I've recently been having an issue with my car on WOT pulls, from about 3500-5000 rpms with 85% throttle-WOT the car seems like it misses, the exhaust makes a extrememly distinct popping sound and the car bucks along with the sound. After is pops about 3-4 times it gets back on its feet up to close to 6k then will do the same in the next gear. I cleaned my MAF sensor and checked my o2's. The car has right around 150k miles now, I bought the car almost a year ago with just under 145k, at that time all it had was a K&N filter and Magnaflow catback, since then I've added all the mods in my sig and installed them all myself. It just started doing this about 2 weeks ago out of no where. I'm thinking maybe a bad coil or injector?

 

Is it throwing any codes?

 

Nope no codes.

 

Typically, rough running or misfires with no codes suggests ignition issues - coils, spark plug wires, or spark plugs. There can be fuel related issues, but those usually will throw a code, such as a lean code, when an injector fails or a clogged fuel filter restricts fuel under full, or almost full, throttle conditions. O2 sensor problems also tend to throw a code.

The spark plug condition can be checked by pulling 2 or 3 of them. The spark plug wires can be checked using an ohm meter - they should resistance somewhere between 397 and 1,484 ohms. You can do a visual check for leaking wires by observing the engine running in the dark.

 

Yeah the plugs themselves I replaced when I installed the headers, they have about 4500 miles on them, the wires themselves look good with no cuts or anything. I just have no way of measuring the output, if I wanted to check the coil output though how exactly would I do that, check the actual coil or the plug wire?

 

Coil testing:

https://ls1tech.com/forums/12134938-post12.html


Did you re-oil that K&N anytime recently?

 

Yessir I oiled it about 1k miles ago. And I guess I'll find me an ohmmeter and check things out.

 

Oiled filters are notorious for oil fouling the MAF sensor wires, particularly following re-oiling. If this is part of the problem, it can be remedied by cleaning the thin sensor wires with CRC brand MAF cleaner. (I specify a brand only because some brands, as well as other chemicals can ruin those MAF wires.)

 

I'm pretty sure that's the exact brand cleaner I used 4 days ago when I cleaned the MAF ha, nonetheless problem still persists. The only thing that's weird to me is that my mom had a coil go bad on her Lincoln Navigator and it ran bad all the way through the rpm range, actually even worse at idle. My car starts and idles perfect and runs fine 3k and down, only has the missing problem during high rpm. So I guess IF it is a coil it's just now starting to go bad, not all the way gone.

 

Simple things:

Maske sure NONE of the spark plug wires are touching ANY part of the metal exhaust manifold piping.....that wikll cause mid-upper rpm misfires.

Cracked spark plug will too.

Also, I'd scan the engine while its idling to see if the 02 sensors are switching properly....they will not always throw a code till they get really really bad and/or fail completely.

A bad coil will cause issues at all rpm's....generally.

 

I know one of the wires is pretty close to the primary of the header, I think on cyl #3 or 5, but not touching. All the others have pretty good clearance but I'll go take a look at that, thanks!

 

Have you figured it out?

 

Mine just started doing this last week. Granted I have been running open headers every or every other weekend and haven't turned off the codes. It had been running fine up until we took the Y-pipe off again last week. I'm figuring it's more than likely the cold, running real rich and fouled plugs, or I ruined my O2 sensors. I guess I'll find out next weekend when I have the time and daylight to dick around. Any ideas?

 

It only does it at WoT, it has no uneasy idling, no strange idling noises, no suction at exhaust pipes. It drives 100% fine until it is planted to the floor, then it pops and backfires pretty badly but doesn't seem to suffer any powerloss. I don't think it has anything to do with my valvetrain, as it would be strange throughout the entire course of idling and driving at all rpm's right?

I am trying to get the SES's from doing the LT's tuned out tomorrow, will give an update on it when it is done. Any input or ideas/experiences would be great.

 

Turns out I burned out my O2 sensors. Thanks for all of the help guys... Not!