Help With 84 Model 302 w/ CFI Setup? Wont Idle (Video) - Ford Mustang Forum

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post #1 of 7 (permalink) Old 06-28-2010 Thread Starter
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Help With 84 Model 302 w/ CFI Setup? Wont Idle (Video)

Hey hows it going, im a new member here with an 84 LTD 5.0 CFI, has been a good car to start and i love it but right recently i had to replace the fuel pump and am having new problems now. I cant find any good ford guys locally that know anything about the CFI setup, and the motor only has 37k on it (estate auction old lady car, have all reciepts for work done). It breaks my heart that the motor is in such good shape but i cant get the fuel delivery right. I know there was 2-3 years of mustangs that had the CFI w/ AOD trans 302 setup, so hopefully you guys can chime in

Heres the story :

I bought the car after having sat for years, seemed to run good for what it was, knowing it needed new gas i drove to the gas station and put 5 gallons in it, the fuel meter said low when i bought it so i figured itd be good to just run what little bit i thought was in it out of it. Come to find out the sending unit was bad, it still had gas in the tank (around 10 gallons i siphoned out when i put a new pump in) and i had only put 5 gallons in it plus drove it around 200 miles. This tells me it had probably 10-15 gallons of 5+ year old gas in it when i got it.

So i replace the fuel pump, put 5 gallons of fresh gas + b12 fuel system cleaner in it and crank er up. First it doesnt run due to air in the fuel lines i suspect, but shortly after bleeding the lines/holding it at an idle it runs fine for the most part, still sputters a little while driving though. Here comes the new problem.

When i start the car, it will idle for approxomately 2 seconds, then shut off, not getting enough fuel to run. Almost like the computer is saying "youve got too much fuel, cut it out." because if i spray ethanol in it it will idle smooth as hell.

The weird thing is, if i hold the gas for 10 seconds to hold the motor over 1000rpm or so, it all of a sudden smooths out. Then it will idle down and run like normal, still with the occasional sputter though.

I wonder if i may have a simple vac leak? But if so why would it smooth out after 10-15 seconds of holding the throttle? I should note that before i replaced the fuel pump i replaced the regulator and intake gasket, but its torqued down good so i dont think its leaking. When i turn the car off, and try to restart it even after it has been running good, the same problem comes back.

Clogged cats maybe? Bad gas clogs cats doesnt it? It doesnt have a muffler ATM, just straight exits out the cats and it was quiet as a new car before i sprayed water into the cats. I have been warming up the cats and spraying water in them to remove some carbon and the overall driving of the car has gotten a TON better, revs better and has alot more power. (Mechanic told me to try this, does it actually work?)

It runs like a sewing machine over 1000rpm, just cant get it to start right. I can see the little vaccum thing that kicks the idle up kicks it up briefly at startup, then immediatly kicks back down, if you hold the idle where it should be it will run, but rough until you hold it long enough for the right amount of fuel to "kick in".

New parts :

Fuel pump
Fuel lines
Fuel filter
Fuel regulator
Intake gasket
Air charge sensor
Oil pressure sending unit
Throttle position sensor
Temperature sensor
Spark plugs (autolite platinum)
Wire set
Dist button & cap
Battery & cables

Im confused as what to do, hopefully someone knows about the CFI deal as im thinking about swapping over to carb or either pulling the motor and putting it in my '66.

YouTube - 84 LTD idle/cranking problem

PS: while the idle is surging like that, i watch the idle control vaccum thing actually push it up and down. Vaccum issue somewhere maybe? But then it sometimes smooths out and runs perfect after forcing it to idle for 10 seconds. The idle is set correctly, idles fine when whatever the problem is stops happening.


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post #2 of 7 (permalink) Old 06-28-2010
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i would try running some profesional fuel injector cleaner thru it, take it to a shop if you dont have the tools, and have them run something like the bg fuel system cleaner thru it, being that you ran it with old gas theres a chance the injectors have some gunk and stick open a bit and the computer dosnt have time to compensate of the extra fuel at start up, my dads 85 stang has the same set up and that cured this problem on his car.

ps. if you bring it to a shop make sure they have the right tools to put the cleaner thru the fuel lines, if not they will just spray the stuff into the intake, good to clean intake but dosnt do a thing for the injectors

good luck with it.

1993 lx hatch, 5 speed, all stock except american muscle cai, flowmaster mufflers, hids and a pro 5.0 shifter, more to come soon.
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post #3 of 7 (permalink) Old 06-28-2010 Thread Starter
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I pulled the injectors out and cleaned the screens and had them flow tested/pressure cleaned at a performance shop. Its a very intermittent problem, which makes me think its some type of sensor.

Also, its running lean instead of rich, you may have misread that
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post #4 of 7 (permalink) Old 06-28-2010
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Which of the two fuel pumps did you replace? The high-pressure pump mounted outside of the tank or the low-pressure pump inside the tank?

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post #5 of 7 (permalink) Old 06-28-2010 Thread Starter
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This one has only one high pressure pump in the tank according to the research ive done. My fuel pressure is on par now at the fuel rail, just not getting it through the injectors on startup
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post #6 of 7 (permalink) Old 06-28-2010 Thread Starter
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I shouldve mentioned its not the fox LTD, its the panther chassis crown victoria ltd. May have confused you guys there.
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post #7 of 7 (permalink) Old 06-29-2010 Thread Starter
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Im gonna go buy a throttle body rebuild today and replace all the gaskets and orings in the throttle body and clean the injectors again and see if that can do anything for me. Anyone else think i should try anything?
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