giumela

iTrader: (1)

I always here this noise and initially I thought I was hearing things. As I wait a couple of minutes for the car to get up to temperature I hear a pop or knock soming from the trunk or close to it. It happens everytime no matter if it's hot or cold outside. DOes anyone know what this is all about. Is the suspension stretching out(LOL). WTF is that noise? Thanks

MalibuJack

iTrader: (5)

It might be the gas tank bloating or venting pressure.. You may want to take it to the dealer to be certain the return line or charcoal cannister (vent line) isn't blocked..

90GSX-03EVO

iTrader: (27)

I get that too. I never heard it in my 2003 Evo, but now that I have the RS, it's very evident. Right around the same time as yours does, just after the temperature gauge starts to move.

I thought maybe it was the exhaust valve. Like maybe when the car starts and is under "fast idle" that it was enough to push the valve open, but once the car starts to warm up, it loses that extra bit of pressure and closes. However, even a 1500 RPM no-load idle shouldn't be enough to make the valve open up.

It sounds like it is comming from the passenger side rear, doesn't it?

giumela

iTrader: (1)

Yeah...you're dead on....that's where I always turn my head....to the passenger side rear. Your theory about the exhaust valve may be right.....although I thought the valve only opened at high RPM....who knows ...but that noise is there all the time.....still not a good reason to get an MR though.

WannaRace

iTrader: (15)

I posted concerning this noise almost a week after I got my '03 Evo. I have an aftermarket exhaust and still get the popping sound. I brought it into the dealer and they could not diagnose the problem, so I guess it's not then All is well even a year and a half later

jude

Exhaust valve? What are you guys talking about?

MalibuJack

iTrader: (5)

There's a valve inside the stock muffler that lets it idle and cruise quieter, but the muffler "Opens up" at higher RPM when the pressure is enough to push the valve in the muffler open.

I don't think its that though.. But I honestly can't suggest anything other than the suspension settling, or the gas tank bloating or relieving pressure... Those are the only two things besides the exhaust system that can shift slightly as the car gets warm..

jude

I get a little popping even at warm idle but I always thought it was either the exhaust system expanding or, like someone else said, the gas tank venting.

giumela

iTrader: (1)

I wonder if Mitsubishi knows about this....not that it is a problem....but I would like to know what is causing the noise. I bet if you took the car in and had some aftermarket parts installed they would probably blame it on that. I am holding back from telling the dealership about it because those guys at my dealership are pretty big tardos.

90GSX-03EVO

iTrader: (27)

Suspension settling would be strange, along with the exhaust valve. I've done a little "testing" on this now, and even did a "cold start drive right away before the car warmed up" and found that even after a minute or two of driving through a parking lot, when I would come to a stop, or even a slow cruise, I could still hear this pop right about the time that the water temperature gauge starts to rise. If it was RPM specific, or speed specific, then you might be able to say it is components settling or expanding as they warm up. This isn't the case, though.

What is it? I don't know. Now that I have a radio installed in my RS, I just turn it up as soon as I start my car so that I don't hear the pop.

It only does it once, and it only does it when the car has sit and cooled off completely (water temperature gauge is all the way down). It quite possibly might be linked to that strange boost gauge phenomenon encountered when people would tap their boost gauge in to the fuel pressure regulator line. It would work fine when the car was cold and started, but once the car heated up, if they turned the car off and then started it again while it was still a bit warm, it would hold their "peak" boost instead of instantaneously falling off like a boost gauge should. How could this be related? I don't know, but something tells me it has to do with the fuel system (due to audible direction of the pop)and the car being either cold or hot.

Punisherofall

I get this noise as well, and I agree that it is the stock muffler "flapper valve". It "pops" when the rpms start to go down from abot 1500rpm to about 11-1200 rpms after cold start up, so I think it is possible that the flapper door does open up with the high idle. Just my 2 cents.
Stay safe,
Punisher

90GSX-03EVO

iTrader: (27)

According to people on this thread, it's been known to do it on cars with aftermarket exhaust as well.