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Hey Guys,
I have a 2006 GTO with a 234/242 .600 lift cam. It idles and runs great. Only issue is it won't start up on first crank at times but will start immediately on 2nd try. Almost like a bad cam sensor but no codes are present. Can anybody help me with what to change in the tuning to help this issue? Thanks,Jerry
Is your fuel pressure good?
As far as I know. Car had no issues until the cam swap.
Post the tune.
Here is the tune. Thanks!
Are you running a dual chain with modified front timing cover? I ran into a guy with this same issue and mine does it as well. It's not in the tune because you can hold the key for 20 seconds and it will fire on the wrong stroke and you'll hear it popping into the exhaust if you do. At any point whether it's 1 second, 10 seconds or 20 seconds during the 1st attempt without have let off the key, cycle key quickly and it will fire immediately on second turn forward. Doesn't happen every time. I suspect something with the dual roller upper timing gear and the cam sensor. I've swapped cam sensors but same issue. I'm considering shimming the sensor out a tad to see if it's too close and not properly detecting the bump on the gear.
Yep, Dual chain. It is doing the same as yours! Thanks.
So this makes you, a buddy of mine in an 06 GTO, the random guy i ran into with an LS2 and mine that all do this. We all run dual timing chains. So I am suspecting an issue with the upper gear since this is what the cam sensor uses to trigger the first firing cylinder on crank. I suspect the sensor is too close to the gear causing a false reading when the raised portion of the gear isn't under the sensor. I will test this by spacing mine out as far as it will go and still detect the raised portion.
I considered that it could be not close enough to it but I don't think this is the case because the stock upper gear is farther away (being a single gear and thinner) and never seems to have an issue on anything I've worked on. If that is the case, I can machine the cover or the sensor (to a degree) to get the sensor closer to the gear. I'll test spacing it out first.
I'm bumping this thread because I ran into 2 other cars this year that has this exact issue. One was another E40 ecu but another was a 411 LS1 style, but he converted his LS2 to a 24 tooth wheel and kept the cam sensor in the front cover. Both guys also had dual timing chains. So I'm convinced this issue is with the dual chains and using a front cover cam sensor as I've seen 3 other cars plus mine plus the OP all with dual timing chains and front cover cam sensors having this issue.
Anyone figure out a solution?
Is it cold start, hot start or both? Try reducing cranking air fuel table by 20% and add 5 grams (from stock value) to the startup table.
Ed M