Back fire on start stock 496HO
08-18-2018 | 01:28 PM
#11
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From: Ft. Worth TX
Post 8 have no idea what happened. fixed now here
describe runs fine after start up ? can you reach full rpms at WOT ? 5000 rpms HO mag and 4800 for mag 496 is WOT
I would not rule out CRANK SENSOR here either for starting issues. That signal and cam sensor have to sync for start up among other things
FIXED from earlier mishap
describe runs fine after start up ? can you reach full rpms at WOT ? 5000 rpms HO mag and 4800 for mag 496 is WOT
I would not rule out CRANK SENSOR here either for starting issues. That signal and cam sensor have to sync for start up among other things
FIXED from earlier mishap
Last edited by BUP; 08-18-2018 at 01:37 PM.
08-18-2018 | 01:35 PM
#12
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Joined: Jul 2011
Posts: 9,594
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From: Ft. Worth TX
Even without a real fault code I would not over look the crank sensor. They become an issue even for a hard start for a mild issue to even 300 lost rpms for a medium issue to a complete stalled engine to a no restart and no tach signal for the worst ends of a completely failed crank sensor.
BLEED down fuel pressure - I would really look at the issues here. and what is fuel pressure while the engine is running ?
Last edited by BUP; 08-18-2018 at 01:45 PM.
08-19-2018 | 09:20 AM
#15
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Joined: Jun 2013
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From: Marco Island, FL
Oh just wait, Major leak in the bellows on that engine found when drifting awaiting sea tow. Leak in drive motor lines. Super tight shift cables. And I just had my shoulder joint completely replaced. Life’s great, Boating’s Great.
08-19-2018 | 10:00 AM
#17
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From: Ft. Worth TX
sequential injector firing with 8 coils near plugs. DIS
early coils gen 1 were prone to fail here and there.
gen 1 crank sensor more prone to fail than the later version without the ribs. And the rib crank sensor ( early version ) can even break when pulling it out. Not common but can happen
crank and cam sensor signals are very important
2 versions digital throttle n shift and mechanical throttle n shift.
early years 10 pin wiring harness later years 14 pin wiring harness
IAC can play a role for stalling as well.
more than half IAC failures come from lack of proper maintenance.
More than half PCM repair that I see have a bad IAC circuit. ( H bridge) for PCM 555 and ECM 555
early coils gen 1 were prone to fail here and there.
gen 1 crank sensor more prone to fail than the later version without the ribs. And the rib crank sensor ( early version ) can even break when pulling it out. Not common but can happen
crank and cam sensor signals are very important
2 versions digital throttle n shift and mechanical throttle n shift.
early years 10 pin wiring harness later years 14 pin wiring harness
IAC can play a role for stalling as well.
more than half IAC failures come from lack of proper maintenance.
More than half PCM repair that I see have a bad IAC circuit. ( H bridge) for PCM 555 and ECM 555
08-20-2018 | 08:06 AM
#18
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Joined: Apr 2013
Posts: 309
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From: Lagrange ky
are you sure the coil harness is on correctly. my buddy put his on wrong one time and had the same issue it sounds like your having. it would run just a touch rough and afterfire out the exhaust while idleing.
08-20-2018 | 01:16 PM
#20
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From: Dadeville Alabama
We have had this come through the shop before and kept getting a cam sensor fault. Throw a sensor at it and problem disappeared for awhile but always returned. Changed crank sensor 3 years ago and no more issues. Seems the computer cant tell where engine phasing is so it will constantly throw a cam sensor fault if the two dont match up. Good luck!!
