JuicedH22 Posted May 29, 2013 Report Share Posted May 29, 2013 I dont anticipate much from ls1tech, but I thought maybe one of the experienced guys here might have seen something as weird/unique as this... http://ls1tech.com/forums/generation-iv-external-engine/1650508-2-8-cylinders-running-rich-misfiring.html I'm really at a loss here... Quote Link to comment Share on other sites More sharing options...
schmuckingham Posted May 29, 2013 Report Share Posted May 29, 2013 Are you coming off a fresh rebuild? I had a Honda motor do this on cylinder 4 and it turned out to be a soft sleeve/ unseated rings not allowing a full burn and running rich. Quote Link to comment Share on other sites More sharing options...
Cordell Posted May 29, 2013 Report Share Posted May 29, 2013 What are the compression numbers on those and few other cylinders? Quote Link to comment Share on other sites More sharing options...
Miller Posted May 29, 2013 Report Share Posted May 29, 2013 What are the compression numbers on those and few other cylinders? compression test: all cylinders 90psi first stroke, and 190psi on the 5th stroke Quote Link to comment Share on other sites More sharing options...
JuicedH22 Posted May 29, 2013 Author Report Share Posted May 29, 2013 Are you coming off a fresh rebuild? I had a Honda motor do this on cylinder 4 and it turned out to be a soft sleeve/ unseated rings not allowing a full burn and running rich. fresh rebuild, but no sleeving done, stock bore. If it were unseated rings, I would expect the leakdown to be low, which it was not... Quote Link to comment Share on other sites More sharing options...
schmuckingham Posted May 29, 2013 Report Share Posted May 29, 2013 fresh rebuild, but no sleeving done, stock bore. If it were unseated rings, I would expect the leakdown to be low, which it was not... I know it is weird but I had the exact same issue, stock sleeve was soft and 4 passed a leakdown but not compression. Quote Link to comment Share on other sites More sharing options...
accel_is_my_drug Posted May 29, 2013 Report Share Posted May 29, 2013 WHat intake manifold? need more info... Quote Link to comment Share on other sites More sharing options...
JuicedH22 Posted May 30, 2013 Author Report Share Posted May 30, 2013 not sure what the intake manifold has to do with it? but sure... FAST102 NW102 TB TR6 plugs TFS 235 heads, 12:1 CR flat-top wiseco pistons, rings gapped to 022/024 comp cams custom grind cam... 247/255 113+3 lsa, 25 degrees overlap... ls7 lifters, stock rockers... Siemens DEKA 60lb injectors, FAST rails Quote Link to comment Share on other sites More sharing options...
Mensan Posted May 30, 2013 Report Share Posted May 30, 2013 not sure what the intake manifold has to do with it? but sure... http://www.flowbenchoz.com/Smokey.htm The intake manifold determines how air enters the intake port and significantly effects atomization and flow, which has direct effect on combustion. If there is turbulence or a restriction caused by the manifold it will not allow as much air in, and fuel will still be added as expected for combustion at full expected CFM, which results in a rich mixture and incomplete burn. Quote Link to comment Share on other sites More sharing options...
gillbot Posted May 30, 2013 Report Share Posted May 30, 2013 Ported heads? Did they screw up the port job on the affected ports? Quote Link to comment Share on other sites More sharing options...
Cordell Posted May 30, 2013 Report Share Posted May 30, 2013 Do a running compression test on those cylinders and at least 2 others for comparison. It would show better if it has airflow problems to them, usually used to help diagnos valvetrain problems but in the case of a fresh rebuild it could be other things. It sure sounds like it would be poor airflow to those cylinders after you've moved other parts around and such. Short of setting up a dial indicator to check valve lift at those cylinders I'm not sure what else it could be that hasen't already been discussed. Quote Link to comment Share on other sites More sharing options...
accel_is_my_drug Posted May 30, 2013 Report Share Posted May 30, 2013 not sure what the intake manifold has to do with it? but sure... FAST102 NW102 TB TR6 plugs TFS 235 heads, 12:1 CR flat-top wiseco pistons, rings gapped to 022/024 comp cams custom grind cam... 247/255 113+3 lsa, 25 degrees overlap... ls7 lifters, stock rockers... Siemens DEKA 60lb injectors, FAST rails Crappily design intake manifolds can easily starve a few cylinders and let others get way too much air.. Usually half-assed aftermarket ones have never had a proper transient CFD done to see the airflow distribution along a bank while each cylinder is sucking in air. I would guess FAST would be OK, but I wonder how sort of taper that rolled runner design has between the front runners and rear runners, I suppose just because something is expensive, doesn't necessarily mean it is designed well... Quote Link to comment Share on other sites More sharing options...
