uh oh! is that a misfire?

[iLkYsPoNy]

okay, so i figured that jerky feeling and misfire sound in my exhaust was infact a misfire. well, i changed the plugs, wires, cap and rotor. all this was done after i did a fuel injection service ( canister that sprays into the throttle body ). well, i'm still getting an intermitten but still becoming more common, misfire condition. occasionally the check engine lamp will come on but will go back off after 4-5 seconds. this is a completely stock 5.0 except for the complete exhaust package ( headers back ) and the by-passed smog pump. One thing I've noticed, which I'm not sure if it's normal or not, is there is a fuel smell from the back side of the engine near the firewall? Also, under VERY light pedal pressure, the engine has wanted to fall on it's face. Any suggestions?

 

[JChalfan]

okay, so i figured that jerky feeling and misfire sound in my exhaust was infact a misfire. well, i changed the plugs, wires, cap and rotor. all this was done after i did a fuel injection service ( canister that sprays into the throttle body ). well, i'm still getting an intermitten but still becoming more common, misfire condition. occasionally the check engine lamp will come on but will go back off after 4-5 seconds. this is a completely stock 5.0 except for the complete exhaust package ( headers back ) and the by-passed smog pump. One thing I've noticed, which I'm not sure if it's normal or not, is there is a fuel smell from the back side of the engine near the firewall? Also, under VERY light pedal pressure, the engine has wanted to fall on it's face. Any suggestions?

Pull the codes and see what the computer is trying to tell you, then go from there.

The fuel smell isn't normal. The fuel pressure regulator is on the back of the engine by the firewall, take a look at it and see if it's leaking. It's the little cylinder looking thing mounted to the fuel rail, with a vacuum line going into it. It's on the passenger side of the engine, behind the throttle body.

Jeff

 

[04sleeper]

You didn't mention what year it was but if it has a MAF them I would clean the sensor with electrical contact cleaner.

That is assuming all other tune up items are up to par.

The smell of fuel could be a cut line from the gas tank vent tube running to the charcoal canister.

 

[iLkYsPoNy]

1992 mustang gt... sorry.
yes there is MAF on it, would that cause a misfire type condition?
thanks for letting me know about that fuel regulator, i will definetly check that... i dont need a frickin' fire to break out under there! if there were a problem with that canister... say a leak from it or the vacuum line would that cause my condition?

 

[iLkYsPoNy]

something else i forgot to mention that i didnt think would be of concern until i read another post was the fact that my wires are crossed/wrapping/touching each other. i went from what i believe were stock wires to a set of msd super conducters, they dont fit so well in the stock looms and are exceptionally longer than the ones that were on it. same problem still from the old ones to the new ones, but could it be different causes with the same reaction? i literally as of right now has the wires tucked around each other to keep then off the engine. bad idea. i know.


1992 mustang gt 5speed
thanks for telling my about the fuel regulator, i needed to know that. i definetly don't need a fire to break out under there!

 

[04sleeper]

1992 mustang gt... sorry.
yes there is MAF on it, would that cause a misfire type condition?
thanks for letting me know about that fuel regulator, i will definetly check that... i dont need a frickin' fire to break out under there! if there were a problem with that canister... say a leak from it or the vacuum line would that cause my condition?

A dirty MAF element would cause what you are saying.

Check to see if there are any leaking injectors around the intake and fuel rail areas where they connect.

Also you could have a loose injector wire. Make sure they are plugged in all the way.

If there is a probelm with the charcoal canister it would not cause the issue you are talking about. If anything a vacuum leak would give you a high idle. The line running from your gas tank does not have vacuum but could be cut and could cause a gas smell.

As far as plug wires go I like to use zip ties to space out my wires. I put one big zip tie around the set of 4 wires and use smaller ones between them to keep them spaced out. Then I tie them away from the headers either on the brake lines or A/C lines. See Pic.

 

[JChalfan]

I've used zip ties to seperate and route my plug wires too. It's not the best looking solution, but it will work great especially until you find a better solution.

I'm not sure the MAF would cause the missfire, but it could definitely cause the "falls flat on its face at light throttle" condition. It's definitely worth cleaning it and seeing what happens.

04sleeper, I'm jealous of your clean engine compartment.

Jeff