P0300//mulitiple misfire

[hawaiih3]

1st time check engine came on was while I was in line at a drive thru so I ran a scan with a Gynesis and pulled P0303 and P0300 so I replaced all plugs
with iridium (denso)-cleared codes and ran another scan. No codes. However, the scanner can run live data stream and as I am running live data I can see mulitiple misfires and it records the count in history on each plug . But the misfires only occur during idle and not under load like cruising speed on the highway. for instance if i rev the engine like just tapping the throttle I can feel a hesitation of power and the live data reads mulitple misfire but then clears it self but no code or engine light comes it just continues to count and clear its self. I checked for a vacume leak found none, checked to see is the valve cover to intake box hose was cracked or loose and it wasn't. I replaced the # 3 coil, but still no change. There is no crankshaft sensor code nor camshaft sensor code, starts fine and runs fine but when I run live data I can see the misfires occuring. Anybody have any ideas on what is going on or lead me to possible cause?

JJ

[RubHer Yellow Ducky]

Dirty fuel, fuel filter, vacumn leak, gap, timing...

let us know...

[Big Dad]

What year is that beast and what engine do you have?

[hawaiih3]

Thank you for your input:


I have the 2006 H3 3.5L/L5 engine. Prior to code pop up I used Chevron fuel but always fill up with Philips 76, I did check for vacume leaks didnt find one ( I checked the air intake tube, the air box and the valve cove to air box hose), I just put in new iridium plugs and I did check the gap they were .043 (pre-gapped) which is where they should be but I went ahead and regapped them to .041 just to make sure but no change at all,I havent tried the fuel filter. The rpms on the live data stream show from 611 to 634 at idle it is not a smooth a steady graph reading and did find that to be odd. I have appr. 46k miles with no major mods except the K&N filter which I had in there about 1 1/2 years with no issues, and only use regular unleaded ,every once in awhile i do give her supreme but never had light pop up.
TY
JJ

[RubHer Yellow Ducky]

time to buy a new one...!

[Ryan Graham]

Head/valve problem? You'll have to do a compression and leak down test to verify. I had a P0300 and the dealership did an injector cleaning. The code hasn't come back, but the intermittently rough idle is still there.