2002 Bonneville Stalling a lot, idles low

[soggytoast]

I've been having this problem since early December or so. Car has been serviced multiple times and I always tell them to look into this issue, but for some reason they say they didn't see any problem.

What happens is I turn the key to the ignition and it cranks:
*Sometimes it just cranks and cranks and doesn't start.
*If I stop and turn it again I'll hear a pop sometimes (misfire)
*Sometimes the engine will catch but quickly die out
*If I hear it begin to start and give it some gas I can get it to idle and then it's drivable.
*Before it gets to idle, the engine will rev up and down a little, like it's going to die out but just barely makes it to idle

*Sometimes it stalls if I'm stopped at a light or coasting on the highway (although kind of rare).
*In a few very rare instances it idled really high. Like I felt like I would be accelerating if I let my foot off the brake.

Not sure if this is related, but sometimes if I lightly tap the brake while it's starting, I can feel something churning under the break pedal. This one's kind of scary.

I posted on here before and most recommended that the throttle body be cleaned. I cleaned it a few weeks ago and didn't seem to fix anything. I was expecting thick black gobs on there, but it was relatively clean.

I want to look into the MAF sensor because that seems relatively easy. I heard you can just disconnect it and try to run the car without it to see if it's faulty... is that true?

Also I read that the crankshaft sensor might be an issue. Is there any easy way to test that theory?

[2kg4u]

Disconnect the MAF sensor and start the car. If it idles okay, replace the MAF sensor. If the engine is catching at all, the problem is not the CPS. A malfunctioning CPS will result in no spark at all.

[2kg4u]

You might want to test the throttle position sensor:

http://www.pontiacbonnevilleclub.com/fo ... c9098.html

[soggytoast]

Disconnect the MAF sensor and start the car. If it idles okay, replace the MAF sensor. If the engine is catching at all, the problem is not the CPS. A malfunctioning CPS will result in no spark at all.

Okay, so I disconnected the MAF and tried to start the car.

It seemed like it was easier to start, but I'm not really sure if it actually made a difference because the stall outs aren't totally consistent.

I do notice that once I'm started and idling, it starts at about 1,000 RPM, then slowly dips down to about 650 RPM over the next 30 seconds or so. This happens both with the MAF sensor connected and disconnected. Also, when I'm coasting or stopped at a light, randomly the RPM will dip a little for just a fraction of a second before rebounding. And obviously if it dips too much, that's when my stall out happens.

[soggytoast]

After some more thought and research, I think the problem might be bad vacuum hoses. So I saw you can buy a can of carb cleaner and start spraying around to see if you can identify the leak. Maybe I'll try it this weekend...

[00Beast]

Definitely sounds like a vacuum leak. Have you checked the PCV valve under the MAP sensor on the passenger's side of the intake plenum? If the o-rings aren't properly installed on it, it can cause all kinds of weird issues.

[soggytoast]

Definitely sounds like a vacuum leak. Have you checked the PCV valve under the MAP sensor on the passenger's side of the intake plenum? If the o-rings aren't properly installed on it, it can cause all kinds of weird issues.

So this afternoon I sprayed the whole thing down with carb cleaner. Used an entire can. The engine didn't even flinch. I don't think it's a vacuum leak