Popping sound @ Idle when engine cold, any ideas??
 

Hey guys, I've got a 94 5.0 with mods below, and not that its a bad thing, but I get a popping sound that lasts about 1 minute when the engine is cold, and then disappears...

Also, until the engine is warmed up, power below 1000 rpm is weaker...

Any ideas???

THANKS GUYS!!

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94 Mustang GT (black on black)
K&N, MAC Shifter, FMS 9mm, 0017" rims, 3.27, 13*, MSD Coil, on a diet

I have that same noise at start up when car has been sitting for a while.

Been told that it has something to do with the smog pump warming up the car.

But mine didn't start to do it 'till I put in my o/r h-pipe.

Don't thing it causes any harm though.

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Green '94 GT conv. -- K&N filter charger, FMS 9mm wires, Accel hipo cap/rotor, 180* thermo, 14* timing, off road H-pipe in front of 2 chamber flow's, and still workin' on the rest!

My car makes a weird noise kind of like what your talking about, it sounds kind of like blowing air through a straw in water (it's not real loud), it does it when the motor's cold and sound like it's coming from the rear of the engine by the firewall. I looked under the hood and it isn't coming from my smog pump, although your noise could be something different from mine. If I find out where it's coming from I'll let you know.

I believe that it's just timing while the engine is cold. Your computer is constantly adjusting air and fuel so your timing is going haywire for the first 60sec. That causes a rich condition in your cylinders and backfires is what your hearing

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Blueneonman - '95 5.0L Mustang GT Convertible | K&N Custom Cold Air Intake | FMS 9mm Wires | Hollow Cats | Flowmaster 2 Chambers | BBK Subframes | 6-pt Rollcage | 14deg Timing | King Cobra Clutch | FMS Adjustable Clutch Cable | Coolest Neon Lighting on a Mustang EVER!

Homepage: http://www16.brinkster.com/blueneonman/

Best time: 14.578 @96.20mph

blueneonman1 you go to bithalo?
i go there all the time, i got a 90 red GT with ponies, it runs mid 13's.

Is your car a white vert with blue neons under the handles and stuff?

Thanks guys, but I went and got an oil change, and that fixed it all up (for $25 total), starts smoother, and idles better !!!

strange that oil would have that kind of effect???

Thanks again!

You're running lean, not rich. It's probably caused by your off road h-pipe. Use the search engine to find Rebel79's off road h-pipe fix. Your O2 sensor's don't work when your car is cold, you run in open loop, but my guess is your computer is taking closed loop info and adjusting your open loop cycle.

Your smog pump has nothing to do with it.

Light backfiring when cold also signals clogged or poor working fuel injectors. Have your injectors cleaned.

I wouldn't expect the oil change to do a whole lot, unless you had a sticky lifter from bad oil, if you are backfiring through the intake, and an oil change fixed the problem, I'd be suspect of a sticking valve.

In addition, you may want to note, backfiring puts added stress on your head gaskets, and can deystroy your catallitic converters.

"poopstang", yes I go to bithlo allot and yes I have neons "everywhere" as people say. Mid 13's...that's tight. I'm working slowly but surely on my mods. Next week I'm getting a shifter...bout time! Well, next time you see me there, holler, cause I'm not quite sure who you are. later

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Blueneonman - '95 5.0L Mustang GT Convertible | K&N Custom Cold Air Intake | FMS 9mm Wires | Hollow Cats | Flowmaster 2 Chambers | BBK Subframes | 6-pt Rollcage | 14deg Timing | King Cobra Clutch | FMS Adjustable Clutch Cable | Coolest Neon Lighting on a Mustang EVER!

Homepage: http://www16.brinkster.com/blueneonman/

Best time: 14.578 @96.20mph

unit5303:

You've brought up some interesting question I have now since you say my o/r hpipe is causing problems.

Could you explain what open loop and closed loop mean when you were talking about, "Your O2 sensor's don't work when your car is cold, you run in open loop, but my guess is your computer is taking closed loop info and adjusting your open loop cycle."

When I first bought my car, I took it to Moble to get this FISK (fuel injection service cleaner)put into the vacuum lines. I don't know if that did anything. Had an oil change done a 1000 miles ago. Just ran an injector cleaner thought the gas lines at empty tank.

Also still getting poor gas mileage. (225 to the tank). Was it a smart choice to go with a o/r hpipe?

Thanks

P.S. Sorry for steeling the topic jetuomi! http://www.mustangworks.com/msgboard/smile.gif

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Green '94 GT conv. -- K&N filter charger, FMS 9mm wires, Accel hipo cap/rotor, 180* thermo, 14* timing, off road H-pipe in front of 2 chamber flow's, and still workin' on the rest!

My car does the exact same thing. It started after I installed the long tubes, pro chamber crossover, and cat-back, and removed the smog pump. My engine was stock at the time. I have since changed EVERYTHING on the top end of the engine and it still does this. I was thinking it was the O2 sensor that I had that was falling apart, but I swapped those out for new ones and it still does this.

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Too much to list. Best ET on the car so far with stock 2.73 gears - 13.73@102mph

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