Cylinder Missfire
Thread Starter
Joined: Feb 2005
Posts: 26
From:
Cylinder Missfire
I recently threw an engine code saying that I was having a missfire in cylinder 4 on my 99 GT. I went in and replaced all my spark plugs and decided to change the coil packs betweek cylinders 3 and 4. The problem is still occuring but feels slightly different, it could be that the missfire has switched to cylinder 3 but is throwing the engine balance off differently than when the missfire was in cylinder 4. I got it to throw another code but haven't checked it yet. Could it be the coil pack? What is the life on them? Any info on this would be greatly appreciated. Thanks!
Gentleman's Relish
Joined: Feb 2005
Posts: 13,189
From: AZ
RE: Cylinder Missfire
Worst thing you can do is go in and throw parts (money) at a problem like that without further investigating. Since you've already taken the time and effort to replace the plugs and coil packs of the offending cylinder(s), it could be fuel related (injector) or perhaps a wire going to the pack is bad. I don't have a GT so I've never bothered to check how to test the coil packs incoming voltage but that's a good start. Also, you may want to run a fuel system cleaner through your gas to help clear out any junk in the lines or injectors. You could also test the Injector itself. They sell the injector test lights at auto parts for like 15 bucks and it will show you if the injector is not firing properly or weak.
4th Gear Member
Joined: Jul 2004
Posts: 1,133
From:
RE: Cylinder Missfire
Can you feel your engine misfiring? I pulled a misfire one time and since the o2's werent getting dirty I figured the injector was jacked up and thats what it was. I didnt even feel the misfire when that was happening and running on 7 cylinders....weird.
3rd Gear Member
Joined: Apr 2005
Posts: 607
RE: Cylinder Missfire
What a bunch of misinformation! Why don't some of you do your homework before you spout of nonsense.
He has a 99 GT which does not have wires, and an O2 Sensor will not cause a misfire.
Cylinder # 4 is the passenger side plug all the way in the back closest to the fire wall. # 4 and # 8 are the first ones to go because of the higher heat temperatures in the rear of the engine bay. Luckily they are easy on the Mustang...try reaching those plugs on any F150 or Expedition.
Please explain how you replaced the coil BETWEEN 3 and 4. Each spark plug has its own coil. The cylinder numbering order is whacky on the Fords, you may have replaced the wrong one. Any improvement you noticed is from having a new spark plug in there. Check the codes again and see what you've got.
General rule of thumb:
Coil packs usually act up at low RPMs under a load (usually around 1200-2000rpm). Injectors act up under heavy throttle at higher RPMs. You could putt around town all day and never know you had a bad injector.
He has a 99 GT which does not have wires, and an O2 Sensor will not cause a misfire.
Cylinder # 4 is the passenger side plug all the way in the back closest to the fire wall. # 4 and # 8 are the first ones to go because of the higher heat temperatures in the rear of the engine bay. Luckily they are easy on the Mustang...try reaching those plugs on any F150 or Expedition.
Please explain how you replaced the coil BETWEEN 3 and 4. Each spark plug has its own coil. The cylinder numbering order is whacky on the Fords, you may have replaced the wrong one. Any improvement you noticed is from having a new spark plug in there. Check the codes again and see what you've got.
General rule of thumb:
Coil packs usually act up at low RPMs under a load (usually around 1200-2000rpm). Injectors act up under heavy throttle at higher RPMs. You could putt around town all day and never know you had a bad injector.
5th Gear Member
Joined: Jul 2005
Posts: 2,387
From: Georgia
RE: Cylinder Missfire
Okay, here we go....
One, they do not have 'spark plug' wires in a traditional sense, but they have wires none the less. As such, they are subject to degradation by under-hood heat, which leads into one of your hypotheses.
Two, the crankshaft position sensor WILL cause misfires, but those misfires will remain on that cylinder. AND, it can happen at sustained rpms ABOVE 2400.
Three, we didn't add the bit about injectors, but since a previous post addressed it, why reiterate it?
Four, my first (of many) mustang was built before most folks on the forum were born, so save me the recriminations.
Five - Not one person claimed to be an expert here. We are all here to offer ideas and opinions to assist others, based mostly from personal experiences. AND not one person made suggestions which would cause him to suffer engine damage or incur further expense. To wit, I asked for a list of modifications and which ones, if any, may have been performed recently.
