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Discussion Starter #1
Ok, a weird one here. Yesterday morning in my way to work, my idle gets significantly rough, and the CEL is blinking away. A couple miles down the road, and the problem vanishes. No CEL, no rough idle, smooth sailing!
Well 12 hours later I’m on my way back home, same deal, rough idle, blinking CEL. I swing by an O’Reilly’s and get my code read (and my car eye-humped by the staff) and they say P0302 cyl 2 misfire.
I get home and hook my reader up to it (an old Auto Enginuity) and I get P0302 and P0304. Ok so driver side of the motor.
O2 sensors were reading fine, but I notice my Absolute Manifold Pressure was only reading 11 in/hg.
unfortunately it started snowing so I had to retreat inside.
Previously I noticed my idle would drop down significantly at a red light, sometimes stalling, and researched the Idle Air Control Valve is a known culprit, so I do need to get new gasket and try a cleaning for that. Is it possible that my issue is related to this?
I’m also fighting an oil leak that according to previous records is likely from the oil cooler. I have the seal already and an oil change is due.
What else should I look at on the driver side of the motor?

2002 WRX, bone stock, minus stereo. 160K miles.
 

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For the oil filter housing O-ring use a deep socket 24mm to remove the housing and move it gently and you may not have to loosen the coolant lines at all.

For the idle drop and problems on right side check the IACV as you planned because it’s cheap and easy but I’d suspect the fuel pressure regulator there near the manifold.
 

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Discussion Starter #3
Fuel pressure regulator, I’m assuming the vacuum supply for it is on the DS of the intake? That would make sense. (sorry I literally just got this thing and am still figuring it out)
 

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Yes it's hooked up to vacuum on that side. If the vacuum line is faulty you may get a "lean" misleading fault code PO171. However if the regulator itself is faulty you may get the symptoms that you are describing -- except if you don't. It's a guess but worth a look.
 

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Discussion Starter #6
Ok, so a small update. Checked that vacuum line. While it was cracked and old, it wasn’t the source of the misfire. Fortunately I had some MB diesel return hose laying around (same size) and was able to put it back together.
I went ahead and checked the IAC, it seemed OK, not cruddy at all inside. Cleaned it out just the same. Gasket swelled and I couldn’t put it back together, paper gasket (homemade) won’t seal and I can hear it ‘hiss’ so I’m off to get a replacement.
Did notice something else, the hose after the MAF to the turbo had some cracks in it. I’ve read that this can trigger codes. I’m also smelling gas from around the regulator area, so maybe it’s bad too. Soo, time to get a fuel pressure tester to verify issue.
Also, what are people doing for replacement air hoses? While I want to keep this one stock, I’m not against upgraded components that can last longer and/or handle heat better.
 

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The IACV O-ring must be replaced new, yes.

Fuel smell around the FPR can be the FPR or the fuel lines. The former is easy to fix but the latter requires removing the manifold and fitting a new hard line and soft line redesigned by Subaru. Any dealer will have a kit.

If it’s the turbo inlet you are talking about, they crack and cannot be replaced with an authentic part unless the manifold is removed. There are imitation parts available that are silicone and can be squeezed in without removing the manifold but those will make the car illegal. The imitations all claim performance improvements.

Removing the manifold will require a new set of gaskets also.
 

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(I can’t se your video).

However an inlet tear will make the car run crappy and not hit boost but in my experience won’t cause the CEL codes you have. It may not be the source of your problems(?).
 

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Discussion Starter #9
No telling. I cleared my codes and waited for the light to come back on. Didn’t take long. Only have a P0302 now, p0304 vanished. Took a screen shot, seems clear I have a vacuum leak somewhere too. Thinking I need to get the Subaru package for my AutoEnginuity for more in depth monitoring. New gasket and cleaning the IAC helped with the choppy idle, but it’s still not normal. Looks to be original part, but the electrical plug ‘lock’ broke. Old plastic :( New one won’t hurt and is probably going to happen sooner rather than later.
I think I’m going to cave and purchase an ignition coil for #2. Wouldn’t hurt to have a spare. I saw some nice looking silicone hose kits on Amazon that I might get, either in black or blue.
As far as being street legal, I’m in Georgia, where emission inspections consist of a visual for the cat, testing the fuel cap, and plugging in the OBD. I’ve run ‘illegal’ CAI and Weber carburetors before and passed. They only care what it says on the screen. Hell, my hollow cat 95 Civic passed because the sniffer said it was good.

 

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If it's a coil causing the misfire now, that doesn't explain why there were two misfires previously. However let's say that it is a coil. If you swap coil positions you ought to be able to get the misfire code to follow that coil also. (Granted, doing so costs time and anything plastic you even look at funny will disintegrate before your eyes from old age and heat cycles, so there's a risk with everything). Good luck!.
 

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Discussion Starter #12
Ok, so I had a busy day. First off, the hoses for the oil cooler are a PITA to get off, especially with those heat shield spring clips. Seal didn’t look bad, put new one on anyways, it got tore up when I was fighting the hose clamps so I had to put old one back on.
went on to the coils, swapped 2 and 4 around. Turned car on after oil change was finished and everything hooked back up, and idle was smooth as silk! Guessing one of the coil connectors came loose? No telling, I’ll take the win.
I will start new thread about possible new oil leak source, and come back here if the miss returns.
 
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