P0302 and P0303 codes - vacuum line?

My wife was driving our stock 2005 LGT with 95k miles yesterday. She was accelerating on the freeway and the car suddenly lost power and CEL came on. She limped it 2 miles home. It now idles rough and obviously something is not right. I pulled the codes and it shows P0302 and pending P0303, which look like #2 and #3 cylinder misfire.

 

Since this came on suddenly, I'm hoping for something really simple like a vacuum line. Is this possible?

 

If so, what vacuum lines should I look for? A little research shows a blue T connector can have issues. I see a blue T connector just forward and below the intercooler. That one looks like it's connected solidly. Is that the right one? Any others I should look for?

 

I guess I'll have to take the intercooler off to check all the lines. Is that a difficult job? I'll probably change spark plugs at the same time.

 

Thanks!

This thread is a great place to start when chasing down vacuum leaks.

 

http://legacygt.com/forums/showthread.php/intake-vacuum-leaks-and-you-pics-inside-235626.html

Before I finished reading your post, I was thinking when were the spark plugs last changed. They should be replaced at 60,000 miles.

 

The timing belt is do also the car is 10 years.

 

The tmic is easy to remove, just do all you can not to change the clocking of the Throttle body hose. It can become a PITA quickly.

 

That hose likes to slip off the TB rather then come off the tmic.

Thanks guys, but whats a TMIC? -

EDIT: got it -top mounted intercooler.

I just got the P0302 code on the way back from the mechanic after getting a new PCV valve, plastic T vacuum tube piece (was brittle so they recommended replace), oil change and new AVO engine air filter. My car has always had a rough idle. I babied it after the code as I didn't have the AP hooked up and wasn't sure what was going on. Babied it the whole way actually as it never really had time to warm up fully before the CEL.

 

Since they just had all the vacuum lines apart I guess that is the most likely culprit? Should I clear the code and see if it comes back before taking the car back? I was going to clear the learning anyway due to the new performance air filter but now I am not sure what to do and cant contact the mechanic until Monday. Car seems to run ok other than the usual rough idle. St2 tune and up to date on all maintenance.

Ok so I cleared the code and learning. Ran it around for a bit and once it stopped trying to stall at every stop it seemed good. Will see if the cel comes back.

302 code is back again. Back to the mechanic to attempt to diagnose. Joy.

Yes. Vac line.

Mine turned out to be a bad coil on spark plug 2, as well as a seriously burned down #2 spark plug. Replaced all the plugs and coil on plug two and all is good.

 

I swapped coil 2 and 4 and the code changed from misfire plug 2 to misfire plug 4, which is how I figured out the #2 coil was the problem.

 

Good luck on yours, Wagonation.

Still good on the wagon now that the vac lines are sorted out. Runs great.

 

Unfortunately the GT sedan now has a stumble and P0171 lean left bank cel. Hoping that too is just a vac line issue. These cars are so needy.

 

Hey can I use my AP to clear the code in a car it is not married to or do I have to un-marry it first for it to work? I forgot to get the advanced auto guy to clear the code but with the sudden stumble it was pretty clear that something was wrong and not just a fluke code.

you cannot use the AP that isn't married to the ECU to pull and clear codes.

 

you can use a tactrix cable and rom raider to view and clear codes.

 

I'm replying because I've been chasing a P0303 that intermittently happens.

 

I've checked and resolved all vacuum leaks and there could be some still present (intake manifold gaskets) but i haven't actually changed any out yet due to time constraints.

 

I ruled out it being a bad connector (both 1 & 3 connectors broke due to being brittle) and were changed to new ones. Mine isn't a bad coil pack since I swapped them from 3 to 1 and still getting cylinder 3 misfiring. spark plugs were just changed out within the required interval so i don't think that's the issue but i'll take a look at it soon. Clear the code and i can go on very long drives and no CEL if i'm driving hard. The misfire happens at low RPM or idle conditions. fuel trim table is good and no huge amount of knock or timing corrections seen via LV.

Check the coils if connected good

Zip tie vacuum lines, and replace the blue T with the barbed T that Turkeylord sells somewhere on the forums.

 

Did you inspect the TMIC? Perhaps the end tanks have separated.

 

Another frequent point of failure that causes vacuum issues is the turbo inlet pipe. At 95,000 miles it if it's never been replaced it's definitely time. I replaced mine at 60,000 miles and it was already torn with a hole in it.

 

That being said if you're taking it to a mechanic, smoke test it until you track down all the leaks.

 

If you're doing it yourself, perform a boost leak test by plugging the intake hose with a spray paint sized can (any can will work as long as it fits, but is large enough to plug the hose). Remove the hose from the intake box, put a can of some kind in it, tighten the hose clamp around it, then blow into the small recirculating valve hose. You should be able to compress air into that space with your lungs kind of like a balloon. If it doesn't hold pressure then listen for the leaks. Rinse and repeat until you have no more leaks.