6.0 p300

[notagn]

Hey guys,

I am looking for some direction. I have a p300 code on my 2005 chevy 6.0. I performed a cam swap with the recommend springs. I can't seam to get ride of a random misfire witch seam to hit #7 the most. I have done all the usual checks. Coil swap, change of plugs and wires, double checked the valve lash. I sent a data log off to Black Bear that seamed to help a bit, but the miss is still present. The miss is not just OBD sensors but I can fell the miss as well. Any help or suggestions would be great. Thanks!!

[mag2555]

5 and 7 fire consecutively so 5 can end up making 7 run lean.

[CGT]

Is this a bigger than stock cam? Is the miss under load or at idle?

[tt 383]

Maybe look into vacuum leaks since digging into the engine, and then log or confirm running fuel pressure when started, running, warm and obviously when it’s acting up.

[Racer71]

Have you done a cam variation relearn? Not having done it can cause erroneous misfire detection. Are you able to watch them live and see which cylinders are counting the most misfires? Check the injector pigtails we have issues with them not making a good connection, the female side of the connection gets loose.

[dannobee]

Check to see that you don't have injectors 5 & 7 connectors mixed up. Pink on the power side and on the ground side, #5 should be BK/WH, #7 should be RD/BK.

[1980RS]

Clean the MAF sensor and check the cats on the truck. Watched a few techs struggle with random misfires that last one was for 3 months, the field engineer finally came out and sprayed the MAF and the misfires were gone. The other thing I have seen is non-ac delco spark plus cause misfires also.

[notagn]

The list of try's so far.
New MAF
Moved coils
New plugs
Crank to cam lean. This is an LS so the firing order is as follows.
1-8-7-2-6-5-4-3.

Thanks for the reply's so far.

[CGT]

Im still wondering if this is a bigger than stock cam, unless I missed it. And therefore overlap induced P0300's.

[notagn]

Im still wondering if this is a bigger than stock cam, unless I missed it. And therefore overlap induced P0300's.

The short answer is yes. The cam is larger then the stock cam. I can get the numbers this eaving. My understanding and it looks to me like a mild towing cam. That's what I asked for. The seller of the cam said no tuning should be required. He is very reputable so I trust his judgement.

[CGT]

Im still wondering if this is a bigger than stock cam, unless I missed it. And therefore overlap induced P0300's.

The short answer is yes. The cam is larger then the stock cam. I can get the numbers this eaving. My understanding and it looks to me like a mild towing cam. That's what I asked for. The seller of the cam said no tuning should be required. He is very reputable so I trust his judgement.

OK. I have had a 214-224 115 set PO300 codes before, yours may be milder than that yet. Its just a thought. And you are saying that you can physically feel the misfire under load? If so that would be less likely to be the cam...just thinking out loud. Any chance you got a questionable sealing valve job or valve guide issues?

[motionper]

carbon in egr valve causing vacuum leak

[CGT]

05 shouldnt have egr valve.

[notagn]

Cam spec's for ya L/C 114 ICL 110 ECL 118 Duration @ 50 212 and 218. Lift at cam is 316 and 312.

The miss is only at idle. Their is a miss for sure in the engine. I wonder if I change the what the detection for a miss in the computer will the computer stop making changes and the idle will smooth out?????

[CGT]

Cam spec's for ya L/C 114 ICL 110 ECL 118 Duration @ 50 212 and 218. Lift at cam is 316 and 312.

The miss is only at idle. Their is a miss for sure in the engine. I wonder if I change the what the detection for a miss in the computer will the computer stop making changes and the idle will smooth out?????

I think that's enough cam to trigger some random misfire codes(P0300) at idle...but shouldn't sound like a dead miss. Using software to ignore that trouble code will not change anything other than not turning your Check engine light on. Are you using hp tuners? Have you drove with the scanner on? Will it count up and acquire misfires while driving or only at idle?

I can see that cam using a little more timing and a little more throttle opening than stock for best idle...a long with a touch higher idle rpm.