EDIT: Post #3
Hi all !

I have read through a lot of misfire threads on the forum but I am starting to get confused so I wanted to post and ask for some help. I do apologize for another misfire thread.

I bought a 2008 GSR two weeks ago and recently I have started to notice a small misfire at idle. There is no CEL but I plugged in my scan tool just to make sure. The ECU is throwing a P0300 only (I will have to check to see if the CEL bulb has been pulled out).

The car has AMS SRI, UI, FMI, and LI. Ported stock TB, IM, and EM (ceramic coated). MAP DP (ceramic coated), T1R resonated TP, Specialty-X CB. It also has a higher flow Walbro fuel pump and GrimmSpeed 3-port EBC and Pro tuned by Cobb Plano with Cobb APv2.

A week ago, I replaced the spark plugs with NGK ILKR8E6 and torqued them to 10 ft/lb. I did not check the gap but it is supposed to be 0.024 in according to NGK's website. I am not sure if the misfire was present before I changed the spark plugs. I cleaned the MAF and air filter but it did not help. I wanted to clean the IACV but I don't think this car has one ? I will clean the throttle body Sunday.

I just went and took pictures of the spark plugs. They were pulled out after the car had cooled down from being driven normally. I was wondering if you guys can take a look at them and tell me what you think. I'm not very good at reading plugs. It kind of looks like the engine is detonating from the specks on the insulator and also colder plugs are needed because the electrode plating is burned past the curve to the vertical portion.

Also, if assuming its not caused by the spark plugs, what should I check next after cleaning the throttle body ? Spark plug gap and compression test ?

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I really appreciate your time !!

 

Your plugs look ok... I would suggest hitting up Cobb and seeing if they can take a look at your tune. There might be a little hiccup in the tune.

 

Evol Xenius, thanks for your response !

I got a chance to drive the car late last night and the misfire at idle was gone and so was the p0300. I'm not sure what happened. The only thing I did was take out all the spark plugs, take pictures, and put them back in. The only difference is that this time I torqued the plugs to 13 ft lbs instead of 10 ft lbs because since the washers were already crushed, once the washers contacted, the torque wrench clicked and I was afraid it was too loose so I set it to 13 ft lbs to thread it in like 5-10 more degrees.

Maybe its actually because my spark plugs weren't torqued enough ? I will see if this problem comes back. I'm also still going to do a compression test to find out the general health of the engine.

 

Do you have a Wideband and boost gauge installed? I would check what your readings are at idle/cruise before you do any WOT runs.

 

I have a wideband and boost gauge and both AFR and Boost are reasonable. Its been months and the misfire has not come back. I am going to attribute this to spark plugs that weren't torqued enough. Thanks everyone for the help.