ImUrOBGYN Posted May 30, 2013 Report Share Posted May 30, 2013 Hasn't been mentioned and since I'm not familiar with your particular branded modifications the the LS motor... How bout any of the coils not firing properly? I know you said no detected misfires, but that doesn't mean there isnt an issue of sorts. Quote Link to comment Share on other sites More sharing options...
JuicedH22 Posted May 30, 2013 Author Report Share Posted May 30, 2013 Intake isnt new, I had this intake on for 3 years.... and it never had a miss. The 102TB is new to the equation however, and I suppose could be part of hte equation... Though many many many people run a FAST102/102 set up, not sure how mine would be different.. Only way I can see it being the intake is if I had a severly ripped/torn gasket or it fell out and i didnt notice it... which is not the case... Quote Link to comment Share on other sites More sharing options...
JuicedH22 Posted May 30, 2013 Author Report Share Posted May 30, 2013 Also, as stated... I SWAPPED the coils... the misfire didnt change cylinders/go way/move... Quote Link to comment Share on other sites More sharing options...
accel_is_my_drug Posted May 30, 2013 Report Share Posted May 30, 2013 swap injectors next, and see if the misfire goes with them.. Quote Link to comment Share on other sites More sharing options...
Trouble Maker Posted May 30, 2013 Report Share Posted May 30, 2013 Is it a 'mirrored' set of cylinders i.e. the 2 back cylinders? Or two random cylinders? Quote Link to comment Share on other sites More sharing options...
JuicedH22 Posted May 30, 2013 Author Report Share Posted May 30, 2013 swap injectors next, and see if the misfire goes with them.. I did that... did you follow the link in the first post? lol Quote Link to comment Share on other sites More sharing options...
JuicedH22 Posted May 30, 2013 Author Report Share Posted May 30, 2013 Is it a 'mirrored' set of cylinders i.e. the 2 back cylinders? Or two random cylinders? Its cylinders 2 and 6, which are on the same bank/side of the engine (passenger) but not next to each other... ALTHOUGH they are next to each other in firing order, which may or may not be a coincidence... I will say, my prime suspect at this point is hte harness, which I fucked with while hte engine was out to relocate the coil harness connection. While I did not cut any wires ore splice anything... the wires were all reaaaalllly hard and 'stuck' to each other from years of heat... I do wonder if I somehow cracked a wire or something.... unfortunately a harness swap is a complete PITA for just 'testing'..... I want to see if there is some kind of scope I can put on the connections to measure what is happening electronically at the connections to the injectors and coils.... Quote Link to comment Share on other sites More sharing options...
gillbot Posted May 30, 2013 Report Share Posted May 30, 2013 Run a temporary wire "around" the suspected bad section if possible. Quote Link to comment Share on other sites More sharing options...
JuicedH22 Posted May 31, 2013 Author Report Share Posted May 31, 2013 coil and injector wires go from plug all the way to ecu, would need to repin there, which is doable, but a complete PITA.... Did more 'stuff' tonight, but no progress... pulled intake manifold off to make sure there was no leak at gasket/seals... replaced the valve seals on those cylinders just to be 'sure' it wasn't valve seal leak had my pals at Cincy Speed do a leak down to confirm my numbers... they did, leakdown was normal before that I also put a borescope in the spark plug hole to see if oil had built up and was puddling on the piston (i.e. bad rings leaving oil in cylinder and puddling in chamber) Quote Link to comment Share on other sites More sharing options...
gillbot Posted May 31, 2013 Report Share Posted May 31, 2013 PITA as opposed to what? Living with an undiagnosed problem? Quote Link to comment Share on other sites More sharing options...
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