One, they do not have 'spark plug' wires in a traditional sense, but they have wires none the less. As such, they are subject to degradation by under-hood heat, which leads into one of your hypotheses.
Two, the crankshaft position sensor WILL cause misfires, but those misfires will remain on that cylinder. AND, it can happen at sustained rpms ABOVE 2400.
Three, we didn't add the bit about injectors, but since a previous post addressed it, why reiterate it?
Four, my first (of many) mustang was built before most folks on the forum were born, so save me the recriminations.
Five - Not one person claimed to be an expert here. We are all here to offer ideas and opinions to assist others, based mostly from personal experiences. AND not one person made suggestions which would cause him to suffer engine damage or incur further expense. To wit, I asked for a list of modifications and which ones, if any, may have been performed recently.
2nd Gear Member
Joined: Jun 2005
Posts: 164
From:
RE: Cylinder Missfire
Anyways..
When you replaced the coil packs did you replace the boots on them aswell. I have a 99gt, and I have had a couple problems with the boots themselves, not the coils (yet)... Yeah, I have never heard about the stock "wires" ever having a problem, unless there was an engine bay fire, or something drastic happened. If you haven't switched the boots, and just the coils, try that. When mine was misfiring it was pretty ruff, even being just one cylinder.
When you replaced the coil packs did you replace the boots on them aswell. I have a 99gt, and I have had a couple problems with the boots themselves, not the coils (yet)... Yeah, I have never heard about the stock "wires" ever having a problem, unless there was an engine bay fire, or something drastic happened. If you haven't switched the boots, and just the coils, try that. When mine was misfiring it was pretty ruff, even being just one cylinder.
3rd Gear Member
Joined: Apr 2005
Posts: 607
RE: Cylinder Missfire
ORIGINAL: 04BlueGT
Okay, here we go....
One, they do not have 'spark plug' wires in a traditional sense, but they have wires none the less. As such, they are subject to degradation by under-hood heat, which leads into one of your hypotheses. Never seen 16g wire "degradate" by heat...but if you insist.
Two, the crankshaft position sensor WILL cause misfires, but those misfires will remain on that cylinder. AND, it can happen at sustained rpms ABOVE 2400. I never argued that a CPS would cause a misfire, reread my first reply.[/b]
Three, we didn't add the bit about injectors, but since a previous post addressed it, why reiterate it?
Four, my first (of many) mustang was built before most folks on the forum were born, so save me the recriminations. Congrats...[/b]
Five - Not one person claimed to be an expert here. We are all here to offer ideas and opinions to assist others, based mostly from personal experiences. AND not one person made suggestions which would cause him to suffer engine damage or incur further expense. To wit, I asked for a list of modifications and which ones, if any, may have been performed recently.
Okay, here we go....
One, they do not have 'spark plug' wires in a traditional sense, but they have wires none the less. As such, they are subject to degradation by under-hood heat, which leads into one of your hypotheses. Never seen 16g wire "degradate" by heat...but if you insist.
Two, the crankshaft position sensor WILL cause misfires, but those misfires will remain on that cylinder. AND, it can happen at sustained rpms ABOVE 2400. I never argued that a CPS would cause a misfire, reread my first reply.[/b]
Three, we didn't add the bit about injectors, but since a previous post addressed it, why reiterate it?
Four, my first (of many) mustang was built before most folks on the forum were born, so save me the recriminations. Congrats...[/b]
Five - Not one person claimed to be an expert here. We are all here to offer ideas and opinions to assist others, based mostly from personal experiences. AND not one person made suggestions which would cause him to suffer engine damage or incur further expense. To wit, I asked for a list of modifications and which ones, if any, may have been performed recently.
How many posts do we have to have about gears? Over and over again with the same stuipd replies? How many questions do we have to have about PI intakes with the same freaking answers?
And such wonderful responses! I will tell you what, according to the majority...O2 sensors and a bottle of fuel system cleaner will solve anything.
Thread Starter
Joined: Feb 2005
Posts: 26
From:
RE: Cylinder Missfire
Ok here goes... the only mods I have currently are a bassani X-pipe and a K&N FIPK. I switched the coil packs AND the boots when I did my spark plug replacement. I'm gonna replace the boot to see if that clears things up and if not the coil goes next.