BANG-POP-GRUMBLE SHAKE. whats wrong now?!!!

General discussion forum about the 240sx, and a great place to introduce yourself to the board!
Jam-Dodge
Posts: 71
Joined: Fri Apr 13, 2012 4:20 pm
Car: Nissan skyline R33 RB25det *Forged*

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i've got this s13 running good with the boost leak fixed but the backfiring (and thats all the time) still happens

It only happens when i change gear from low to high and vice versa, and also if i rev the engine few times and when revs start to drop and go down then theres that "bang pop" backfire and i'm allways getting this raw fuel smell in the cabin.

although it turns heads and sounds kind brill!! :chuckle: i'm only getting about 10-15 miles to gallon. and thats sensible driving.

now the worst grumble is when downshifting ie: coming in fourth gear about 40mph then downshift to 3rd and slowing down i get a BANG POP GRUMBLE all the way till the revs go down to about 1200-1100.
i've replaced the air filter but no good backfire and grumble continues. so need some help to get this sorted thx

another thing that allways happens is when i get to start the car everytime, it starts up shaking and revs stay below 1000 choke struggles to come on sometimes i'll increase the revs slightly by the rev peddle so that the revs read about 1300-1400. even so it struggles to stay put i mean the revs are allways bouncing choke struggles to come on 50/50. so when i get it driving and come to a stop the revs may go stable but engine is still shaking that it can be felt within the car and gearknob is shaking at the same time, now i have'nt got a clue why that is, a friend of mine said maybe engine mounts but when checked they all looked good but on of the engine mounts under the intake manifold was missing the nut :eek: , could that cause a condition like this i will be replacing that 2morrow though pls guys help me out with this one. thx


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Ziggy1621
Posts: 1137
Joined: Sun Jun 10, 2012 5:57 pm
Car: '90 Z32 TT (Shibui)
'90 Z32 2+0 NA
'68 311 Roadster
2004 Rx330
2011 BMW 550i (TT)
Location: Cocoa, Florida
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What mods do you have?

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Syrus33
Posts: 112
Joined: Sat May 30, 2009 6:52 am
Car: 1993 Nissan 240sx Hatch
RB20DET

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Sounds like its dumping way to much fuel

Jam-Dodge
Posts: 71
Joined: Fri Apr 13, 2012 4:20 pm
Car: Nissan skyline R33 RB25det *Forged*

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well as far as i know the engine dont have too much mods but its got at the mo:

fmic
straight throgh exhause
bailey dumpvalve
boost conroller ( manual )

and thats it apart from that its all stock

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Morph
Posts: 2520
Joined: Sat Dec 13, 2003 9:02 pm
Car: 91 Sr Powered Coupe

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What size injectors, and what kind of Fuel management are you running?

Im guessing this is a KA-T????

Jam-Dodge
Posts: 71
Joined: Fri Apr 13, 2012 4:20 pm
Car: Nissan skyline R33 RB25det *Forged*

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as for the injectors i've got stock 370 and no added fuel management stock pump, yep its a ca18det engine 1.8T

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domicubarican
Posts: 95
Joined: Wed Jun 04, 2008 9:01 am
Car: 1989 Nissan 240SX hatchback *sold
1993 Nissan 240SX coupe
Location: Fort Worth, TX
Contact:

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had the same thing happen when I had my ca18, everytime i downshifted it'd do the backfire-grumble. Maybe fpr is going bad? Or could also be that you have straight-through exhaust...no cat to burn off excess gas/fumes coming out the exhaust

DaniMike
Posts: 172
Joined: Fri Feb 23, 2007 2:55 pm
Car: 1993 240sx, 1996 240sx, 2008 Altima

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My KADe did the same thing after I got Nistune and had a tad more fuel added. Basically it is just unburnt fuel in the exhaust, it won't cause any problems. Sometimes I can rev it up pretty high and quickly drop the RPMs and get a little flame out the pipe! LOL


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