Thread: Hard Start and Backfire after new plugs

are you running maf or map? the backfiring and the inconsistant air fuel reading got me believing its some sort of issue along the map or maf lines depending on what you are running...maybe bad o2 sensor getting you odd air fuel readings and offsetting your whole fuel and ignition tables?

Will a bad 02 cause startup issues? Thought the 02's didn't come into play until after warm-up?

^^ IIRC O2 shouldn't mess with starting the car.

i was refering to the issues he was having after warm up and the whole odd air fuel ratio issues.

So, re-reading the OP, are you SURE it's a backfire, and not a misfire?

Haha, yea, I am going to retry the old plugs and see if anything changes. If so, I'll just go get some NGK's heh.



Just stock maf setup. I am going to re calibrate the O2 gauge, because it just seems too wrong to be true. My engine should have blown up a long time ago.

Although I just recalibrated it under a month ago =/.





As far as I know, the O2 sensor is only used for feedback at idle. I thought it was totally irrelevant for the ECU maps at anything other than idle???



Sounds like a backfire, and the uneveness of it in volume and frequency also point to that.


But for now, I will have to look into this stuff. I am moving though so I won't have time till this weekend. I might start another thread that is more general, because I'm starting to think this isn't just a plug problem. =) More likely is that the plugs are just showing me an issue was already there but hidden.


One last question: Do the injectors fire every revolution during engine braking? For some reason I thought they did not. I know it's normal to run very lean on engine braking, but I was just unsure about this.

I'm pretty sure by pack fire he means a pop sound coming from the muffler from the rich condition. Not a real back fire where the explosion goes back into the intake.

I was under the impression that is what backfire meant lol! Am I mistaken?
I thought the intake thing had a different name. Guess it really depends on your point of view. =D

Nah, backfire is firing back to the intake. If it's popping as it exits the exhaust, which is more common and much less of a problem, it means your a/f ratio is off and you've got some unburnt atomized fuel coming out. With backfiring you're looking at valve float or messed up cam timing.

Don't worry about 90% are confused on that one. Reason is it makes more sense to call it back fire for non-technical people. All they know is there is a fire in the back of the car haha.



Yup that correct. Now I wonder what would be the technical or more correct word for exhaust firing. I found myself having to have to say Back Firing just because it's easier and the people I'm talking to aren't as confused