YOUWSH

Ok not sure if anyone gets this but I was reversing my car into a car park space and obviously I was revving the car a little as I was slowly reversing in. Every time I rev and let off the gas I get a very loud backfire which scares me most of the time let alone the people walking past.

My car also does this if I'm in 1st gear and again rev and let off while I slowly move forward say if I was heading into my garage.

Can someone explain this? The pops from the backfire are pretty dam loud as one of my friends describes "sounded like a shotgun" particularly in an enclosed parking lot.

bryant

what upgrades?
maybe tune.

YOUWSH

Stock ECU with just a few bolt on.

silverTRD

iTrader: (37)

my car did the same thing with the stock ecu and a greddy ti exhaust. the stock ecu runs pig rich. my wideband would be in the 9's at wot.

finneymc

did you ever find a fix for this? i just had my fuel filter and sparkplugs changed so i don't think that is it, but i am having the same problem and it is annoying.

Thanks,
Craig

spaceman_spiff

is backfiring okay for the exhaust system? or does it damage something in the car?

tiger18

iTrader: (1)

Ive got you a little something to look into,, i read somewhere that if the dashpot is no longer doing its job of slowing the throttle closing speed down then this can cause backfiring, just something to look at.

finneymc

you got a link or something to where i can find any info on a "dashpot"?

thanks

DaveW

Any chance you have a slight exhaust leak? When you let off the gas, air will be drawn thru the leak into the rich partially unburnt mixture in the exhaust, causing it to ignite, and this could be the backfire.

Dave

tiger18

iTrader: (1)

There a section in the service manual explaining how to check it i beleive.

finneymc

well i dont have a service manual.....but i will check for exhaust leaks this weekend

thanks

BigWillieStyles

Backfire is normal for FDs, and is just the airpump removing unburnt fuel from the exhaust. I wouldnt worry unless its seriously loud and aggressive. If your worried about it, you can remove the air pump, but i would assume that it would make the car really smelly and maybe even clog up your cat!

Ive never been in an FD that doesnt pop on slight acceleration and downshifting during bursts of acceleration. Its just your car doing its job. Ive heard that JDM cars, are more prone to backfire as they dont have a pre-cat.

I think its just part of the character of the FD, and makes me feel good its not some boring Honda!

00SPEC

iTrader: (9)

+1

bryant

this should make it a little easier.

https://www.rx7club.com/3rd-gen-archives-73/tech-manual-directory-614824/

finneymc

Since i have taken out the baffle(silencer) the backfiring has been getting worse and worse. I haven't checked for an exhaust leak yet, i am going to check 'er out this weekend. Is there any known fix to at least com down the backfiring (japanese people are pretty big on sound pollution)?

BigWillieStyles

Well there is almost nothing you can do to stop light popping as thats just the FD, but if its really bad it would be a indication of something else.

Is it just popping when you are downshifting and light throttle or is it this bad...

http://youtube.com/watch?v=0GsNdHej1qM&feature=related


Japanese have strict laws of 95db only. Anything over that is illegal and wont pass shakken.

finneymc

it is mainly when shift from 2 to 3rd and letting off the gas in reverse but it isn't just "light popping" that **** is loud as hell! It is kinda funny being on a military base though and seeing the reaction of a grp of marines when it happens right next to them! lol But yeah it is pretty loud but only when shifting and letting off the gas.

thanks

Grassninja

I too have the same exact symtoms with my '92 FD. I took it to Reaction Racing in Sagamihara district in the outskirts of Tokyo and they diagnosed my problem being that my compression was near to nothing. On a fresh running rotary, they said that I should be getting a compression ratio of 9+. My results were far from that...7.9 on the back rotor and 7.1 on the front. Not good! They told me that I needed a complete rebuild at anything less than 7. Next week its off to Reaction to get the rebuild...looking for a few more horesepower and resolution to that ungodly backfiring. Little loud coming out of a 3" exhaust

finneymc

well the 7 had a compression test about 5,000km ago and they were both at about 8.4ish so i don't think that is my problem. MAKERS says that my 7 is perfectly fine and that the backfiring is okay, so i guess i will have to learn to deal with it

thanks for your info

jmadams74

Same issue here. Was wondering if the RB dual tip might calm it down a bit?

Oliv

Your compressions look ok to me!

Below 6 I'd start to worry.

YOUWSH

I never figured out this problem before I sold my car but on my new 00 I don't have this problem.

Interesting to note that when I installed my Power FC, this same problem came back but only slightly.

Dudemaaanownsanrx7

iTrader: (23)

it's probably overly rich. You could get a PFC and tune it out, though thats a more expensive option just to fix popping, the PFC is definitely worth the $$.

I suppose you could change out the o2 sensor too, this is probably in the area where it should be getting feedback from the stock 02.

seanfd3s

i had this problem the timing was off and it was pop like a rally car at 1000rpm limping to work constant pop pop pop; disconnected the ecu and reset it and it went back to normal.

kungpaomaster

Check your vacuum line to the boost sensor thingy (highly technical, i know). When I changed the plugs one time I accidentally managed to bump it off. It has the blue check valve in the line and attached to the drivers side, top of the firewall. Ran like sheeeot. And backfired abnormally if that makes any sense. Plugged it back to the boost sensor and it solved the problem. Could be that easy.

Good luck.