575sci spitting back
I am experiencing spitting back thru the throttle bodies once the motor is thoroughly warm. This happens randomly at all load positions except idle. I am running an msd ignition and have tried with the box out of circuit and the problem remains.
Any ideas anyone? |
Do you mean backfiring, popping through the throttle body???
If so, it could be a cam lobe, broke valve spring or in the ignition. |
As Griff said, sounds like it's in the valvetrain. Check the cam lobes really good. It's a flat tappet cam and they have been known to flatten a lobe. You can put a dial indicator on the rockers and check the total valve lift. Should be .530 on the intake and .551 on the exhaust.
Also check for a broken spring(s). Eddie |
Originally Posted by Young Performance
(Post 3476428)
As Griff said, sounds like it's in the valvetrain. Check the cam lobes really good. It's a flat tappet cam and they have been known to flatten a lobe. You can put a dial indicator on the rockers and check the total valve lift. Should be .530 on the intake and .551 on the exhaust.
Also check for a broken spring(s). Eddie |
Originally Posted by mossfred
(Post 3476434)
Thank you for the suggestions, my thoughts too except why no popping while it's warming up?
at it, and on these engines, they tend to throw alot at them. That might be masking other issues. |
Fixx
throttle bodies will fart and pop when you have low fuel pressure..check the fuel pressure first,,will be OK when cold but as it warms up it will pop and fart from low pressure..
|
Originally Posted by mrfixxall
(Post 3476605)
throttle bodies will fart and pop when you have low fuel pressure..check the fuel pressure first,,will be OK when cold but as it warms up it will pop and fart from low pressure..
This is quite tricky for me as here in Europe no one has any experience with these motors and as soon as i mention 575SCI everyone runs away!! I forgot to mention these motors have the ASM pulley and ecm re-progamme and they dont run rich. I am thinking electrical still, maybe the magnetic pickup in the dizzy, cracked cap, even the coil, perhaps because these are easiest to fix!! |
Fixx
Originally Posted by mossfred
(Post 3476884)
If i can rely on my fuel pressure guages, the fuel pressure is normal.
This is quite tricky for me as here in Europe no one has any experience with these motors and as soon as i mention 575SCI everyone runs away!! I forgot to mention these motors have the ASM pulley and ecm re-progamme and they dont run rich. I am thinking electrical still, maybe the magnetic pickup in the dizzy, cracked cap, even the coil, perhaps because these are easiest to fix!! |
If it spits at you spit back!
|
Originally Posted by mrfixxall
(Post 3477273)
ok? what is your normal fuel pressure?
One injector on each throttle body was not firing. I decided to check if switching the wires on the injectors would move the problem to that injector but......as soon as i tried that they all started working!! Now the motor runs perfectly, but i do not know why the injectors stopped or why they work again. That is the real question???? |
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