Random multi-cylinder misfire code...help!

[Boxer12]

After installing Belanger headers and exhaust (battery disconnect) in 09, I am getting random multicylinder misfire. You can hear the valve clatter which is very audible on idle. Car has Mopar PCM, so it should adjust to the bolt ons, right? I have double checked all connectors, plug wires, etc. Nothing seems askew. Does the PCM need to be reprogrammed? That's all I can think of. I hope not. I have the OEM PCM, should I try swapping?

 

[Martin]

Weird - almost sounds like your lifters are full of air and not pumping up. Sure you have enough oil in it?

 

[Boxer12]

Didn't let any out...but you think it could be a lubrication issue? Oil pressure looks normal.

 

[fastmd]

Did you install the PCM, or did the dealer? There is a specific install via the dealer computer which has to be done the first time.

 

[Martin]

The combination of misfire along with valve clatter would make me look at the lifters first. It's a bit strange because there isn't much you can do to the lifters during a header install that would cause them any problems unless you left the valve covers off after starting it up and let all the oil fly out. You'd know it pretty quick if that was the problem though. While it doesn't affect the valve clatter, did you check the O2 sensor leads? A bad connection, busted O2 sensor (or one that got really contaminated during install), or grounding O2 lead would cause a random misfire. Theoretically, if the O2 sensor is messed up, you could be hearing some additional noise from your injectors if the computer is making them do weird stuff. It could also be a combo of different problems - bad O2 sensor and loose manifold bolts leading to misfire along with clattering noise.

 

[Boxer12]

Wouldn't an O2 sensor prob trigger a specific code? Not getting one, just the aforementioned code.

 

[Boxer12]

Did you install the PCM, or did the dealer? There is a specific install via the dealer computer which has to be done the first time.

The dealer installed the PCM, and the car was running fine before the header install. I did have to disconnect the battary, so maybe it wiped?

 

[Martin]

Wouldn't an O2 sensor prob trigger a specific code? Not getting one, just the aforementioned code.

That's an area where my knowlege goes into the grey area. Whenever I see multi-cylinder misfire, I start thinking about what would cause the computer to think multiple cylinders are misfiring at the same time. That's going to either be a bad timing chain or otherwise bad camshaft timing, massive fuel injector failures (not likely unless the PCM is malfunctioning big time), bad lifters (usually from low oil pressure), or bad O2 sensor (since they look at the whole bank of cylinders and the computer can't differentiate which cylinders might be screwing up). If the O2 lead got scuffed or broken, it could show a multiple cylinder misfire from grounding out to the frame on occasion or otherwise losing continuity. On new cars, it's really hard to say without digging in...

 

[vipernut94]

I got a cylinder 9 misfire code after about 70 miles of driving my ACR, and it went into limp mode. Took it back to Roanoke, and Dave (Viper Tech) installed a new cam position sensor, and I haven't had a problem since. I have seen some other threads that mention faulty fuel injectors and/or cam position sensors as possible problems. Is your car going into limp mode?

 

[SilveRT8]

I have seen some other threads that mention faulty fuel injectors and/or cam position sensors as possible problems. Is your car going into limp mode?

My Viper tech told me they change Injectors stamped #7278 on '08 models for giving the P0300 random misfire code.

 

[Boxer12]

Not sure if the car is in limp mode, I haven't tried to drive it except in and out of my garage. I also haven't tried to rev it past 4k. It did give a #9 misfire code initially, as well as random multicylinder code, but the #9 misfire went away after we cleared it. Its an 09, so I thought the injector issue wouldn't apply. Strange coincidence that it throws codes and goes haywire after battary disconnect?

 

[Boxer12]

I guess I will try putting the original PCM back in and see what that does. I don't know what else to do except haul it to the dealer.

 

[Steve-Indy]

I'm not sure that just any C-J-D dealer can get the new Mopar PCM installed without issues.

Your injectors have two small rows of numbers on them...check to see if they happen to fall in the 72(or 73) range mentioned above (second row ofnumbers). If you need the name of a good Viper Tech, call me.

 

[Boxer12]

I'm not sure that just any C-J-D dealer can get the new Mopar PCM installed without issues.

Your injectors have two small rows of numbers on them...check to see if they happen to fall in the 72(or 73) range mentioned above (second row ofnumbers). If you need the name of a good Viper Tech, call me.

Checked. No, they don't.

 

[Martin]

I guess I will try putting the original PCM back in and see what that does. I don't know what else to do except haul it to the dealer.

If you do take it to the dealer, it's probably wise to take that PCM out just in case. Unless you know your dealer really well, there's a chance they might give you a hard time about the PCM and warranty service on anything connected with the computer. I haven't heard any stories of that happening yet, but I wouldn't want to be the first one to have to fight that battle.

 

[Boxer12]

Changed back to orig PCM, it purred for a minute, then started chattering and then CEL ....same story. I guess we are going into the trailer and going to visit our local (60 mi) Viper Tech. Bummer.

 

[Steve-Indy]

Anything new ?

 

[Boxer12]

Turned out to be just a bad connection on #9, which is tricky to get on right because the connector is shorter than the rest and the heat shield impedes a good seat on the plug. Have to push the connector actually through the heat shield until the bottom of the connector is flush with the bottom of the heat shield, and press on with gorilla fingers.

 

[Steve-Indy]

Good to see you today, Jim. Your ACR is stunning!!
And, it really "hauls Asp" on the track!!!