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420a motor Continuous Popping when rpm's hit 2,500 and below

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0r1landoDSM

10+ Year Contributor
213
0
Nov 10, 2010
Long Island, New York
as im driving my car tends to pop only when the car is at 2,500 and below if i give the car gas and let go of it at 2,500 it will make 1 big pop followed by smaller pops after wards as the rpms get lower to 2k to 1,500 etc... anything above 2,500 is fine but it only happens when the rpm falls to 2,500. any idea what this could be?

i replaced coil with msd ignition coil, replaced plugs and wires cleaned throttle body. but still doesnt stop only thing i havent done is replace fuel filter but i doubt thats the problem.

my exhaust had split in 2 (b4 the cat) once and a friend had told me that when my car was popping he saw alot of black smoke and the fumes got stronger
 
Does the car buck while it's popping? If so, I'd pull the spark plug wires and see if there's any oil on them... The VC gasket going bad and dump oil into the spark plug valleys is a super common issue. Put a new gasket/valley gaskets on, blow out the oil, replace the plugs, and you should be golden if so.
 
Does the car buck while it's popping? If so, I'd pull the spark plug wires and see if there's any oil on them... The VC gasket going bad and dump oil into the spark plug valleys is a super common issue. Put a new gasket/valley gaskets on, blow out the oil, replace the plugs, and you should be golden if so.

yeah ill try an pull all 4 plugs 2 morrow, i only pulled 1 plug which was 2 days ago. i pulled the plug from chamber 4 and it was clean. ill check the others

no the car doesnt buck, and rpm goes down smoothly. my car use to buck during idle between 2,500 and below. i block off my egr vaccum and the bucking stoped but the popping hasnt when i drive the car. b4 i i blocked off the egr vaccum 1st gear use to buck at 2,500 and below.
 
yeah ill try an pull all 4 plugs 2 morrow, i only pulled 1 plug which was 2 days ago. i pulled the plug from chamber 4 and it was clean. ill check the others

no the car doesnt buck, and rpm goes down smoothly. my car use to buck during idle between 2,500 and below. i block off my egr vaccum and the bucking stoped but the popping hasnt when i drive the car. b4 i i blocked off the egr vaccum 1st gear use to buck at 2,500 and below.

Just the plug wire... You don't need to pull the whole plug. If there is no oil in the valley then that is not your issue. The coil pack might be on the way out, it was just a quick suggestion. If there's no oil I'll further read into the issue.
 
My question is where is the popping coming from? Engine bay? Transmission? Exhaust? Try and narrow it down some.
 
Just the plug wire... You don't need to pull the whole plug. If there is no oil in the valley then that is not your issue. The coil pack might be on the way out, it was just a quick suggestion. If there's no oil I'll further read into the issue.

what do you mean by "in the valley"? and i do have a lil thin dry oil floating on top of my valve cover if that has anything to do with it.

i replaced my coil pack with new oem coil pack still popped then i replaced the new oem coil pack with msd ignition coil pack and still pops LOL

My question is where is the popping coming from? Engine bay? Transmission? Exhaust? Try and narrow it down some.

exhaust

<iframe width="425" height="349" src="http://www.youtube.com/embed/gKF_5xOuLVk" frameborder="0" allowfullscreen></iframe>


^^^^^^ really old vid b4 i blocked egr vaccum. .. after i start the car you can hear the car bucking at idle when i press the gas slowly going up to 2,500 rpm
 
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Sounds almost like a rod knock to me (45s mark), from that video anyways... has the problem by chance got worse overtime?
 
I hear a pretty good knock or ticking noise in that video. Do you have a current vid with the hood open so we can hear better?

at 0:16 you can hear it but ill drive the car around ill try to show rpm's and hopefully capture popping

<iframe width="425" height="349" src="http://www.youtube.com/embed/JxCQQ3-MYgc" frameborder="0" allowfullscreen></iframe>

Sounds almost like a rod knock to me (45s mark), from that video anyways... has the problem by chance got worse overtime?

the engine is quiet now i guess it was knocking due to colds start. that car made lil pops ever since i got the car but ever since i got catback and testpipe the pops got louder

<iframe width="425" height="349" src="http://www.youtube.com/embed/zmUlsEuVLZQ" frameborder="0" allowfullscreen></iframe>

All I could hear was either bad lifter tick, or an exhaust leak maybe.

yeah your right at the time that i made this video my flex pipe was leaking pretty bad.. that video is pretty old
 
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How exactly is your egr blocked off? Looks like you just disconnected the vacuum line. I remember when I first blocked off my EGR, the plate wasnt all the way tight and there was a little gap between the block off plate and the head, and it made little "clicks" almost, but once i redid it and got rid of the gap the sound went away,
 
How exactly is your egr blocked off? Looks like you just disconnected the vacuum line. I remember when I first blocked off my EGR, the plate wasnt all the way tight and there was a little gap between the block off plate and the head, and it made little "clicks" almost, but once i redid it and got rid of the gap the sound went away,

yeah, your right its not exatcly blocked off i just plugged the vacuum line with a small bolt
 
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