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why my car only backfires at certain times?

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Just wondering why my car backfires at different times let's say one day it will backfire and spit flames every gear change well only when im on max boost for a few seconds then change gear bang. Then some other days it just doesn't do it at all? is it the weather, is it the heat of my engine?
 
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fuel mixtures, fuel quality, fuel pressure reg not working as it should, you ecu getting a incorrect o2 mixture reading and putting in too much fuel, anything to do with your fuel basically
 
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Usually over fueling on run off and with the heat of your exhaust it ignites causing flames and back fire. Do you still have the CAT?
 
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interesting thread because my car has always spit and popped once hot right from when it was standard, after a few mods including straight through cat it pops loader at roughly 2,500 revs but noticed a little hole drilled in the silencer just before the back box and thought it was that as was told air leaks can cause this noise,,,,, not funny when iam driving at 5 in the morning :eek:
 
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Jared, it comes up in fast as a genuine Spec R, 6MT (when it left the factory in japan it had the SR engine that you want). however as me mate Aus noticed, the intercooler cold pipe has got a S14 resonator on it?? the owner may of just put a S14 side mount in, may have removed a front mount who knows, as its missing the shroud for the fan too so it has been tinkered with but then again 90% of Silvias have, its no cause for alarm, or it may have had a engine swap. Ask him to email you a photo of the injectors DONT ask him what colour they are, purple are S14 turbo or S15 turbo automatic 380cc, orange/terracotta are S15 manual turbo 480cc, and a couple of good photos of the engine bay, if you go up and have a look at it, take a pen mirror up with you and look for the plate on the turbo center housing for this number 14411-91F00, that way you will know its got a Spec R T28BB.

If the rocker cover has got nuts holding it down then you have defiantly got a early S14 engine, but i cant speak for the later 97, 98 S14 SR20DET's they may have bolts holding the cover down like the S15 SR20DET's did.
If looking at it, listen to the engine idle very carefully, learn to define between injector noise (sharp very short clicking) and noises like lifter tick, VVL rattle and rod knock, also go to the back of the car and get someone to give it a little rev and look at the exhaust for blue ish smoke.

Listen to the gear box, noise clutch in and clutch out, go through all the gears ( all 6 forward ones ) feel for worn syncros,

Hell its worth booking the car in with ST Hitec for a 15min look over as in getting the guy to meet you there, wont cost too much and Soichi will tell you straight away if there is anything not right, i recommend him as he was in nissans engine design team when he was in japan.

Look for these bits on the car too, http://forum.s15oc.com/showthread.php?9933-JDM-Spec-R-Body-Bracing-info-compared-to-JDM-Spec-S
is the cluster black like yours or is it silver?

if you havent figured it out all ready, dont take the sellers word for anything, everybody lies when selling cars
 
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