Ok , so here's the story. My z has a remote start which requires you to put in the key and press the brake before you can drive the car(obviously). So one day i was entertained i put in the key but didnt turn it to the "start" position and i pressed the brake the car startes turning off but i quickly turned the key and it came back on before having to crank the car again. BUTTTTT then i noticed the car backfires whenever i let off the gas and i was wondering.

I have tried it on other z's and g's and they all do it. If you dont understand what im saying try this.

1) turn on the car. In nuetral
2) rev it a couple times( you shouldnt hear any backfire or popping)
3) hold in the clutch
4) quickly turn the key to the 'off' position and back on to the 'on' position.
5) now rev a couple times and the car will back fire.

Anyone know why it does this? BTW i found this out by mistake.

 

Anyone able to log and see any differences?

 

Backfiring in a car with cats is not a good thing. Your ought to avoid doing that.

 

People used to to this in the 90's. looool

 

Any reason you are trying to turn off and turn back on quickly? I cant imagine this is good for the starter/electrical system...

 

It's called unburnt fuel clogging up your cats... don't do it.

 

I dont do it on purpose likei said i found this by mistake.

I know what backfiring is, the question is why does doing that cause the car to backfire?

 

So you are investigating something that shouldnt happen that you found by doing something you shouldnt do?

 

Soo whyy do you come into a thread and ask questions not related to a possible solution? Its a car forum where you ask questions to learn more about your cars engine , etc. I want to understand what changes when i reopen the switch that causes the backfire whether its good or bad i just want to know whats causing it.

 

Correct me if I'm wrong but didnt you say it happens when you turn the car off (turn key to off position), then immediately turn it back on?

 

Thats not how i found out initially but yes thats how you can duplicate it.

 

Well, this may sound stupid, but it may be because when you are shutting the car off and starting the engine within a few milliseconds, you could be screwing with your air/fuel ratio, which can cause backfire.

 

I was thinking something along those lines but i wanted to see if anyone was able to try it and check their afr to see if its affected or not. I also noticed the car decellerates alot more when you let of the gas.

 

When driving or just revving? As far as checking the AFR ratio when doing this, my guess is no one will want to try this

 

Driving

 

Your ought to avoid doing that.

 

Great post bro!

 

Its all about latency, when turn the ignition off, your coils respond much quicker and shut down spark immediately, whereas if your injectors are already in the process of injecting then that fuel will go into the cylinder, but it wont get burnt. As soon as you turn your ignition back on, and you introduce a spark, bingo, you get your backfire. It happens in most cars, (or at least the ones i've owned), but like everyone is saying, DON'T DO IT! It will destroy your cats, and next time you get an amissions check you will be very dissapointed.

As for why the car decelerates more, i couldn't tell you, i've never experienced it myself, but i would think it's because your fuking with the ECU, so stop doing it or some damage will happen.

 

Got it! Thanks

 

So its I ended up stumbling upon a motor that had gone through this and white smoke blows out the exhaust when I step on the gas, also has a lot of fuel and oil consumption where I’ll go through a whole tank of gas in under a week, and oil will be almost gone at 2000 miles from the last oil change I haven’t been able to figure out what it could be maybe a leak in the head gasket