2008 Low rpm Sputter

[lmcgrew79]

2008 with mopar pcm, high flow cats, catch can and corsa exhaust. Around the 1800-2200 rpm mark the car sputters for a bit then goes, more in light to mid throttle applications. It seems like a misfire, but no codes are being thrown. Spark plug wires and plugs was changed last year, the car gets used on track quit often. It seems like it started on track during the warm up laps about a month ago, its not happening in higher rpms or on track at wot. Any Pointers on where to start.

 

[bluesrt]

sounds like possibly a bad spark plug, believe it or not (possibly)

 

[mjorgensen Woodhouse]

Also when you put in the catch can you probably plugged ports with rubber caps? Check to be sure they do not have small cracks in them bleeding air at low RPM. At WOT they may not matter, but lower RPM they could and may not throw a code until the tear is bigger. Anything else that could be wrong SHOULD be throwing some type of code...

 

[lmcgrew79]

I thought a plug would throw a code, but im gonna replace them here in a bit. Ill check the pcv hoses as well.

 

[bluesrt]

not if the sputter is not happening long enough for it to recognize

 

[bluesrt]

i had some old fuel in my acrx and it was sputtering in midrange also, ran about 5 laps at road america like this, was getting ready to put plugs in it, but could not find any, so i then put in fresh fuel (bingo)!!!! car never threw a code(it had a sputter misfire just like a cracked porcelin on a plug) plugs can get a hairline crack in them (very hard to see)

 

[mjorgensen Woodhouse]

Here is another possibility I solicited from someone that would know more then me lol.

Since its fine at higher RPM and WOT I wouldn't think itwould be a fuel delivery/pressure issue but never hurts to check. Sounds theengine runs fine in open loop conditions so may be on the right track inthat something is wrong in light load closed loop operation. I would look forsmall vacuum leaks, a small exhaust leak that could aspirate oxygen and foulthe O2 signal or even something wrong with an O2 sensor/signal. High flow carsscare me, they are not very robust, could be an issue there as well.

 

[lmcgrew79]

Thanks guys, i was thinking about just knocking out my cats, or does someone make a pipe.

 

[lmcgrew79]

Well i replaced the plugs and it fixed it. The plugs all looked ok except for cylinder #5, it had backed out, it was loose as soon as i put the socket on it. Wondering how long its been like this and how much compression i was loosing, or it just recently did it.
I went with the colder 7437's this time. We will see how they do.

Here is a photo with the exhaust/carbon on it.

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[Steve M]

That would certainly do it.