MY18 86 intake backfire on throttle blip downshifts
 

Hey everyone,

Just picked up a new MY18 86 GT manual (with the updated fa20 engine, red intake manifold)

I have noticed that I hear the distinct intake backfire sound on fast input throttle blips when downshifting gears, the same popping sound that the engine makes when the DI seals failed on 2012 cars.

I can't replicate it all the time but its happened 4 times so far in the week that I had this car.

Car only has 550km on the clock.

12/2017 build

Car is completely standard.

No codes are shown.

From what I can tell it happens when its up to operating temperature.

I have sprayed carby cleaner on all the intake joins, throttle body and where the DI injectors are seated to the head and no obvious air leaks that I can spot.

I try to free rev the engine and blip the throttle while the car isn't moving and I can't replicate the issue, only when its driving. Even then I can't purposely replicate the issue while driving.

My 2013 86 GT never did this in the 100,000km and the many, many track days (abuse lol) that car was put through.

Anyone got any information I can use for when I take this to the dealer? I feel that I'm not going to have a fun time with this issue.

Well, now, that's too bad that you sense your new car isn't working right....:(.

With 550 km on the clock ....... the engine is brand new ....... maybe it needs to run a few more miles to sort itself out ... ??

Maybe it doesn't like that first tank of gas ....... maybe insure it has top tier gas in the tank.

Since you aren't a stranger to the FA20 engine, I predict that you and the dealer will have quite a go around.

Maybe ask them to re-flash the ECU ..??


humfrz

Already on my second tank full of Shell 98ron fuel. Don't know what fuel was in the car when I picked it up. Wouldn't be surprised if they put 91ron fuel in it to save a buck.

Re-flash the ecu into what? His car is brand new.

This is quite possible. Let us know if the issue is solved.

I realize the car is new. I was thinking that maybe the ECU wasn't set right from the get go ...... :iono:


humfrz

The dealership won't do anything and can't warranty what they can't replicate. So keep driving since it is driving well. If performance goes to hell or the noise is constant or if a CEL comes on, then take it for warranty work. Don't sweat an odd noise yet, it's probably nothing.

I have a MY 2017 86 with 5000km's, it makes the exact same noise you are describing. I notice it's only after the engines been at a low and relatively steady state rpm. On occasion if I rev match down shift it makes the popping noise, and it can be heard from the sound tube in the passenger side foot well. It startled me a few times but it's definitely been happening since it was new.

Out of curiosity have you changed the Air filter to a high flow one recently or modified the snorkel at all?

Edit: forgot to add It happens on both Shell V-Power 92 and Ultra 94.

My 2017 does this too. I've also heard it in my buddies 2017. I've swapped to the older air box and k&n filter, and it still does it, so I don't think it has to do with the 2017+ air box. In his car, it's much quieter with the sound tube plugged.

It only ever happens when I mess up and give it way too little gas when rev matching. I don't think it's a big deal, just give it more gas when you're down shifting.

Ignition retard during Transient Map is MUCH more aggressive on my17+ cars
that's what s causing the bangs during fast downblips
no worries
lower octane can contribute to create them, cause if AM stays down, afr is richer and timing are even more retarded
still, no worries

Totally normal, if it bugs you just plug it with a sound tube delete.

I get this on my 2013 when running the 2017 TIR table. The only way I can sometimes reproduce it is when I am off throttle in a high gear where the revs fall off very slowly (for example coming up on stopped traffic on the interstate). So for example I am decelerating in one gear without touching the throttle for 10 secs or so and then go to do a blip it pops in the intake right as I tipin. This is the only scenario I've encountered this pop.

I am in the process of an engine rebuild and my DI seals looked fine so I know the pop isn't a seal problem. I agree with tomm, it's to do with the extreme retard the 2017 TIR table has. Because I only started getting this pop when I changed my TIR table.

This is good to hear, I figured it was normal but wanted to make sure.



Thanks everyone.

ok cool. that's good to hear. i just assumed my DI seals were gone after 500km.

thanks everyone for your input

Backfire normally results in catastrophic failure.