this is something my car has done since i got it, and it hasnt really ever been an issue, but lately, its gotten worse.
96 2.2 5 sp, intake/no header/cat back, full rebuild (only factory parts are the pushrods and connecting rods, everything else is melling/sealed power/federal mogul/clevite/comp cam) at 86,033 (previous owner never changed the oil after 25,000) i've been changing the oil every 2,500. i dont use fuel additives, i very rarely use injector cleaner, i've cleaned my TB/IAC/upper plenum. i've changed plugs twice (from bosch [worst] to delco [a little better] to ngk iridium [idle VERY smooth]), plug wires, tried different coils, even resetting the computer by leaving the battery disconnected for 6+ hours. new battery, new alternator.
the symptoms:
i get a very loud POP coming from the intake (i know its from the intake, because once i installed my short ram its MUCH more pronounced) only,and here's where its weird, ONLY when i'm quick shifting, after i let off the clutch and get on the gas.its almost as if i get on the gas,it pops, the engine looses all power, but it keeps running, and comes right back to life. i KNOW this isnt normal, and like i've said, its done it since i had it. but tonight, on my way home, it started doing it on my normal shifts, three times in a row (2-3,3-4, and 4-5). its starting to get me worried. i've talked with a few of the mechanics in the area, and its got them all scratching their heads, even after a test drive. i had a thought occur to me this evening, would it be worth it to me, on my next fill up, to try a higher octane gas? i've tried everything else i could possibly think of, and it still does it. help me jbo, you're my only hope...
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did it again today, but only once, although it was real bad. engine rpm/vehicle speed doesnt seem to make a difference. though i have noticed, that the further opened the butterfly is, the louder the sound is.
only thing i can possible think of are as follows:
bad ignition module. but i think i can rule this out because the car wouldnt run at all if it were.
bad gas/too low octane. again, i think against this because a)doesnt matterwhere i get my gas from, still does it, and b) stock compresion, oem replacement internals, stock thickness headgasket.
bad/slow iac valve. in theory, this could do it. as the butterfly closes, the computer notices the tps closing, and opens the iac to compensate. reopen the butterfly too quickly, and in theory, you make a lean spot.
bad tps. same idea as above, only if there's a flatspot in the tps, it could also cause a lean condition.
now, i should mention, i've NEVER had a check engine light come on on this car, except my persistant p0440 light. it does come and go, seemingly out of nowhere. idles smooth, very little valvetrain noise, only when its cold. i cant for the life of me think of what my next step should be.
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Maybe a sensor is going bad and is not compensating for the air coming in.
It can also be the timing.
Did you tune the car after doing all the motor mods?
Also, did you check your plugs?
plugs always come out clean.
timing is fine, as it idles fine, and is rather smooth sounding up through the powerband.
now, what exactly do you mean by tuning? everything i put in was oem replacement, as i said, stock compression, stock grind cam. even if i wanted to tune it, having a 96, i couldnt.
i also have not changed the o2 sensors, either one. they're both stock.
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it runs fine with normal driving? or when you get on the gas hard? i have had a simular problem with mine awile back it popped like urs does but it was running off 3 cyls it was the injectors got em cleaned problem fixed. and the last time it would run good when ever it wanted to usually cold it would run fine till i got on it hard or it got warm then it would pop out the intake , it was the coils. that was my exp hope it helps some
it doesnt really matter how im driving, i've been driving slow through a neighborhood and it popped pretty good, and i've been running all out and it popped as well. as i said, engine load/rpm seems to have no factor in this. i figured i'd run some seafaom through the tank tonight, and it's not done it yet. it actually seems to be running even smoother than it usually does, which is rather strange, because it already runs smoother than all the rest of the 2.2's around here (lots of old people and kids with s-10s.) coils as i've said, i've tried known good ones and it did nothing.
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As far as I know.. this is how the sensors work. (someone that knows for sure should really make a sticky saying what sensors and signals are used to control spark and fuel and stuff like that)
The IAC runs off of the rpm, not the tps or map.
I think the only thing the map sensor is used for is timing / load sensing.
The car reads the tps and rpm (along the the O2) to control fuel
I belive timing advance is diceided by reading the map and rpm.
The only time I've ever seen a backfire out the intake (without nitrouse being sprayed), was when either the timing was way off or the firing order was wrong. (both on cars with drstributors). Either fuel is pooling before the intake vavles and igniting, or the timing is getting off enough thats the spark plug is going off around the same time the intake valve is open.
If I had to guess... I'de say your injectors are just really dirty or worn out.
yeah, im now thinking dirty injectors too... since put seafoam in it, it feels like a new car. and it hasnt popped once.
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^^ good to hear... hope it keeps running good for ya.
