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Random massive "vacuum leak"


white4d96

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Sometimes when I drive my car, particularly on cold starts, it will act like it has a massive vacuum leak: It will stumble and sputter, and if you look at the gas it will rev to 2500-3k and idle there for 30 seconds. Then it's fine. Thought it was my brake booster, pulled the line and plugged it, nothing. I don't hear any hissing or other noises that would indicate a vac leak. Am I just not looking hard enough, or is there something else I should be looking for?

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  • 2 weeks later...

I had a similar problem with my century a while ago.. it was so bad that it actually died a couple times. It turned out that it was the breather tube..the vac hose that goes from the intake to the back of the engine, had come off at the engine. After I put it back on, I started it up, and it sputtered for a second, but smoothed out, and has been fine since.

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Check the vacuum hose on the back of the engine for the EVAP purge solenoid.

 

It sounds like it's broken, so when the solenoid opens to pull vacuum on the fuel tank to run the diagnostic monitor, its just allowing more air into the intake.

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I will check all the hoses again.

 

I had my friend run his ETHOS on the car and TPS is good, so that's ruled out. Also found out my gauges are all off big time, but that's another issue.

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I had a similar problem with my century a while ago.. it was so bad that it actually died a couple times. It turned out that it was the breather tube..the vac hose that goes from the intake to the back of the engine, had come off at the engine. After I put it back on, I started it up, and it sputtered for a second, but smoothed out, and has been fine since.

 

You mean that plastic vacuum line that goes from the intake tube to the rear valve cover? I can't get mine to stay on the rear VC for some reason, although oddly enough it doesn't seem to affect anything. I'm seriously about to plug the tube and run a breather on the rear VC and see what happens.

 

I think on Friday I am going to try and replace most/all of my vac hoses and see where that leads me.

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My breather tube has a duct-taped crack on the PCV side... and for whatever reason won't stay seated in the rear valve cover side.

Considering the breather routes into a large hole in the intake I would have thought there would be a major vacuum leak similar to when I had the TB gasket upside down... yet it seems to make zero difference. Strangeness...

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Soooo I think I found the issue, maybe, or at least another issue: A bunch of my oil and coolant seem to have grown legs. I had a minor oil leak but it's gotten worse, and I just topped off coolant like six weeks ago and now the overflow's barely got anything in it when hot. LIM?

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Sounds like it could be a bad Idle air control sensor. You could get one try it out and return it if its not the issue. You might have to make the IAC relearn the car's idle. Google it.

 

If you gas it while it starts , does it still sputter, or not sputter until you let go of the gas pedal? If it still sputters while your foot is on the gas than it is not the IAC. The IAC controls the gas input automatically when u let go of the pedal.

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Okay, well in that case have you removed the battery or ECM for a long period of time recently before this problem arose. if that is the case, the IAC might need relearning. ok those are my ideas. Hope you get it fixed and driving flawlessly again!

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