Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!
2005 mazda tribute v6 3.0 liter intermittent stalling at stops
Cleaned the throttle body and did a idle relearn, the car still has a an erratic idle and stalls at stops, fuel trims are good no vacuum leaks and no codes, I decided to change the pcv valve because it was past due for "maintenance", and the car is fixed no more stalling. My question is how can you test a faulty pcv valve??? I did the shake test and it rattled like it suppose to
You can pinch the hose going to the pcv valve and look for a rpm change, You should have an rpm drop like 80 or so.
Normal fuel trims with the stuck open pcv valve? I would have thought that the fuel trim would be positive with the vacuum leak creating by the pcv valve
I've been there before on that engine. Erratic idle, normal trims, functioning IAC, no external vacuum leaks. Really had me scratching my head for awhile. I eventually did what Monde suggested and pinched off the vacuum PCV hose. Smoothed the idle out right away.
Beyond just pinching off hoses, how could you test for that? Only thing that comes to mind would be to measure crankcase pressure with a manometer or vacuum gauge. With a leaking PCV valve, you'll see excessive crankcase vacuum. Anything more than 2-3 inH2O would be suspect.
the issue with that is the hose that connects to the pcv valve is hard plastic and with quick disconnects at the end of them, but i do understand the steps of how to test it now... thank you guys
Only thing that comes to mind would be to measure crankcase pressure with a manometer or vacuum gauge. With a leaking PCV valve, you'll see excessive crankcase vacuum. Anything more than 2-3 inH2O would be suspect.
Had the chance to test this out earlier this week, on this 3.0L engine. Two bad PCV valves, both causing a high idle. One had 1.8 inHg in the crankcase, the other had 1.1 inHg. Or about 30 inH2O and 17 inH2O.
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