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Discussion Starter · #1 ·
hi all

I've recently built my engine with vitara pistons aftermarket rods etc. However since then I have a strange issue with my idle, I do not think they are related though.

So the problem seems to be with Cylinder 2 on my JDM D15b Vtec (vtec is currently disabled)

when it idles it has a pretty bad lumpiness to it which makes the exhaust puff, and rattle I have a straight through powerflow 2.5" exhaust. This goes away if I unplug the cylinder 2 lead. I've swaped over the dizzy rotor cap and lead with others I had that seemed cleaner but no difference, well might be a bit smoother but still lumpy.

I cleaned all my injectors the other day with the carb cleaner and hose trick all were spraying a good pattern.

I'm pretty sure I have no vac leaks as I cannot hear any and no matter what I unplug it does not get rid of the lumpiness but does change RPM as you would expect.

What could be causing this issue? Could it be my rotor arm? I does seem to be spark related although cylinder 2 seems to be getting a good spark when I take the lead out and put a spare plug in it, certainly made my hand all wobbly haha (I know not sensible).

Any thoughts or routes for investigation people can think of would be great, as I say it seems to drives ok.

Thanks in advance
 

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check spark plugs

check compression

if pulling the plug wire from cyl2 has that effect, its fuel, compression, or spark related
 

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valve lash would not cause a lumpy idle, yet drive well.

this is why a compression check is required to check part of the physical health of the motor
 

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was it too tight or too loose?


my 2013 Fit was loose on intake and tight on exhaust, and the car idled and drove fine. set to spec on all 16 valves, and she got better gasmileage, and better performance
 

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Discussion Starter · #7 ·
Hi, valves have been adjusted to spec, plugs have been swapped around but I can try another one, the spark seemed strong when I was jumping it from a plug to the chassis.

Compression came out as 160 ish on all cylinders, loads low than before but I have new rings and I'm guessing that's the whole idea of low compression Pistons :)

I need to swap the injector with another cylinder and see if the issue moves cylinder too
 

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Discussion Starter · #8 ·
Hey, thought I would report back, swapped my injectors over from cylinder 1 and 2 which made no difference.

So I thought I would check my spark plugs again, so I swapped cylinder 1 and 2's plug and the issue moved to cylinder 1. Seems that was a screwed spark plug very weird.

Car is now idling like a dream, thanks for the help people always a great bunch on here.

Now I just need to crack on with tuning and breaking in my engine.
 
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