backfire/pops low revs first start

[kieranc182]

Hey all ive noticed when i let off in 2nd gear at 2-3,000rmp to slowdown for the top of my street the car will backfire or crackle and pop, i thought it was a one off till the other day i accelerated in 1st gear gentle changed to 2nd and took it to 2500 let off crackled and popped and did it again and again to make sure it wasn't a one off, ive noticed it stops doing it when the auto choke turns off and the revs drop back down to normal idle, is thi due to it over fuelling with the choke on ?

 

[DannyR]

A choke? Is yours on carbs?

Sounds like a misfire.

 

[kieranc182]

i presume the car has some sort of cold idle thats slightly richer than what it would be if it was warm or something along those lines , and it doesn't misfire it accelerates perfectly fine its when u let off it pops and crackles but only when its on cold idle 1200-1300 when its cold dropps down to just under 1000 after around 5-10mins :/

 

[kieranc182]

They use a coolant temperature sensor to tell the ECU to adjust the fuelling when cold

 

[DannyR]

Lol I know, but chokes are only used on a carbureted car! I was joking around.

Could be CTS, lambda or injector related. Best get it on a CLiP computer or other decent diagnostics.

 

[kieranc182]

, to be fair i think its is cts because it can be at temperature ages before it will let me have the raised revlimiter :/

 

[JonnyGee]

do u have a straight through decat?

 

[mad in general]

totally standard 172 ph2 here and i notice that when warmed up and thrashing it i get a lot of pops n bangs on the over run. Is this normal?

 

[kieranc182]

yeah its decatted, but it did it before i fitted the decat just now its louder lol

 

[Johndolan1979]

yeah its decatted, but it did it before i fitted the decat just now its louder lol

Don't worry about it, mine does this as well when cold. If you lightly tap your accelerator whilst your off the power you'll get more pops and bangs. I believe it's over fueling whilst cold, mine is running a straight through and decat as well.