Hi All,
First of all, I am a complete beginner, so I apologize in advance.
I have a 2002 VW Gti 1.8t (337 Edition). There are a bunch of issues with this car, but I am extremely broke (hence trying to fix it myself) and I am just trying to get the thing up and running.
Initial Problems:
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Coolant Leak (Fixed) - slow coolant leak, found crack, replaced piece no problems for past 2 months since fix.
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Check Engine Light - has been on, codes read P0420 (Catalyst System Efficiency Below Threshold) and p0411 (Secondary Air Injection System Incorrect Flow Detected)
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Have noticed some decreased power, idles high to start and then drops once warm.
I replaced the downstream O2 sensor, upstream too difficult to remove. The codes and drop in power makes me think this is a bad catalytic converter. However
New Problems:
- Overheats after maybe 5-10 minutes of driving.
- When I open the coolant reservoir, I can hear the coolant start to bubble and the level rises as the cap is opened.
Ok, being a beginner, I figured this was bad catalytic converter -> can’t exhaust -> heat & pressure build up. So, I googled a bit and saw I could test it with a vacuum gauge.
I hooked the vacuum gauge up to the port just behind the throttle body before the intake manifold (see pictures here). I was fully expecting to see the level slowly drop indicating an exhaust restriction. However, even at idle the pressure is on the high end (though I do notice it’s not at zero even when not hooked up). Then when I bring the RPMs up to ~2000 the vacuum increases and stays constant at about 25 inHg.
So I am officially stumped. Could I be hooking up the vacuum gauge incorrectly? Any ideas would be appreciated.
Final note: I do also see the needle vibrating quickly indicating worn valves. But I really am not looking for performance, just for it to last maybe another few thousand miles before I can either replace it or get it fixed properly.
tl;dr - Check engine codes imply bad catalytic converter. Car now overheating. Vacuum gauge shows an increase in vacuum when revved, but no slow decrease.