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Discussion Starter · #1 ·
I just finished adding the MSD coil, wires, cap and rotor and now my engine seems like it is idling rough. Any ideas?.....
 

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Discussion Starter · #3 ·
How do I tell where #1 is on the MSD cap? I tried to copy the motorcraft cap that was on there and I went by the diagram on the engine but if I was off to begin with, then it was wrong. I drove it around the neighborhood and it is definitely not running right. Mine is also a 94 302 XLT
 

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Look in steve83's supermotor page for routing of the wires.

Make sure the wires are push down on to the plugs until they click. Check the plugs to make you didn't crack one bolting it in. I cracked one before and didn't know till the truck ran really rough and back fired.
 

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Driving Stuff Henry Built
-90 xlt, 351w, e4od, man 1356, 3.55, sag, warn hubs, 35s. -73, 400, np435, d20j twin, 35s
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It really doesn't matter where the #1 mark is on the cap, it matters where the rotor is pointing when #1 is at TDC (Before the power stroke). It should point approximately at the wire for #1.

With the key off, turn the engine over with a breaker bar & line up the timing marks at TDC. See where the rotor points. It should point close to your #1 wire. If it's opposite of your #1 wire, rotate the engine 1 full turn & line the marks up & check again. If it's off by 1 position or so, move the wires to correct it.

Like Wayne & Need4 said, recheck the firing order & all. It's easy to have wires crossed up, use the wrong order, run the order backwards around the cap (Probably wouldn't run at all), have a loose connection at a spark plug or two, etc..
 

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Satyr of the Midwest
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It will matter because there is a signature PIP signal for the #1 cylinder.
 

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Driving Stuff Henry Built
-90 xlt, 351w, e4od, man 1356, 3.55, sag, warn hubs, 35s. -73, 400, np435, d20j twin, 35s
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It will matter because there is a signature PIP signal for the #1 cylinder.
:doh0715: More stuff that used to be right, that has changed. Sorry 'bout that, listen to SigEpBlue, he knows more about these ignitions than I do. Although, if you haven't removed the distributor, it seems like the routine I gave would locate the correct position for #1 even if the cap isn't marked.

Where is the PIP signal picked up from? What does it do? If your distributor is installed with the rotor at the wrong position, does it make it so that if you move the wires over 1 position to match, it won't read correctly?
 

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Satyr of the Midwest
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The PIP is generated by a rotor vane cup with a square wave cut into it, sort of.

This capture is by tmoss; pay attention to the upper right corner where it says #1 Shutter PIP:


That shorter signal is the only way the PCM knows where the crankshaft is, rotationally. That's important information so it can calculate when to fire the injectors; whether batch or sequential firing, this is required (even though some Ford literature states otherwise).
 

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It sounds like you missed routed a wire, check that first, I just went thru this with my new 302 EFI motor last week, certainly check your Haynes for firing order in the book.

The MSD cap does not have the #1 lead marked on it but it has a slot on it's bottom that matches the dissy housing nub so the cap only goes on one way, #1 lead on the cap is at 1 o'clock (Haynes) YOU have to mark it so. Go back now and check your wire routing is correct, match the book..................

When I put my dissy back in I needed to rotate the shaft CCW and point the rotor at 1 o'clock, once the rotor is in the correct position mark the inside of the dissy housing for reference and make another mark on the dissy and FI plenum as an additional reference mark should you ever pull the dissy out.

When setting a dissy back in it wants to turn CCW first and then CC this is due in fact to the WIDTH of the cam gear and dissy gear coming together so when it's all the way in you may have to lift and turn it so it winds up in the exact position it needs to be to start.

This assumes you have the dissy out and turned the motor over and don't know what the position of the # 1 piston is at this point.

Pull out the number one spark plug, hand crank the motor with a torque wrench, thumb over the #1 hole until you feel a good push of air so the #1 pistion is at the top of it's stroke, set the Harmonic Balancer to 0 with the timing mark, you should only have to move the HB a little to get to 0, put the dissy partialy in so it goes over the oil pump shaft just wiggle L/R a bit for feel then rotate the rotor on the shaft CCW around to 1 o'clock same as #1 lead on the cap, put the dissy all the way in/down and tighten it.

This is exactly what I did as suggested by my engine builder and it fired up first turn of the key.

Good Luck ~
 

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Driving Stuff Henry Built
-90 xlt, 351w, e4od, man 1356, 3.55, sag, warn hubs, 35s. -73, 400, np435, d20j twin, 35s
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[Hijack on]
OK, so it uses the PIP signal to time the injectors, & they would be firing at the wrong times related to the crank position if the spark plug wires were installed rotated 1 position off. From the distributor's position it would think #1 is firing 1/8 of a turn from where it actually is. I think I get it. Thanks :thumbup
[Hijack off]
 

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How do I tell where #1 is on the MSD cap? I tried to copy the motorcraft cap that was on there and I went by the diagram on the engine but if I was off to begin with, then it was wrong. I drove it around the neighborhood and it is definitely not running right. Mine is also a 94 302 XLT
You probably have your wires mix mached. My MSD cap was marked.
 

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Discussion Starter · #12 ·
Thanks for all the help guys!! I had the wires all out of order. DOH!!!! Got 'em fixed and it's running like a raped ape....Hopefully will get the timing bump next week and will start measuring the results.....WOOHOOO!!!!!!!
 
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