thermostat housing since my split and was leaking at 54k miles...typical from what i've read on the forum.

Hooked every sensor back up, vacuum lines...etc etc. But now I am only getting 2.9psi of boost...unplugged and rechecked all the sensors. The only thing I can think of is the two vacuum lines that run back behind the intake must have come unplugged back there. Any idea exactly where they plug into?

 

Well after putting a few miles on it with it running perfectly fine...except the low boost. I got a "partial engine power" warning light and erratic idle along with an audible vacuum leak from somewhere behind the intake manifold. I'm guessing I must have pulled a vacuum line loose from back there somehow doing the thermostatic housing. Have the car in the garage cooling off now before I investigate further.

 

Ok have things apart again...maybe i switched the vacuum lines...there are the two small ones, one goes to the cylinder head, the other to the turbo...which goes where?

 

Have a photo for reference? There's several lines in the area.
If you have more details, I can help you out this evening.

- Erik

 

Thanks, but I figured it out! Those lines were fine, the two vacuum lines that connect down underneath the intake manifold had come off completely...what a PITA to get them back on! My warning light is gone, but it's still not running as smooth as it should so i'm thinking there is another small leak somewhere else.

I'll do some more troubleshooting tomorrow. It runs fine under power now, and I have full boost. Just a slightly rough idle, and at cruising speed it's not as smooth as it should be.

 

disc your battery and hit the brakes a few times to reset ecu.

 

Did that, also reset with the Accessport...weird thing is now i'm throwing a check engine light. But there is no code showing up...grrrrr.

Only runs well under heavy load/boost. Idles rough and runs choppy under partial throttle.

This is driving me absolutely nuts...maybe I reversed those two vacuum lines on the port under the intake. That was a PITA to do though so getting back in there is not something i'm looking forward to.

 

Ok so I finally borrowed a real code scanner and it was showing code P0300 (random misfire). Cleared it, replaced a couple vacuum lines that were VERY spongy...car was running about the same for a little while.

Then a short while later it started running like crap ALL the time. Popping and burbling/surging at any RPM under load or even just cruising. Now it's throwing a P0304 code.

Could all these things be caused by more vacuum screw ups? I'm going to try switching a couple lines around. The factory vacuum diagram is terrible...unless someone has a better one.

I know it has to be either a vacuum line...or heck even a connector plugged into the wrong wire or something. Just because it started happening ONLY after doing the thermostat housing install.

 

Ok have everything apart for the millionth time. Vacuum lines are fine, routed the right way and leak free...

So...maybe a bad coil? I pulled all 4 and the far right one looks quite "toasty" compared to the rest. Maybe it going was just coincidence timing wise with me doing the thermostat housing.

Or heck maybe my fuel pump is shot, but I don't think that would cause the problems. I think i'm going to get everything buttoned down again, swap the coils around and see if the missfire changes cilinders. I just cleaned the intake side of the head about 8k miles ago so I know it's not from carbon build up that quick.

 

Well...after all that. I took the spark plugs out just to see how they looked.

Plug in cilinder 4 was broken. Well...the ceramic part is loose and spins plus moves up and down, changing the gap as it wiggles. So that would do it...looks like i'm getting a set of plugs tomorrow.

Sad part is the amount of time I wasted, AND I just put these new plugs in over the summer lol.



The black ring is from that part spinning and leaving a gap, letting the combustion chamber pressure come up in between. Also explains that coil being "toasty" looking lol.

 

Success that you found the issue!
Even better you found the broken plug before other problems (like plug breaking into pieces, falling into combustion chamber) arise.
For record how many miles on the plugs? I assume they are the original set from the factory?

- Erik

 

That's the scary part these plugs had maybe 10k on them? I actually took one of the factory original plugs that I still had saved and swapped that in for now...those plugs had 45k on them. Seems to run great now, but i'll most certainly be doing a full set of new plugs and replacing at least the one boot/coil that took some serious abuse because of this.

 

What plugs (brand and model) were used?

Interesting; there's been people with failing OEM plugs too. Keep an eye on those.

Yes, definitely; please post updates if any if this continues.

- Erik

 

Hey Erik, I used the exact NGK stock replacement plugs. I ordered in 4 new coils from NAPA for less than the price of 2 new coils from the dealership. So I figure i'm going to replace all 4 coils and all 4 plugs.

I checked all 7 other plugs I have (the 4 original ones, and the 3 new ones that weren't broken) and they all seem fine. I called NGK today and spoke to customer service they are supposed to get back to me...not holding my breath though.

I'm not concerned about getting money back but if there is a build quality issue with some of these plugs it should be fixed.