stall problem

[kitchen sink]

hello. just a simple question. iv'e been working on a stall problem with the wifes grand prix. ( a 2000, 3800, GT ) is there such a thing as a fuel pressure regulator sensor ? a buddy at work told me this was the problem, but, i'm not sure if this sensor is actually real. iv'e already changed the fuel pump, and have checked the iac & maf sensors. i have bought another ignition switch, but have not installed it yet. thanks in advance for any advise.

[tblake]

When it stalls out, do you get any warning lights? (IE "TRAC OFF")?

[CrazyHorst]

There is a mechanical regulator in the fuel rail assembly but this is not sensed or electrified.

It is attempting to provide ~60 psi differential between the fuel rail pressue and the intake manifold (typically in a vacuum condition).

Without further info likely suspects are carbon in the IAC port or the crank position sensor.

[kitchen sink]

no, there are no warning lights at all. car just shuts off. usually at a red light or stop sign. it might do it twice daily, or it might go 2 or 3 days with no problems. but, is there such a fuel pressure regulator sensor ? sorry crazyhorst. didn't see your post. could a crank sensor problem be intermittant?

[CrazyHorst]

The crank position is the reference for the ignition.

Thinking abstractly here...the rotational position of the crank which informs the PCM about when TDC is approaching and thus when to fire the ignition...more complex than that as the PCM makes other "decisions" based on other inputs, but without the base reference pulse the ignition may not fire at all...and so...the engine stalls.

I would think there are two possible failure modes for the crank sensor, either it could go completely DOA or it could start going intermittent before it finally dies.

The mechanical fuel rail regulator is fairly low on the tree in terms of probability IMHO...I've never replaced one in all the miles driven below...

I mentioned the IAC port as the IAC motor can function perfectly, but it is actively metering a passage (I call this a "controlled leak") around the big throttle blade. Even though the motor works and responds properly, if the passage is carboned up it won't be able to control idle right...might be OK in neutral or park but get flaky when it has to compensate for the additional load of turning the torque converter when in Drive.

[Mickey#1]

There's no fuel pressure sensor just a fuel tank pressure sensor for the EVAP system. Don't believe it can cause the engine to stall.

When does it stall? Hot? Cold? Idle? Cruising?
Does it restart easily after stalling?

[kitchen sink]

When does it stall? Hot? Cold? Idle? Cruising?
Does it restart easily after stalling?

it usually stalls at low idle, like at a red light or stop sign. at both, hot and cold temperatures. it usually restarts without a problem.

[Mickey#1]

MAF sensor is another possibility. A friend had that problem on a 2000 Bonneville. We scanned the MAF frequency & found it out of spec. It's an expensive part that you don't want to replace without confirming it's bad.

Give me a few minutes & I'll post a video of what her car sounded like.

Here's the video - sometimes it would stumble (almost stall but correct itself) & other times it would stall.

[tblake]

He could unplug the MAF and drive it like that for a week. See if the problem still occurs. With the MAF unplugged, idle will be a little loopy, you'll get and SES light, and you might lose a MPG or 2.

Crazyhorst I think has a good idea with the Crank Position Sensor. Only thing that doesnt make sense is that when a 3800 stalls out due to a flaky CPS, it will almost always turn the "TRAC OFF" light on.....

I'm not for sure on this one. The CPS is a fairly cheap part compared to the MAF. If your car has over about 80,000 its probably due for a new CPS. Mine failed right at 80,000. Same deal, stalled, restarted, but my TCS off light litup so I knew right away what it was.

[kitchen sink]

Thanks for all your help. i will change the cps next weekend.