# p0301



## gmikel (Nov 10, 2010)

i have an 06 jetta 2.0 with 80k. love the car but have a reoccuring p0301 code. swapped coils and plugs and checked compression (160psi). scan with ross-tec shows an almost constant missfire in # 1 cyl at idle, i can't feel it in the car or hear it in the exaust. does not occure at any speed above idle. crazy as it sounds it goes away with a/c turned on. any thoughts?


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## gmikel (Nov 10, 2010)

any thoughts? measuring blocks show almost continuos miss at idle on #1 cyl., no miss under any other condition or with a/c [email protected] idle. car runs great but for the cel. exhuast lash adjusters, crudy valves, bad injector?


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## BlueJetta2.0T (Jun 30, 2009)

Maybe the time to clean your intake valves? Clogged intake valves will cause misfire at idle, especially when engine is cold and is an issue with DI engine.


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## DUBBERMK5 (Feb 9, 2008)

*y0*

ders a recall on the ign coils...call the dealer ask for info on recalls for your vehicle and give em your vin #...i just got mine replaced...bunch of recalls on our cars, check em out and den go from der...


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## gmikel (Nov 10, 2010)

*coils replaced on recall*

swapped coils and plugs1&2 @ onset of code, tested compression, good. will clean valves and replace #1 injector after mothers day. engine idled like crap a couple of days ago and now seems good as new. problem started when i put techron in 3 tanks of gas ago and am thinking maybe it was related.


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## chc-rado (Nov 20, 2008)

Most likely carbon build up on the valves. It's not hard carbon. More like soft gummy carbon (soot). If you have bore scope (video scope). You will see the black build up on the valves. It mostly causes rough idle in the morning. And slight misfires when warm. Only way to clean them is removing intake manifold. Cleaning the valves. Baking soda blast works wonders. In some cases, injectors could be the cause. Breather unit tend be go bad too and all depends on drive cycle( behavior) you drive the vehicle.


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## gmikel (Nov 10, 2010)

*free time*



chc-rado said:


> Most likely carbon build up on the valves. It's not hard carbon. More like soft gummy carbon (soot). If you have bore scope (video scope). You will see the black build up on the valves. It mostly causes rough idle in the morning. And slight misfires when warm. Only way to clean them is removing intake manifold. Cleaning the valves. Baking soda blast works wonders. In some cases, injectors could be the cause. Breather unit tend be go bad too and all depends on drive cycle( behavior) you drive the vehicle.


i'll have time after mothers day. will yank intake, clean valves and replace # injector cause i'll have it apart. think if was anything else it would be random missfires instead of constant #1. will post after job is done.


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## gmikel (Nov 10, 2010)

*warning*

i've almost got it apart. pretty straightforward. however don't start until you have a long 10mm triplesquare. i have 2 shorter ones and there is not enough space for anything but the shaft of the triple square, so i'm waiting for a long set to be delivered. you cannot just go out and buy one at your local parts store or tool outlet.


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## gmikel (Nov 10, 2010)

*apart at last*

long triple square is the ticket for the manifold brace. apart in no time.

anyway ports were so gummed up i'm surprised it ran at all. solid from the outside wall of port to the valve stem. valve themselves were not as bad as some i've seen here. almost done scubbing. my guess is that it will run much better when i get it together.


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## gmikel (Nov 10, 2010)

*done*

idles smooth as butta. not a bad job with right tools. just takes patience, i kinda picked at mine a little at a time.

some observations, the port bowls were gunked up pretty badly, on a couple of valves the buildup extentend from port wall to valve stem in upper section of bowl, gotta cause problems.

funny thing, the injector i planned on replacing came out with manifold, an oman, maybe.

on test run after completion the idle was improved so much i thought it stalled coming to a stop.

who knows, a bad injector or gunk? doesn't really matter all's well. mike


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## rhcp4life (Apr 12, 2011)

Im having the same issue with my GF's car ill call the dealer and check the vin for recalls


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## gmikel (Nov 10, 2010)

*recalls*



rhcp4life said:


> Im having the same issue with my GF's car ill call the dealer and check the vin for recalls


the only recalls i'm aware of for misses involve the coils. there are some tech bullitins that deal with misses. all deal with checking coils, plugs and compression. after that you're left with fuel injectors and on some cars fualty lash adjusters on the exhaust side. good luck.


