miss firing

[My1stBronco]

i have a 1992 bronco with a 302 in it and i changed the wires and its miss firing really bad. the engine is also shaking the car really bad at idle. its also making a poping sound a lot. any ideas?

[BroncoRN]

did u put wires in exactly the same place? also make sure they are all seated on distributor and on the plugs?

[My1stBronco]

yeah i checked the haynes manual for the firing sequence and i put the wires on in the right order. and i checked that everything was on real tight but still nothing. i just bought the truck about two months ago and i just changed the wires. the order the previous owner had them on was different from what the manual said. it has a rebuilt motor in it so im thinking it might be different. i tried them in both the right order and what was previously on there and nothing seems to work.

[BroncoRN]

you might have bad wires. where'd u get them from? take 'em back and see if new ones work better. did u change plugs? or do anything different?

[SigEpBlue]

There's an "older" firing order and a "newer" firing order for the 5.0L engines.

Newer: 1-3-7-2-6-5-4-8
Older: 1-5-4-2-6-3-7-8

Notice the "3-7" and "5-4" are essentially "swapped," and that the distributor rotor rotates counter-clockwise.

Have you pulled the plugs and made sure that they're all in decent shape? You could have a broken plug or one(s) that isn't/aren't firing correctly, dumping fuel into the exhaust system & contributing to the unevenness at idle.

[MrWP819300]

Originally Posted by My1stBronco

yeah i checked the haynes manual for the firing sequence and i put the wires on in the right order. and i checked that everything was on real tight but still nothing. i just bought the truck about two months ago and i just changed the wires. the order the previous owner had them on was different from what the manual said. it has a rebuilt motor in it so im thinking it might be different. i tried them in both the right order and what was previously on there and nothing seems to work.

What order did you use? and what engine was swapped into it? SigEp has it right, will only be one way or the other.

[My1stBronco]

i put new plugs in about a week ago so those are good. i tried both codes sigep said and niether worked. i also pulled the new wires off and put the old ones back on and still nothing. now it wont even turn over. something is seriously messed up now.

[MrWP819300]

Originally Posted by My1stBronco

i put new plugs in about a week ago so those are good. i tried both codes sigep said and niether worked. i also pulled the new wires off and put the old ones back on and still nothing. now it wont even turn over. something is seriously messed up now.

Sounds like it may be something more. But if it ran ok before you changed the wires, then you must have gotten something wrong, like the location of the wires.

[jopes]

if it ran fine before you changed wires now no longer runs. you need to follow the fireing order and install the plugs correctly.

[My1stBronco]

the wires are in in the right order for the firing order so its not that. i got it to start up today but it was running like garbage. i put a new cap and roter in but its flooded now so i pulled the plugs and im gonna let it air out for a while and see if that helps.

[jopes]

Originally Posted by My1stBronco

the wires are in in the right order for the firing order so its not that. i got it to start up today but it was running like garbage. i put a new cap and roter in but its flooded now so i pulled the plugs and im gonna let it air out for a while and see if that helps.

just because it is the right order does nto mean you put them on the cap to the corrisponding cyclinder.


Like I said, from what you have posted it ran fine, you changed the plug wires and it no longer runs. this means the wires are not installed correctly.

[BroncoHector]

Just because the manual shows it that way doesnt make it correct, I have a Haynes, a Chiltons, and the ford CD and one of them is incorrect. so recheck your plugs locations on the cap

[SigEpBlue]

I suppose he could do a very rudimentary check: run a pseudo-compression test with a degree wheel on the crank snout; I say "pseudo-" since he'd not really be checking compression, but he'd at least be able to see in which order the cylinders are on their compression stroke. That way, he can a) ascertain that each cylinder is actually compressing the gases (to some degree at least), and b) he can see where the rotor is pointing on the distributor cap and then relate it to the crankshaft position. Should come out with a right-on firing order, regardless.

[Mr. G]

Originally Posted by SigEpBlue

There's an "older" firing order and a "newer" firing order for the 5.0L engines.

Newer: 1-3-7-2-6-5-4-8
Older: 1-5-4-2-6-3-7-8

...and that the distributor rotor rotates counter-clockwise.

