So I have a code p0302 (misfire cylinder 2)
I replace the coil and the spark plugs and I reset the comp
but the next day light come out again the same code
do any of you guys have any idea what it is? or what can I do

 

YEAR & MODEL would be most helpful if you actually want help. I guees that you have an I5??????


Shall we assume that you know which cylinder is #2? Wasn't too long ago somebody with a question like yours did not know where #1 was and how to count the cylinders in order.

If you got that right, did you check the wiring harness to coil on plug pack #2 for any issues. Did you properly seat the coil on plug pack on the plug before tightening its fastener?

Easy stuff first.

 

2006 h3 and yea I think I know with one its coil 2 and when I was replacing the coil apparently before I bought they had the same problem but the replace the wrong coil, the replace the 4
and sins I was going to replace the coil I replace 5 spark plugs and the 5 boots with the little spring but I didn't check the coil wire.

 

i have the same issue, from the research it could also be injectors. i replaced the coil and plug in h3 cylender number 2 because i was getting the same code, i still get a shake and a missfire code for cylender 2 but about half the time it doesnt pop a code for it. any one have any suggestions?

 

I'm having the same issue. Replaced plug,coil pack,cleaned maf,cleaned throttle body,and ran injector cleaner (in a can). Anyone know if there is any serious issues that can occur if left as is?

 

Well after a lot of research gm has an issue with the head going bad on the 3.5s. For 2006 and it does exactly what all of our h3 s are doing. Fixed the coil, plug, injectors and cleaner and still popping the code. Apparently if your last six on your vin number is lower then 287000 they had issues with the head.

 

I have a 2007 and I get a cylinder #1 misfire but only seems to happen at times when I shut off the car and start it back up right away. I clear it and it doesn't come back unless I stop/start it or let it idle for a long time. I did the coil, plug, injector, cleaned throttle body, replaced MAF, new air filter. Idles at about 600 or so rpms but does feel rough at times. Just ordered a cam sensor actuator to see if that helps.

Been very fortunate with this truck. It has 215K miles and I monitor my gas consumption on every tank full. I average 16-17mpg but goes into the 15mpg range at times only during Winter.

Anything I can get the dealer to do at this point if I had the head issue? My vin's last six nuber falls under 287000.

 

The SN# extended warranty was for 2006s ONLY. The S/Ns affected is any 2006 H3 with 3.5L lower than 287591 .... the first one started with 100,001, your truck build date will be Nov. 06 or earlier. Got nothing to do with 2007s.

 

zx1100... the only thing that stick out to me that you missed was checking the Intake Manifold Bolts to make sure they are all tight. The vibrations of the I5s have been known to cause them to loosen and create misfire/rough idle symptoms.

 

Doc...now that you mention it, I do only have 2 bolts holding the manifold secure. I dropped one while removing never to be found but it seemed secure enough so I didn't bother replacing it. My VVT solenoid/actuator should arrive so I'll get that in right away and be sure to get another bolt for the manifold.

Thanks!