Mechanics

STALLING MOTOR, CUTS OUT IF ELECTRICAL PROBLEM

2005 Saturn L300 • 89,000 miles

I've been trying to fix this for weeks. My wife's car (L81 V6) has been stalling after it reaches it's normal PEAK temperature, when the cooling fan comes on.
It cuts out, and usually won't restart for 10+ minutes of sitting.
Sounds like no spark at all.
I've been told it's one of the following:
Dirty/clogged/bad EGR valve
Faulty Throttle Body
Dirty/clogged/bad IAC valve
Bad Crank Position Sensor

So far, I've ruled out the IAC, because I've been informed it uses the throttle plate to control idle air with the electronic throttle.
The EGR valve, going by ALL DIAGRAMS I have found online, does not exist! It sure as heck isn't where it shows it, right atop the passenger side of the motor, behind the throttle body, next to a big plastic cube with vaccuum lines in and out.
Either way, in my own head I am ruling out the throttle body and EGR - because of the way it CUTS out, and won't attempt to fire at all for a while after. It really feels electrical.

On to the CPS. My local mechanic said he read online 22 comments on stalling with this motor, and 21 of 22 were faulty CPS. Apparently they say the heat of the motor oil is causing it to go faulty at a certain temp. And that sounds like my issue. He told me to remove it AFTER it stalls out, quickly rinse with cold water, reinstall and attempt to restart. I don't really like that option, as it has restarted RIGHT after stalling before, and I don't think it will guarantee a solid answer.

How likely is this the CPS causing it? Is there anything I haven't mentioned that could be the culprit? I was originally thinking overheating going by the 'hottest temp and it stalls' theory. But I watched on my OBDII reader the temp, even at the stall point, peaked @ 204F.

Any input would be much appreciated!
Thanks, -Doug
Avatar
Dpawl31
July 2, 2012.




The first things you listed will not cause stalling while driving. They will cause engine performance issues such as hesitation or rough idle, but not a failure to restart.

The crankshaft position sensor WILL do that and it is a very common problem on all car brands. There should be a stored diagnostic fault code in the Engine Computer. I'm surprised your mechanic didn't check for that. That's the first place to start. Many auto parts stores will read them for you for free.

Caradiodoc
Jul 2, 2012.
I have a bluetooth OBDII reader, and I have received the following, sorry I did not add that in before!

P0727 Engine Speed Input Circuit No Signal
P0700 Transmission Control System (MIL Request)

Tiny
Dpawl31
Jul 2, 2012.
The P700 just means there is a code in the Transmission Computer and it is telling the Engine Computer to turn on the Check Engine light. To read that actual code you need a scanner that can access the Transmission Computer.

The other code suggests an intermittent crankshaft sensor. That is the signal that tells the Engine computer engine speed and when a piston is reaching top dead center. The same code could be in the Transmission Computer too because it needs to know engine speed, among other things, to calculate shift points

Caradiodoc
Jul 2, 2012.
My friend is working on it now, while I am at work. They pulled the sensor and it had small metal fragments stuck to it.
He (knowing we have the new sensor in hand) cleaned it off, and lightly sanded the tip of the sensor. Reinstalled and drove around town. No issues. Idle seemed smoother, seemed like it had more power, and more EVEN power.

I suggested they let it sit in the driveway and run, till the cooling fan comes on at least twice. After the first fan coming on - it stalled out again.
They are swapping in the new sensor right now. Think it'll work?

Tiny
Dpawl31
Jul 2, 2012.
Fault codes never say to replace parts. They only indicate the circuit that needs further diagnosis. About 50 percent of the time the sensor in that circuit is the cause of the problem, however, given the consistent way yours fails, I'd say there's a 90 percent chance the sensor is the cause, a one percent chance it's the Engine Computer, and a 9 percent chance it's due to a corroded terminal in an electrical connector or a wire rubbed through and grounding out.

Caradiodoc
Jul 3, 2012.
Just to add to this one with a P0727 it is most likely a bad crank shaft sensor I replaced a ton of crank sensors on those with and without codes. They sometimes set transmission codes when they fail. If you had a scan tool that read live engine data when it stalled and didnt start your could have watched the engine rpms while cranking it if the rpms read 0 rpms bad crank shaft sensor. Thats only with the symptoms you have though.

Saturntech9
Jul 3, 2012.
A TON of 'em? : )
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Caradiodoc
Jul 3, 2012.
Yes cardiodoc a ton/alot of them : -) also the P0727 is the transmission code that the P0700 transmission codes present code is refering too. So the scan tool was reading the transmission codes. It just didnt set a engine code for the crank shaft postion sensor.I dont like the remove the crank shaft position soak it water and see if it works ethier. You test if its bad when it doesnt start with a multimeter really simple. Also with a scan tool like I said earlier.I would find a new guy to fix my car with suggestions like that one that can use a multimeter and scan tool to diagnose problems.

Saturntech9
Jul 3, 2012.
We cleaned off the old one (metal fragments) and lightly sanded the tip.
It started up and ran better, smoother idle better power. But it stalled again.

Dropped in the new one, I took it on a long grueling test drive last night, not one issue.

Thanks for the help guys. And yes, saturntech9 is right about the codes. Only TWICE upon stalling did I get codes, otherwise it was clear of codes, with at least 30-40 other stalls.

Now, can either of you tell my why the diagram of the EGR valve EVERYWHERE I look for this motor, says it's behind the throttle body right on top of the intake manifold? Because it's NOT THERE on my wifes car, or my friends. And I am not just 'missing it', it's legit not there. Thinking they moved it, or REMOVED it, for the final year of the motor? (05)

Tiny
Dpawl31
Jul 3, 2012.
The best way to verify it's not a clinker in yer thinker is to look at the vacuum hose routing diagram under the hood. If any change was made after production, typically for an emissions recall, there would have been a new sticker applied over the old one. Either way, it will show it if it's there.

Caradiodoc
Jul 3, 2012.

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