Reader Question: I have purchased a 1996 Mercury Grand Marquis. I have replaced vacuum hoses, air filter, fuel filter, cleaned O2 sensors, and general maintenance items.
Exhaust is black meaning it is running rich and the idle is fluctuating causing it to stall when it is in park, neutral and reverse. It rarely does it during normal driving conditions.
I also have “water” coming out the exhaust pipe when I first start it up. I have the distinct feeling that all of this is being caused by a single problem as everything is pointing to the idle/black exhaust as the symptoms of the problem.
The only code thrown out is the MAF sensor, but even that was cleaned and inspected for damage and appears to be fine except on start up which is when the code appears.
What possible problems could cause these symptoms?
I would want to test and replace the MAF sensor, since they can cause complaints like you have when they fail. Sometimes you can clean them; sometimes you have to replace them. Since you are getting a MAF sensor code, I would look harder into it.
I would clean the throttle body and idle control motor as well for maintenance; they can cause idle problems and might cause your rich exhaust smell and black exhaust.
You really need to have a hand scanner hooked up to your computer so you can see what the engine control computer is seeing and what it is doing to try to fix the problem.
You can hook up a voltmeter to the O2 sensor wire and make sure it is working properly and switching from rich to lean and not just a straight-line signal.