202 popping through exhaust at idle.
Posted 11 June 2021 - 06:04 AM
G'day guys, I need some help.
My engine is popping through the exhaust at idle. When I give it some throttle, it stops popping until it goes back to idle.
Its a newly built black efi 202 at 30thou with a m90 supercharger. I'm using a megasquirt 3 gold box for the ecu with a 36-1 trigger wheel.
9.2:1 compression roughly.
Xu1 grind cam
Running 100% e85, usually only 80% ethanol at my stations.
Yella terra 56cc alluminiumt head with 1.6 rockers.
Compression is rouggly 165 psi on all pistons.
I've checked that its getting spark with a check light. No 6 plug is black while the other 5 are normal. I swapped coils but no change, new leads amd plugs, but nothing.
I thought the rocker arm on no 6 exhaust might be hitting the rocker cover as it'd originally cover but I can't see any marks. I was thinking of.starting it without the cover but thought it might make a huge mess.
I'm running out of ideas. Any thoughts
Posted 11 June 2021 - 08:19 AM
How come you used a big cam designed for triples with a blower? Just curious.
Posted 11 June 2021 - 09:12 AM
Posted 11 June 2021 - 09:36 AM
I pulled it all tge way down to 12:1 to check that but that's total afr at the collector. It's odd it is just one cylinder.
Posted 11 June 2021 - 10:53 AM
Posted 11 June 2021 - 02:16 PM
Pull one spark plug lead or injector electrical plug of at a time and check which cylinder isn't working. Check for a dribbling injector, vacuum leak and spark at idle on that cylinder. Have a good look at the spark plug it should tell you part of the story. If you have a vacuum gauge put it on and make sure its not flickering at idle. I found a very weak valve spring on a engine that still had good compression on that cylinder, took me a while to find it as it was probably the most unlikely fault in my mind. However The first thing I would be looking for is a vacuum leak at the inlet manifold on that cylinder.
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