Originally Posted by SigEpBlue

I suppose he could do a very rudimentary check: run a pseudo-compression test with a degree wheel on the crank snout; I say "pseudo-" since he'd not really be checking compression, but he'd at least be able to see in which order the cylinders are on their compression stroke. That way, he can a) ascertain that each cylinder is actually compressing the gases (to some degree at least), and b) he can see where the rotor is pointing on the distributor cap and then relate it to the crankshaft position. Should come out with a right-on firing order, regardless.

I give my Auto Tech students a similar problem every year. Here are the instructions I give them, modified for this situation.

You must keep in mind a few points about any used vehicle when attempting to work on it:

• You have not owned the truck since it was born, therefore you don't know what has been changed before you got it.
• Any work that a non-factory technician has performed may change the way it was put together vs. the way it came from the factory (The way the manual says it should be.)
• Manuals have typos.

Here is the procedure for getting it straightened out: (you may need help, as another pair of hands make this a lot easier, but it can be done solo on an FSB,)

• Remove the #1 spark plug (pass-side front)
  
• Get a long-handled ratchet and socket set up on the crankshaft bolt.
  
• Cover the spark plug hole with a finger and begin rotating the crankshaft clock-wise.
  
• As you begin to feel pressure under your finger, you now know that he #1 cylinder is on the compression stroke, and that hte spark plug will fire just before TDC.
  
• Now look at the timing marks on the crankshaft damper and align the 0/TDC mark with the pointer.
  
• Remove your distributor cap. The rotor should now be pointing at he terminal for #1 cylinder. Mark the cap extension on the outside inline with where the rotor is pointing.
  
• Check to see if the terminal on the cap lines up with this mark. If not, loosen and rotate the distributor a little until a terminal lines up with the rotor. This terminal will be where your #1 spark plug cable goes.
  
• As your 302 SHOULD use the later firing order, start with that order installing the wires counter-clockwise (ccw.)
  
• Reinstall all previously removed components. BE SURE TO REMOVE THE RATCHET FROM THE CRANKSHAFT!!
  
• Start the engine. It should now run fairly smoothly. If not, double check your firing order and direction. It's very easy to mix-up the wires fro the pass-side of the engine due to the intake upper manifold.
  
• If the engine still runs roughly, you may want to try and install the plug wires in the "older" firing order, with #1 starting in the same place and still using the ccw rotation.

Don't forget to set your base-timing after you get it running smoothly.

It is possible that someone installed an "old" firing order camshaft. Since these engines are batch-fire fuel injection, they will still run ok with that cam installed. SEFI would not run well at all, though.

Good luck.

[BroncoHector]

"BE SURE TO REMOVE THE RATCHET FROM THE CRANKSHAFT!!"

LOL good advise, I bet one of your student must have forgotten to do this.

[rooney77]

Kinda like reconnecting the fuel line after setting your timing on an early body style Bronco. Putting out a fire while you're hovering over the motor is exciting.

[MrWP819300]

No update yet?

[My1stBronco]

i did something different to check my number one position for the rotor. i pulled the number one spark plug and put a hanger in the hole and turned the crank shaft till it was at its highest point. then i checked the rotor and it was pointing to the number one position and i have the wires going from the cap to the plugs counter clockwise in the correct order. i also checked the timing and it is right on. so far i have put in new plugs, wires, cap, rotor, coil and it is still firing up really hard and running rough. i cant figure out what the problem is and its driving me crazy.

[MrWP819300]

Number 1 on TDC (Top Dead Center happens twice for each combustion cycle. To make sure #! is at TDC, if you are going to put something inside the cylinder, just put your finger over the spark plug hole and when you feel pressure, then stick your hanger in there to get the top. Then pull your cap. Wherever it is pointing, that is #1. I bet someone in the past stabbed the dizzy in wrong and adjusted the wire locations on the cap to compensate.

[jopes]

Originally Posted by My1stBronco

i did something different to check my number one position for the rotor. i pulled the number one spark plug and put a hanger in the hole and turned the crank shaft till it was at its highest point. then i checked the rotor and it was pointing to the number one position and i have the wires going from the cap to the plugs counter clockwise in the correct order. i also checked the timing and it is right on. so far i have put in new plugs, wires, cap, rotor, coil and it is still firing up really hard and running rough. i cant figure out what the problem is and its driving me crazy.

could you please state weather this was running fine before the plug wires were changed?