Misfire p0305

[lookout4theyeti]

My car was running just fine friday with a little under half a tank of gas. I was in Toledo and about to head back to cleveland for spring break. Anyways, i fill up my tank with shells premium gasoline. Once i get back into cleveland, i notice a random misfire like symptom (odd acceleration, rough idle). However my SES light would only randomely flash.

Last night I went to autozone and bought new plugs and wires ( i needed new plugs anyways) and swapped those out. (It only took me an hour and a half, not bad compared to how long some people on the board say it takes). That didnt solve my problem. I was down to about a half tank at this point and I had to drive my car. SES light came on and stayed on, so today i took it up to autozone and they scanned it. It came up with a p0305. A misfire on cylinder 5. Hoping that it was just bad gas, i purchased some octane booster and fuel injector cleaner. I put that in and we'll see how it goes and see how it is next time i fill up my tank.

I dont think its the coil because if a coil is shot, isnt it usually a paired misfire rather than just one cylinder misfiring?

Anything else to check for?

[Bonemaro]

Re: Misfire p0305

I had the code a month ago. Car ran like crap. missing 5. I was thinking the same are you; wouldn't it be misfiring on 2 and 5. I did the plugs and wires. NO!!!! I replaced the coil on a hunch and it runs as good as new. I betcha that's your problem.

[lookout4theyeti]

Re: Misfire p0305

I see... just outta curiousity, how much did you pay for the coil?

[Bonemaro]

Re: Misfire p0305

Actually, I got 3 of them on eBay for $5, plus shipping.

[lookout4theyeti]

Re: Misfire p0305

Actually, I got 3 of them on eBay for $5, plus shipping.

wow... great deal lol...

Well I think im gonna go ahead and pull the coil out tomorrow and test its primary and secondary impedance.. I'm assuming if its impedance is higher than it's supposed to be than I know the coil is shot? My haynes manual has the specifications in it.

[Bonemaro]

Re: Misfire p0305

yup yup... let me know.

[lookout4theyeti]

Re: Misfire p0305

This may be a dumb question, but if I change one of the coil packs should I change all 3?

[Bonemaro]

Re: Misfire p0305

if you got the money, but not required. I only did one.

[Hib Halverson]

Re: Misfire p0305

When the service engine light flashes, that's the PCM's OBD2 diagnostics indicating to the driver that whatever is wrong will damage the catylitic converter if the problem persists. Bad misses will flash the light. Not so bad misses will just turn the light on and set a P-code.

The SES will stop flashing and either stay on or go off when the diagnostics "believe" the problem is no longer severe enough to damage the cat.

As you know P0305 is a #5 misfire.

It could be ignition-related and you can throw parts at the problem until you fix it. You also can get the FSM and troubleshoot according to what the book says. If you do that, you'll probably only buy the part that is actually defective.

That said, there are other reasons an engine can miss. For example, burned valves, camshaft lobe failures or other mechanical problems.

[lookout4theyeti]

Re: Misfire p0305

Just wanted to update you guys..

Car is running fine as of tonight. I replaced the coil for the 2/5 cylinders.

I went out today and tested each of the coils by pulling one plug wire off at a time and listening for spark. Didn't get any spark on the 2/5 coil so i pulled it out and tested its resistence. Primary resistance was at about 1.3 when it should be no higher than about .6 (according to my haynes manual). Just to be safe, i took my ignition module up to autozone to have them test it and it checked out fine, so I bought a new coil and replaced it. Car is running good as new. I'll give it a few days to be sure, but I'm hoping that was all of my problem.

Also cleaned my k&n filter while i was working on the rest of my car... man that thing was dirty... i guess 300 freeway miles every other week plus some city driving will do that...