norberts94fd

i just bought a 94 rx7 and it sounds like the exhaust is popping when i turn the car off and sometimes when im giving gas.Also if i rev the engine when its in neutral sometimes it almost dies out when it comes back down to idle. does anybody know why its doing this,the car is all stock besides a down pipe, any info would help.Thanks

weetbix13

running rich... how does it drive in general?
if there is lots of black smoke and boost seems off, then i'd say it is your map sensor or a boost leak.

the best way to get help in this forum is to:
1. use the search tool... in this case searching for 'backfire' and 'idle' would have bought these up 100 results: https://www.rx7club.com/search.php?searchid=1604740 - search, use it, love it.
2. give us too much detail, tell us everything including boost patterns, mods, things you've tried, things you've checked... everything!

cozmo kraemer

Mine backfires too ! I always took it as one of the rotary quirks...I kind of like it; the burble and pop.

As long as it isn't anything extreme, I dont think it is anything to worry about.

What mods do you have?
Tuning?
How does it backfire? Specific situations?

riptor

mine only started after i put on my hks hi-power....like cozmo sed i kinda took it as one the rotary quirks...tho the exhaust does smell a little rich at times......normal opertion..?

weetbix13

running a bit rich and light popping is a quirk... when it almost dies out when rev'd and put into neutral means it will be doing it at lights etc too.

thats an idle cable adjustment, map sensor, idle control or a whole myriad of things.
more detail?

twisted7

iTrader: (3)

i have the hks hi power and it does this as well nothing special just get a midpipe and downpipe and pfc to control everything and ull be good..along with intake and all the other mods to support it

BLKTOPTRVL

Mine idles a little irratically and I hear a pop every once in a while. When I shut down I always get one last pop before the engine is still. I read somewhere that it might be a bad O2 sensor... but I am not mechanical, so I can't say for sure.

weetbix13

you guys should all adjust your idle up then... just tighten the bolt on the throttle cable on the IUM... or the throttle control. why are you living with an idle-out issue?

=oP

SiKoPaThX

iTrader: (2)

What in the hell are you talking about? Ways to fix backfiring and the car dying are not adding performance modifications.

I would check things like Throttle Position Sensor (TPS), MAP sensor for now. We need more details about the car though.

BLKTOPTRVL

My car idles at 850... Which I believe is where it is supposed to be. Any other ideas?

weetbix13

BLKTOPTRVL yours is fine at 850 and a little lumpy. mine is a bit lumpy tuned to 900rpm.
Sikopathx is right though... anyone who says that something is wrong with their car and the best way to fix it is to put on a performance mod is putting thier car on a fast track to the mechanic.

erratic idle isn't that high on the list of death symptoms, but that is just general bad advice for a first time poster.

BLKTOPTRVL

Agreed on both points...

As for my idle, I would love to have it as smooth as my vert (like glass), but really, it is just an annoyance I would like to lose. I'm just hoping someone might come up with a good suggestion for a fix.

BTW, does anyone know how to extract/read the stock MAP? Maybe there is a hitch in the tuning.

Snotcycle

i think the idea behind putting on the downpipe and stuff was to lean the car out a bit, not total idiocy but imho these cars don't take well to ghetto rigging unless you're Adam_C.

weetbix13

leaning the engine out has to occur before the combustion process to the best of my knowledge though... it is all about air/fuel mix - exhaust only figures in at high rpm/boost.

theoretically, the downpipe and exhaust will increase the flow of air through the exhaust turbines of the turbo by removing backpressure from changing exhaust gas flow direction and removing restrictions/variations in pipe diameter thereby increasing boost spool speed and pressure. it won't affect running lean/rich unless at boost levels that the ECU doesn't have maps to compensate for any more.
The ECU's on the FD add fuel based on air flow at given boost and rpm; it is an air measurement guided process. to lean it out you'd need a piggyback fuel computer, new ecu or some ghetto rigging in the MAP sensor lines.

i could be very very wrong.
but i just love when Mahjik and Deegsman post... those guys are legends.

MAN, i learnt a LOT during my rebuild!

Rocking Rotary

iTrader: (14)

no cat = backfiring if you dont have a cat to burn of the extra gas then it will back fire and you get nice fireballs out the exhaust.

If you dont like the bakfiring and a highflow cat and that will take care of it. Happy rotoring

Gadd

There is no reason your stock car shouldn't idle "like glass". Check the obvious first, how old are the plugs and plug wires? Vaccuum leaks (very common cause of idle problems). Malajusted idle air screw. Malajusted TPS. Sticky Idle speed control solenoid.

The O2 sensor has nothing to do with the idle.

weetbix13

not likely to idle like glass during warm up though.
when first starting the ECU enriches the mixture in an effort to bring the cat up to optimum operating heat... during this process the rich run would cause a couple of lumps.

mine lumps until it has been driven, then goes so quiet you'd genuinely beleive it had no apex seals (again).

DriftTrix

My cars not very stock at all anymore but after a little tunning with a autronic ecu it fixed the problem.. It came back up when i forgot to plug in my TPS, it would back fire when i got off the gas. Mostly it has to do with tunning, your car just injects a little too much fuel when you let off so it backfires. If its really annoying you might want to get it retuned but its not that big a deal. Some flames never hurt nobody.

riptor

ok to clarify....modz in sig...have had the intake for a year now...and i just got exhaust..just changed the spark plugz as well..everything else if stock..i have a class in the am but ill go mess around with the tps and idle control tomorrow hopefully.... in the mean time...any more ideas??? i know im not he only one to read this and be able to relate with the situation...

cozmo kraemer

I had a crazy idle and some backfiring issues before I installed the PFC. I adjusted the TPS to be just about spot on. I cleaned the ISC and played around with the air bleed valve and the coarse adjustment screw. Nothing worked...

I installed the PFC and after about a week, my idle was smooth as glass. I still have backfiring when letting off of the gas at times...a burble, burble..pop pop...nothing extreme...but this is WITH a high flow cat. I realize now that I am just running REALLY rich.

I didn't catch a detailed description of your problem in this thread. Perhaps you could better define what is happening??

If it is an off throttle thing, then I would say tuning for sure (just running too rich)...if it is dying at idle, or stalling out as you get on the gas then I dont have much experience with that...

point5chink

I dont beleive this is true. Removing back pressure allows more exhaust to exit the combustion chamber, which then allows more air in on the intake cycle. Basicly, faster easier moving air out = more fresh air in, thus leaning out the mixture, even at the same amount of pressure.

weetbix13

you make a valid point, and i have to acknowledge that moving the exhaust ports to the side on the RX8 was in an effort to reduce the intake/exhaust overlap however i'd imagine that is pretty negligible. the design of the 13B-REW would mean that backpressure would slow the rotating assembly rather than transferring the exhaust gases to the next cycle right?

i.e. pressure is flowing directly against the back-side seal of the rotating combustion chamber... i'd assert this based on the fact that there is a direct path from exhaust port -> turbos -> downpipe rather than an extractor assembly.

RE Suzuki

I have m2 stage 3 ecu, intake, down pipe, high flow cat and rsr catback.
frequently, when I down shift or rev the motor up and relase the gas pedal on nutral, my car backfires like,"pan! pan! pan pan pan. . ." it's starting to get annoying...