- May 24, 2008
- 8
- 0
- 1
'66 Fastback...stock 302 roller...primarily '89 Mustang EFI components....Crown Vic left hand air intake....external Hypertech HY-4018 fuel pump at tank....T5 trans. Motor was professionally rebuilt and car ran fine until sent out for paint...15 months later the engine has an intermittent low RPM miss/stumble that stops abruptly at about 1500-2000 RPM when accelerating, is most noticeable in 3-5th gear. If the car wasn't EFI, it feels almost like it's stumbling and then the secondaries open up and it runs perfect, then when you shift, it starts all over again. On occassion, it doesn't do it at all.
So far I have:
Removed upper intake and cleaned everything, new Fel-pro gasket
Checked for any external vacuum leaks
Cleaned Idle control motor & throttle body
Cleaned mass air flow sensor
Reset throttle position sensor from 1.3v to .99v as instructed
Base idle re-set procedure
New ignition coil (old unit read low by 1/2)
New fuel filter @ tank (old unit seemed restricted, fuel lines were new metal prior to engine)
Re-lube ignition control module backing
New temp sensor to computer
Check fuel pressure...reads steady 32lb @ idle
More new plugs, wires, cap & rotor
Check computer for codes....none current or stored
Both oxygen sensors....one in each header
Rebuilt Bosch design III injectors 19 lb.
New fuel pressure regulator
I have played with the timing up and down the scale, played with the plug gap up and down....nothing helps. Here is some more component info if anyone really knows this stuff good enough to check compatibility.
Computer: A9S....seems to be a California EEC-IV unit....similar to the A9L
Maff sensor: F1ZF-12B579-AA
MAP sensor: E8EF-12A644-A2A
If anyone has any realistic ideas on what could be wrong with this thing please help me!
Thanks, Dave
So far I have:
Removed upper intake and cleaned everything, new Fel-pro gasket
Checked for any external vacuum leaks
Cleaned Idle control motor & throttle body
Cleaned mass air flow sensor
Reset throttle position sensor from 1.3v to .99v as instructed
Base idle re-set procedure
New ignition coil (old unit read low by 1/2)
New fuel filter @ tank (old unit seemed restricted, fuel lines were new metal prior to engine)
Re-lube ignition control module backing
New temp sensor to computer
Check fuel pressure...reads steady 32lb @ idle
More new plugs, wires, cap & rotor
Check computer for codes....none current or stored
Both oxygen sensors....one in each header
Rebuilt Bosch design III injectors 19 lb.
New fuel pressure regulator
I have played with the timing up and down the scale, played with the plug gap up and down....nothing helps. Here is some more component info if anyone really knows this stuff good enough to check compatibility.
Computer: A9S....seems to be a California EEC-IV unit....similar to the A9L
Maff sensor: F1ZF-12B579-AA
MAP sensor: E8EF-12A644-A2A
If anyone has any realistic ideas on what could be wrong with this thing please help me!
Thanks, Dave