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Another Mustang Injector Question

B

Better_than_Tom

NAXJA Forum User
Location
Corona
So I searched and searched and could not find the answer so I apologize if its a repeat.

I changed my spark plugs last night and gapped them to .035 and now it runs like crap and CEL is on. I used the same brand and model number Champion plugs. I noticed the old ones were gapped much bigger. My question is my motor has mustang injectors installed in it so do I need a larger gap to compensate for this?

The code I got was P1391 after just changing the plugs. I realize its a code for Cam or Crank sensor but I just think that its too coincidental. Thanks for any help.
 
You sure you got your wires back in the right order? It's easy to mix em up. I had 5 and 6 crossed once. It was driveable, but noticeably rough.

Not sure how that might throw codes.
 
You don't need to re gap because of the mustang injectors.
You adjust gap based on conductivity of the plugs & voltage of the ignition system. Not as a variable with the injector spray pattern.
Look close at everything in the area that you might have touched, bumped or wrestled with. You might find a messed up wire or connector.
I'm betting that your engine is running messed up because the cam or crank sensor signal is off.
 
PS: The old ones probably weren't gapped larger, they were more likely just worn out.
 
Ok so I talked with a buddy on mine and he said to gap them to .054 as thats what a 5.0 is spec'd at and thats what the injectors are from. I did that and the car went from not being driveable to running perfect...Im confused as to why this worked..anyone have any thoughts on long term affects of this?
 
I don't think the spark plug gap was the issue. You probably had a poor connection on one of the spark plug boots that was corrected when you removed the plugs and reinstalled them.
 
I'm pretty sure it wasn't the connection because I changed the plugs 3 times
In the last 2 days tryin to resolve this issue and nothing worked until I did the larger gap. I work on cars alot but I am by no means a motor expert
I mainly due suspension work and fabricating. I am just concerned about reliability on the trails later on if I can't pin point what went wrong.
 
Well, where did my certainty go?
I'll be damned. I've never heard of anyone re gapping based on injectors and still don't see why you would.. but if you're sure nothing else changed incidentally...
Armchair diagnostic, here, but perhaps the crank signal was being thrown because it was running rough enough that the computer saw something wrong but didn't diagnose a misfire?

What you described sounded much more like a misfire than a tuning-for-mods issue... I still don't see why it should have misfired at an 035 gap.

You're positive that every other connection, bolt, etc was the same both times?
 
yossarian19 said:
Armchair diagnostic, here, but perhaps the crank signal was being thrown because it was running rough enough that the computer saw something wrong but didn't diagnose a misfire?

You're positive that every other connection, bolt, etc was the same both times?
Click to expand...

Thats what I was thinking too...that the rough running was causing the crank signal to be thrown. Im not a car mechanic but I work on industrial machinery for a living so I more than know my way around a wrench so Im sure everything else was the same. It doesnt make sense I know but the car is running great now so I guess Ill just keep the gap where is it. The motor was rebuilt by a machine shop about 30k ago so Im not sure if that makes any difference?
 
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