Cylinder Misfire - '06 Turbo

[datravler]

I've been battling a Misfire (P0302) for a few weeks on my 2006 Baja Turbo (76k miles). It began after I changed the plugs and has the engine idling horribly and often dropping to 500 rpm and dying when I push in the clutch at a stop light. I've reset the light between each of the steps below... the vehicle seems to run great for about 30-mins then the Misfire code hits for Cylinder 2 only.

1 - pulled all the the plug checked gap setting and connections
2 - swapped coil pack between cylinders 2 & 4
3 - swapped spark plug between cylinders 2 & 4
4 - placed original (pre-problem) plug back into cylinder 2
5 - verified clicking sounds on all injectors with stethoscope
6 - Decided to reach out to Forum to plan next step

Any help is greatly appreciated...


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[Guacamole]

1 - pulled all the the plug checked gap setting and connections
2 - swapped coil pack between cylinders 2 & 4
3 - swapped spark plug between cylinders 2 & 4
4 - placed original (pre-problem) plug back into cylinder 2
5 - verified clicking sounds on all injectors with stethoscope
6 - Decided to reach out to Forum to plan next step
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Hey there. I suspect you have a vacuum leak. Check the vacuum hoses for any cracks or looseness.

[datravler]

6 - Decided to reach out to Forum to plan next step
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Hey there. I suspect you have a vacuum leak. Check the vacuum hoses for any cracks or looseness.

I gave it a good try on checking for a vacuum leak. Sadly, I was unable to locate any problems...
7 - Visually inspected all vacuum hoses
8 - Sprayed water around the injector area and heard nothing while running
9 - Sprayed starter fluid around injector area and no rpm change
10 - Pulled plug and soaked cylinder for 30-mins with Seafoam using a long funnel
11 - Put new plug back, reset code, ran off all the mosquitos nearby... took the Baja for a spin and code return for Cylinder 2
12 - Back to Forum for more help


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[Guacamole]

Are you using 91 octane gasoline? Using a lower-grade in the turbo models will cause misfires.
And thus is my extent of knowledge of this issue, sorry I couldn't be more help.

[datravler]

Ah... hadn’t tried the higher octanes! Guess it just took a while to start acting up. I really appreciate the help! I’ll add an additive to the tank and report back.


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[Guacamole]

Yeah, you HAVE to use the 91+ octane gas in the turbos. These turbo engines operate at a higher pressure than the regular NAs, and thus using lower grade fuel will cause it to ignite early, causing misfires. Continuous use of low octane fuel in a turbo Subie (that isn't direct injection) can risk engine detonation.

[datravler]

Yeah, you HAVE to use the 91+ octane gas in the turbos. These turbo engines operate at a higher pressure than the regular NAs, and thus using lower grade fuel will cause it to ignite early, causing misfires. Continuous use of low octane fuel in a turbo Subie (that isn't direct injection) can risk engine detonation.

Added a bottle of Octane Boost and gave it time to work into the system. Today I received the normal P0302 code along with a Pending P0304 and a P0303. Only missing a misfire from cylinder 1 for the full roster. I'm thinking burn the fuel out and fill with normal High Octane fuel. I'm going to also swap 2 & 4's fuel injectors.


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[kamesama980]

Yeah, you HAVE to use the 91+ octane gas in the turbos. These turbo engines operate at a higher pressure than the regular NAs, and thus using lower grade fuel will cause it to ignite early, causing misfires. Continuous use of low octane fuel in a turbo Subie (that isn't direct injection) can risk engine detonation.

Added a bottle of Octane Boost and gave it time to work into the system. Today I received the normal P0302 code along with a Pending P0304 and a P0303. Only missing a misfire from cylinder 1 for the full roster. I'm thinking burn the fuel out and fill with normal High Octane fuel. I'm going to also swap 2 & 4's fuel injectors.


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slow down. run the gas out and top off with premium and give it a few days.

Let's get back to basics actually troubleshooting rather than shotgunning time and money and changing so much you won't know what helps.
Any headgasket symptoms? Have you done a compression check? leakdown test?

also, low octane gas preigniting or knocking is totally different than a misfire. one is early, uncontrolled combustion, one is partial or complete lack of combustion and the ECM can tell the difference. That being said, the damage from one (preigniting or knocking) can lead to the other (misfires) by way of physical damage. The engine will only throw a code for knock if it gets to extreme levels for long enough.You can blow an engine from a lot less knock than it takes to throw a CEL. for example: if the knocking event causes damage to the piston/rings causing reduced compression, the knock will go away due to lower cylinder pressures, probably before the ECM does enough about it to trigger a code. The ECM will think that pulling the whatever ignition timing that it did while there was knock did it. Computers are very smart but very short sighted.

[datravler]

slow down. run the gas out and top off with premium and give it a few days.

Let's get back to basics actually troubleshooting rather than shotgunning time and money and changing so much you won't know what helps.
Any headgasket symptoms? Have you done a compression check? leakdown test?

also, low octane gas preigniting or knocking is totally different than a misfire. one is early, uncontrolled combustion, one is partial or complete lack of combustion and the ECM can tell the difference. That being said, the damage from one (preigniting or knocking) can lead to the other (misfires) by way of physical damage. The engine will only throw a code for knock if it gets to extreme levels for long enough.You can blow an engine from a lot less knock than it takes to throw a CEL. for example: if the knocking event causes damage to the piston/rings causing reduced compression, the knock will go away due to lower cylinder pressures, probably before the ECM does enough about it to trigger a code. The ECM will think that pulling the whatever ignition timing that it did while there was knock did it. Computers are very smart but very short sighted.

Slowing down... keeping in mind that each step I've made has been at least a 1/2 day between to monitor the changes and only performing one at a time. I haven't check compression yet, but do plan to check the fuel pressure in the morning. I am now on a full tank of 91 octane and notice the car runs great until it warms up and the cylinder misfires start rolling in! I had a set of codes for three of the four misfires, with cylinder 2 always leading the way.

I will also see about a compression tomorrow afternoon following the fuel pressure. Thanks for the ideas!


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[Pgazz]

I know this was over a year-and-a-half ago but did you ever figure out what was going on with the misfire issue? I'm having a similar issue. I did do a compression check in all the cylinders are about 150. So they are good. It happens with mine after the car warms up for about 5 to 10 minutes.

[ZUBAJA]

I suggest a compression check AFTER the engine has warmed up. Someone correct me if I am wrong, but don't these engines still need an occasional valve adjustment? I can't seem to find it in the scheduled maintenance, but from having a few apart, there aren't hydraulic lifters (at least not in the ones I have seen). A mechanical valve system at some point will LOOSE clearances and once warmed up, can suffer compression loss. Dennis

[kamesama980]

I suggest a compression check AFTER the engine has warmed up. Someone correct me if I am wrong, but don't these engines still need an occasional valve adjustment? I can't seem to find it in the scheduled maintenance, but from having a few apart, there aren't hydraulic lifters (at least not in the ones I have seen). A mechanical valve system at some point will LOOSE clearances and once warmed up, can suffer compression loss. Dennis

That would come out in the compression/leakdown check as a leaky valve and is actually what I would have suggested next (compression check, check valve clearance)

The clearance is adjustable for a reason. flat shims and buckets last a long time but they can go out of spec. Especially with a touch of neglect and a wiped cam lobe.

[ZUBAJA]

You know, I wasn't even thinking about the buckets and shims (loads of fun - been there, done that) because of it being a turbo and the DOHC. I was thinking along the lines of rocker adjustment (I guess more non turbo). But that (compression check and valve adjustment) is always way up there on rough running diagnosis - especially when hot. Dennis