i have a 99 se-l runs great 2 days ago it starts to miss if i get on and back fire so i changed plugs and thought that would fix it but i still get code p0305 for liss in #5 i check coils they r good plugs are new and gapped right if i draive the car a lil hard it will drive fine but when i really get on it it will miss and back fire i think i might have got some bas gas at mobile i allways use shell but i was on E so i put 15 bucks in of 91 at the mobile and i didnt drive the car for 3 days after that.so if any 1 can help thanx allmost 4got when i get on it hard the engine light will flash

 

I had the exact same issue.... i changed the plugs, twice (first time i put in boshe 4 prongs, then changed em out for NGK's.) i checked all the coils, chaned the fuel filter, put in shell gas after I ran it to E and now it runs fine.... Mine was a very similar thing and it turned out to be bad gas.

 

thats what im thinking i allways put shell put i needed gas and i put the mobile in my check engine light is stuck on now

 

use an octane booster and fill with shell high test if you still see it after the tank, swap coil packs with a different cylinder and check to see if code changes, coil pack can sometimes only fail under load.

 

ok i will try that thanx

 

99's are notorious for bad coils. Even though you measured it, it still may not be firing the plug hot enough, therefore misfiring under heavy loads. Change the coil on #5 and I'm willing to bet your misfire will go away.

Bad gas is more of a myth...

 

NOT REALLY MY FRIEND HAS A 98 AND HE PUT SOME AMPM GAS AND HIS CAR RAN LIKE ****

 

Agree w njmaxseltd re the coil. Bad gas would likely affect all cylinders equally. Swap coils and see if trouble moves.

 

[quote=bobflood;7836604]Agree w njmaxseltd re the coil. Bad gas would likely affect all cylinders equally. Swap coils and see if trouble moves.[/quo

i will after i get code gone than i will swap coils and se if code pope up again and see if it changed

 

Very true. All the gasoline comes from only a few different refineries. The detergent and/or additive package may be different (techron, etc) but the gas is essentially all the same.

 

Just my 2cent. But cars hardly ever missfire from a fuel problem. Usually its the ing.sys or the the dreded mechinal miss i.e bent valve, week valve spring or worse. Is thier any noise to go along with this missfire? O and FYI if the CEL is flashing the owners manual says that contuing to drive with the light flashing will cause imminent/permnent cat-converter damage i.e you will melt the pre-cat on that side of the motor. $$$$ big money repair. Just a frindly warning.

 

Dont wait to clear the code.
Gas would affect all cylinders and If its a bad coil you wont be able to clear it anyway.
Swap coil with an adjacent cylinder, CLEAR CODE MANUALLY, and see If the code moves to the cylinder you swapped to.
If #5 comes back with the same code, a compression check is in order.

I see the code is for a miss, not a bad coil. It could be the injector, swap the coil and go from there.

 

WELL I DROVE THE CAR TO BUT IT WAS ABOUT 35OUT SIDE AND I DIDNT LET THE CAR WARM UP TO MUCH AND I CHECKED FOR CODES AND GOT A CODE FOR MISS IN #1 THIS TIME BUT I DIDNT EVEN SWAP COILS YET THAN I CLEARED CODE AND 2 NITE I STARTED CAR LET IT WAR MUP FOR 15MIN THAN DROVE THE **** OUT OF IT AND NO CODES IT DROVE LIKE IT WAS NEW THING RAN GREAT

 

Probably bad fuel causing random misfires then. Fill up with good stuff and then worry about it.

 

yea i think it got to the shell gas so it started to run better lol who knows but i will have to do some test

 

ive had a 97 98 and 99 and the 99 needed new coils
it would run fine sometimes but always acted up untill i changed them

 

[quote=97maxcades;7838454]ive had a 97 98 and 99 and the 99 needed new coils
it would run fine sometimes but always acted up untill i changed them[/q

car is still going like a dream but i will give it a few more days to see

 

My 95 had been misfiring intermittently for quite a few years. I finally picked up a set of coils from ebay for 90 bucks and all seems fine now. They are from a 99 though, doh!. The "new to me" coils are hanshins so they should be ok. I never did get a coil or misfire code at any time. It would only misfire after everything was well warmed up (about 30 or so miles of driving)
Hopefully yours was just bad gas.

 

[QUOTE=99MAXPIMP;7839828]bought 98 coils no more misfires - my were sensitive to major temp changes it seemed like

 

car is still going good

 

See sig...throw some chevron in that bish

 

This sounds like my car when I first got it...

A. Spark plugs are NGK?
B. Make sure you don't have the 99 coils in there, they're notoriously bad, replace that #5 w/ a 97 coil pack.
C. Has the car been sitting for awhile? If so, some new gas will take care of it.

And one moar tinggg.... Bad gas is not a myth, or my car has a mind of it's own and somehow magically knows when I get gas from shady places.

 

I was told to always try to fill up in the morning, when its colder out as the gas is more dense and you get your money's worth, especially in hot climates during the summer. And never fill up when a tanker truck is filling the Gas Stations underground tanks as it stirs the dirt settled at the bottom of the tanks and will end up in your car.

 

Those gas tanks are pretty deep underground, I would think the climate outside would have a very minor effect on them...

As for the gas trucks stirring up the tanks? that could explain my last tank of bad gas (or for the fact that I got it from Kroger's).

When I installed my catback I filled up at Kroger's (had the 10c discount wooot), and that tank of gas was miserable, i was attributing the misfires to my catback but low and behold I goto the brand new gas station that opened within a month ago, misfires are all gone and the car is running great!!

Long story short I no longer just stop at any cheap gas station, I stick to my 3 texaco's (whichever is the cheapest), the car likes it, my wallet likes it, win-win....

So ya to the OP, make sure your gas is on point (good)! Start paying attention to how the car behaves after certain large purchases of gas from certain stations.

 

car is still running good i thin kit was the ****ty mobile gas and thats y i use shell vpower

 

no doubt man.

I only go to one gas station and I NEVER put mobil in my car.

 

I believe there's such a thing as bad gas too! I've never used Shell. Why are they so good? I try to go to BP here in Minnesota because they're the only ones that have 93 octane. Otherwise I try to use Super America - 92 octane. My car's runnin' bad right now. Wife put in Kwik Trip 91 octane then the car sat in very frigid MN weather for a week. It sat through our huge snow storm and the -25 degree windchill! The starter went out and that's why it was sitting. It took me a week to have the time to change it. Now that it starts, it rns bad. Won't go above 2300 rpm or 68mph. Bought some MAF cleaner. Gonna use it later tonight. Hope that works until I can put some good gas in it.