Engine misfire

[Cooks]

Hi,

 

Wondering if anyone can help. I am quite sure I have a missfire at idle / low rpm. The idle sits around 750rpm and fluctuates every so slightly when sitting. If I blip the throttle to say 1000rpm the car vibrates, it also sometimes vibrates at idle also. Which would make me think there is a miss fire. Car revs and pulls well when driving. 
 

I cleaned the throttle body last summer with great improvement to throttle response. Checked all the hoses to throttle body and intake and all tight sprayed abit of carb cleaner on the connection and no change to idle. 
 

there is no check engine light on and I have plugged in a generic code reader and there are no codes at all. 
 

any ideas? 
 

thanks 

[flyingpenguin]

Good way to diagnose is to hook up a code scanner. Sporadic misfires don't show up as CEL immediately but will get stored in memory. Durametric is a good option.

[pgboxters]

Or you can spray water on the coils and that will show the bad one/s right away

Sent from my SM-G986U using Tapatalk

[JFP in PA]

If the coils show any signs of cracking, regardless of what they do when water is sprayed on them, I would can them and install new units.  Once they start cracking, it is only a matter of time before they fail...............................😉