Cylinder misfire.

Hi guys, hope i can get a answer to this question. I have a very small, (slight) misfire in 1 or more cylinders, it happens at any steady rpm i have no clue. Is there a tool or a way that someone can locate the cylinder (s) that it is happening in? Thanks for any help.

 

If you have a colourtune could you see with that?

 

how slight, like one misfire per second? one per 2-4 seconds?

 

you could try a set of these, they're not expensive, they fit between the sparkplug and the cap, and give a visible indication of the spark in the plug, though i had to modify mine because most xj sparkpugs dont use the caps, so i cut the caps of the top of the "testers" ,and fitted some 4mm threaded screws, to fit the caps
https://www.machinemart.co.uk/p/laser-2780-high-tension-lead-spark-tester/

dunno if they are available over there

 

I didn't have an actual misfire on the GS, but it wasn't quite right.
Yesterday I recieved one of these open gap testers and was able to find out what voltage each coil was putting out.
It's not exact, as the ability to leap a given gap depends on humidity and temperature, but it showed that coil 1/4 was approx 20kV and coil 2/3 was about half that.
I found the cause almost immediately, a crusty bullet connector on the LT side.

 

thats a nice simple piece of kit Dave. where did you get it?

 

It does its little puff once every 3 to 5 seconds. I'm liking the info you guys are giving me, thanks.

 

Straight off Amazon...
https://www.amazon.co.uk/dp/B06X9RC3PF

 

Is the misfire occuring at startup from cold, or hot or both?

 

The misfire will happen at anytime the rpm"s are steady, hot or cold, low or high rpm. Dave that was shipped this morning should arrive on the 3rd. I ordered the high tension tester that bensalf showed also. I have a coulortune so maybe i can figure this out. I will update later.

 

My thought was an IR temp sensor diected onto the headers - I guess it would need to misfire badly though to show much difference.

 

Is that causing an issue or your just looking for perfection?

@ 4000rpm that is 66.66 revolutions per second which is 133.33 sparks per second so a misfire every 3 seconds is 1 misfire per 400 good ones.

 

I was looking for a totally smooth sound ( perfection i guess ) I found the#3 cylinder was the culprit. #1,2,and 4 was shooting a spark 6 plus mm. and #3 could only shoot one about 4 mm. using the HAOSHI ignition spark tester. I took the #2&3 coil pack off and tested. Primary side was in spec secondary in spec also, but i found some dirt in the primary female connection so i cleaned And wham, bam, thank ya ma'am it runs as smooth as Tennessee whiskey. Ok ill stop. Thank you all for all of your ideas and advice.

 

You have given hope to many Dirt/corrosion = resistance
Good find

 

.. ok so can any smart chap explain how this fault on the primary only affected #3 plug/HT and not #2 also?

 

Thats a good question. It might not be the dirt in the connection. I wonder if I tweaked the spark plug wire possible bad connection at the coil. Its running great.