Thanks for the input. I think you're right. Will put this on the to-do list.

 

Good morning guys, this is a lot of GOOD info and a great video, I don’t mean to hack this tread but I got a CEL misfire cyl #2 I unplugged the batt and 30 min later reconnected it and the cel was erased, but this morning when I started the car it idle for about 2 min the car sputter lightly for a sec and the cell came back. any advice?

 

It is what it is....bad coil or bad spark plug #2 cylinder. Replace.

 

What DBJoe996 said.

Without knowing the car's history was anything done to the car recently? I'm thinking that if the plugs/coils were done recently this misfire could be due to an bad connection between the coil and plug or between the coil and the engine harness.

If the plugs/coils have not been done recently and are in fact close to due to be changed based on time or miles just change them all.

If the coils are original and have some miles/age on them you might want to consider changing all of the coils, too.

 

The only thing I did to my car was put a K&N filter and did the airbox mod.

 

Well, that's important.

While the MAF is properly protected from dirt (and oil is not a worry with a dry type filter) and can operate for years and hundreds of thousand of miles with no problems, unfortunately this doesn't always apply when the stock air filter is replaced with an aftermarket air filter that requires oil to bolster its filtering.

Aftermarket air filters that require oil to filter can result in the MAF getting fouled.

And I do not know what air box mod you refer to but the stock air box is designed to ensure the air flow into the intake hose between the air box and the intake manifold is linear so the MAF which sits between the air box and the intake manifold receives linear air flow.

Turbulent air flow at the MAF can cause all sorts of hard to diagnose symptoms.

Thus modifying the stock air box is done at the risk of upsetting the very critical air flow from the air box past/through the MAF and into the intake manifold.

My advice would be to carefully remove and clean the MAF. While I normally do not believe MAF cleaning is necessary, and I certainly do not clean the MAF in either of my cars, in this case I think it called for.

Then to eliminate air flow as a cause I would advise you to return to the stock air filter and air box configuration.

If the misfire goes away then you can consider how much if any of the air filter/mods you want to reapply.

If the misfire doesn't go away come back for further comments/counsel from the forum member.s

 

The K&N filter is dry, Should I replace it with a OEM one?
As far as the Air box mod, I went a head and bought a smooth silicone intake pipe that replaced the OEM accordion intake hose. The I took out the hemholz box and capped it.

According to the Code scanner it was a Cyl 2 misfire. I reset the Cel and it hasn't come back yet.

 

Agreed with Macster about potential side effects on intake mods. If the misfire code is always cyl 2 and cyl 2 only though, it's more likely it's the coil/plug on that cylinder.

 

I installed a scan gauge. Now it will be easier to monitor the cel.

 

Let us know what you find.

 

+1

I'm curious as well. Coils/plugs were just replaced on my car due to a flashing CEL & running rough. Last week, it threw a flashing CEL again while idling at a stoplight on the way to lunch. The light did not come back on when the car was started up after lunch and has stayed off ever since. The weird part is that there were no stored or pending codes when I hooked it up to my scanner.

 

An air filter designed to be oiled that is not properly oiled, in this case has no oil, is not going to do as good a job of filtering the air.

The best air filter for these engines is the stock air filter. A number of cars have obtained a high number of miles with stock filter and are still running just fine. If the air filter was not any good these engines would not have reached the miles they did. Additionally there are a number of UOA results posted and I have yet to see one with high silicon numbers, silicon being a sign dirt is making past the filter into the engine.

Whether you want to replace the aftermarket filter with the stock one is up to you.

What you can do, what it appears you are going to do, is just drive the car and see if the misfire code comes back. If it doesn't... think about if you keep the aftermarket air filter in service properly treating it with oil so the filter delivers its optimum filtering and protects the engine.

If the misfire comes back, I would advise you check the plug's installation -- is it possibly loose? -- and the coil's installation -- is it securely connectted to the plug and it is securely and properly connected to the engine wiring harness? to make sure the misfire doesn't have a simple explanation.

If you can find no apparent explanation for the misfire, swapping coils is a technique to determine if the new coil is possibly defective.

(The other day I had my Boxster's plugs changed. The coils were found to be ok. The tech however tossed in along with the old plugs a new coil that was bad. It seems these new coils have some electronics in the coil that can increase some the likelihood the coil can suffer from premature failure as these electronics are a weak spot.)

If the misfire follows the coil well, there you are.

If it doesn't then the plug has to be suspect.

In the case the plug is suspect, I would not swap plugs. I treat plugs as an install once item. I would just replace the suspected bad plug with a new plug.

If the misfire remains then it could be the air box -- the #2 cylinder just being the most sensitive cylinder (granted a bit of a stretch) -- but it could be something else.

Going back to the stock air filter and air box would be preferable to diving into an engine teardown.

If the misfire remains after all the above them come back for further discussion.

 

That is not weird just the way things work.

In many cases if the CEL triggering condition goes away the CEL is turned off and the associated code is erased.

In some cases while the code is no longer active, and there is no pending code, there is a permanent code. Permanent in that the code can only be erased if the DME fins the triggering condition absent over a number of engine starts/warm up cycles.

 

Thanks for chiming in. I was a bit surprised to find no stored codes. For troubleshooting purposes, it would be nice to know which cylinder(s) were misfiring. The scanner is in the car, so I'll be ready next time. This, of course, guarantees that it won't happen again.

 

Ok so far the Cel hasnt come back, And of course now that I have install a "scan gauge"