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## rhcp4life (Apr 12, 2011)

gmikel said:


> the only recalls i'm aware of for misses involve the coils. there are some tech bullitins that deal with misses. all deal with checking coils, plugs and compression. after that you're left with fuel injectors and on some cars fualty lash adjusters on the exhaust side. good luck.


Yeah, her car had the same code 2 weeks ago, cleared the code and changed her plugs. but it came back, ill check to see if she had the coils done on recall.
idk if it has anything to do with it but after I clear the code, the following readiness monitors comeback incomplete

the Evaporative system monitoring
catalyst monitoring
oxygen sensor monitoring
oxygen sensor heater monitoring


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## gmikel (Nov 10, 2010)

*readiness codes*



rhcp4life said:


> Yeah, her car had the same code 2 weeks ago, cleared the code and changed her plugs. but it came back, ill check to see if she had the coils done on recall.
> idk if it has anything to do with it but after I clear the code, the following readiness monitors comeback incomplete
> 
> the Evaporative system monitoring
> ...


it's normal for the readiness codes to be incomplete after a reset. takes a few key cycles for them to reset.


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## gmikel (Nov 10, 2010)

*misses*



rhcp4life said:


> Im having the same issue with my GF's car ill call the dealer and check the vin for recalls


an after thought, try a bottle of techron with your next fill up. don't do it before a trip but rather before a series of short drive cycles. cleans better when it sits in the injector for a few hours.


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## rhcp4life (Apr 12, 2011)

Called VWoA no recalls on the engine. Would a clogged injector cause the diagnostics to throw a misfire code? Wouldn't it give a code that cylinder 1 is running lean?


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## rhcp4life (Apr 12, 2011)

I'm going to try and swap coil 1 & 2 to see if it is the coil, I may put some injector cleaner in also


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## gmikel (Nov 10, 2010)

*just added pvc to list*

after idid the cleaning etc it ran fine for a day and start with the misfire on cyl #1 again. checked vacuum and found it to be 17 in., should be over 20 at idle. replaced pcv with updated one and vacuum jumped to 21 in.. thats the good part, unfortunately it still missfired. ran upstate for a day and on return missfire gone again. who knows


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## rhcp4life (Apr 12, 2011)

Have you figured anything else out on the misfire?


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## gmikel (Nov 10, 2010)

*seafoam*

just seafoamed we'll, seems better.


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## obdboost (Feb 27, 2010)

well if you clean the valves, swap the plugs, coils and injectors. might start looking at the lifters. there a tsb out on your car about that. feel free to pm me


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## gmikel (Nov 10, 2010)

*lifters*



obdboost said:


> well if you clean the valves, swap the plugs, coils and injectors. might start looking at the lifters. there a tsb out on your car about that. feel free to pm me


my vin does not fall in the group with the lifter problem. my problem occurs when warmed up, tsb is for cold start. not that it couldn't be a lifter. it runs great otherwise, so if i'm still having problem when it's time to do timing belt i'll look into lifters.

any suggestions are welcome.


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## rhcp4life (Apr 12, 2011)

Took our cars to the dealer for some recalls and what not. they ended up replacing a vent/purge valve for $180! the part cost 17...


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## gmikel (Nov 10, 2010)

*fingers crossed*

seafoamed again and redid throttle body adaptation over a week ago. light came back on at initial start up but when out on its own the next evening. so far so good.


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## rhcp4life (Apr 12, 2011)

Her light is back on... im kinda pissed they replaced it as it was not showing the p0441 code, back to the dealer..


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## gmikel (Nov 10, 2010)

*a week later*

it's back, gotta be a bad wire or the ecm forgot how to idle. going to repair (replace) wires and connector for # 1 coil. after that who knows. run great otherwise and i got it through inspection, so i've got a year to figure it out.


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## rhcp4life (Apr 12, 2011)

you dont think it might be a bad ground? idk just throwing out ideas. You say it only happens on start up correct?


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## gmikel (Nov 10, 2010)

*could be a bad ground*



rhcp4life said:


> you dont think it might be a bad ground? idk just throwing out ideas. You say it only happens on start up correct?


the thing i have trouble understanding is why it goes away a little over 800rpm. i have a ross tech and the missfire counts stop once the engine gets over 800rpm. i can lug it down to 750 rpm in gear and get no misses or wind the crap out of it. relacing wires will eliminate one more thing.


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## rhcp4life (Apr 12, 2011)

Any news?


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