2002 Lesabre randomly shuts off while driving - no codes (to cause this)

[dadymurano]

I have a 2002 LeSabre. It will shut off and you have to press the gas pedal to get it to start. It will not idle when this happens and with the gas pedal pressed it revs up and surges up and down while in neutral/park but will die if you don't keep your foot on the gas. I can drive it back home by keeping the gas pedal pressed while using the brake.
No codes to speak of - po401 and an occasional po440. Those codes have been coming on for a long time - 2 years. The car has 180,000 miles. Well maintained.
I checked the fuel pressure and it was 50psi, but the car was doing fine that day. - by the way, when this happens you can disconnect the maf sensor but the problem persists, no change in starting or running. Removed the EGR valve and cleaned it well. It was not vey dirty. Because it seemed like it was the gas shutting off I replaced the fuel pump. I replaced the MAF sensor.

I have replaced crank sensors on other cars that throw a code indicating it is bad. Same with cam sensor.

I just bought a fuel filter to put on but don't really think that is the problem. I may change the tps just to eliminate that. I hate throwing parts at a car without a sound reason for doing so. I think it isn't electrical related. I was sure replacing the fuel pump was the fix, until it wasn't.
All I have to work with is a cheap code reader. It's hard to see live data due to the small readout. If I can get my laptop to work on this car I'll be able to do more live data reading.

I'm somewhat frustrated at the moment.

 

[Mad_Coachman]

Sounds like EVAP issues. Possible faulty purge valve. If you're lucky it might be the purge valve at the front left of the engine. If you're unlucky you may have a vent valve issue. Look up code P0440 and go from there.

My brother had similar starting issues with his '09 Impala. It turned out to be his purge solenoid.

 

[dadymurano]

Does a bad crankshaft sensor throw a code? Does a bad tps throw a code? Oh and the exhaust seems to flow fine. I do not suspect a clogged cat. Nor do I suspect an ignition switch issue. The symptoms seem to indicate a fuel delivery issue that may be associated with a sensor input.

Can go for a day without issue or start acting up as soon as the car enters closed loop function.

Does a bad crankshaft sensor throw a code? - Hate to change it without good reason.

 

[dadymurano]

Checked for vacuum leaks, but was pretty sure I'd not find any and didn't. I't not be so intermittent if i had a vacuum leak. Unplugged the purge valve and it had no effect. It's running fine at the moment just idling in the drive. The iat shows the proper temp. I can unplug all the sensors on the intake - iat, maf, map, egr, evap sensor, tps, and it continues to idle fine. Obviously it will not rev up properly with all the sensors unplugged but it will start right up and idle.

Left the fuel gauge connected for 45min with the engine off with no leak down in pressure. Went from 50psi to 49.8psi over that time period. I see no reason to check the gas flow specks. The pressure gauge stays steady at 50psi when revving the engine.

I'm gonna find my old laptop with the diagnostic program and elm connector so I can drive it around while monitoring live data. It's that or throw more parts at it trying to guess at the issue.

 

[Mad_Coachman]

CPS doesn't throw a code, TPS will. Focus on P0440 (EVAP) and P0401 (EGR).
Start with your gas cap. 😉

 

[dadymurano]

Focus on P0440 (EVAP) and P0401 (EGR).
Start with your gas cap. 😉

I occasionally get the msg my gas cap is loose. I'm pretty sure i need a new one.

Those two codes have never caused my car to shut off, restart very hard and barely let me coax the car home or to the nearest parking lot. In the past they made no difference in how the car ran at all.

I'm pretty sure I have a more severe problem that has crept up on my 3800. If the crank sensor doesn't set a code I may replace that sensor. On another vehicle of mine I got a CPS and Speed sensor code when the crank sensor or cam sensor malfunctioned. The vehicle shut itself down and or entered limp mode.

But if the 2002 LeSabre w/3800 doesn't have a code set when one of those sensors malfunction I guess the only thing to do is throw those parts at it and hope that's the issue.

When I had a bad coil i got a po30x that told me the exact cylinder malfunctioning. Same thing when I let a spark plug wire melt to the exhaust manifold. Both were very easy to fix due to the code each initiated.

 

[Mad_Coachman]

Not sure what those photos have to do with your issues besides showing the fuel pressure. When you replaced the fuel pump did the new pump come complete with a pressure sensor or did you have to use the sensor from your original pump? What brand of pump?

 

[dadymurano]

Not sure what those photos have to do with your issues

The pictures are just the work I've done since i first got the car many miles ago.. The one picture shows where i replaced the intake manifold with aluminum water elbows, new MAP/speed density sensor, evap switch new plugs and wires. --- Did great for a long time.

When you replaced the fuel pump did the new pump come complete with a pressure sensor or did you have to use the sensor from your original pump? What brand of pump?

I bought a new pressure regulator that goes on the fuel rail. Got the fuel pump/module from rock auto. It is doing fine. The one time the car shut off the pressure guage still said 50psi.

Today I just received a crank position sensor - AC Delco Gold along with a cam position sensor, also AC Delco Gold. I don't buy junk.


The car has run prefect with an occasional po401 and the dash msg to check my gas cap. This has never affected my car/engines performance.

It's my hope that an intermittently bad crank and or cam sensor can cause my problem even though there are no codes.
I'm going to change them both. If that corrects my issue I will not know which one was intermittently defective. I'm OK with that as long as the engine quits dying and running like shit.

I've moved on past a fuel pump or fuel regulator issue. I suppose an intermittently bad injector could be an issue. But a fuel injector stuck open should cause poor fuel psi and very rich with a po30x associated with the cylinder it feeds.

I'll update after replacing the cam and crank sensors. It's a somewhat perplexing issue.

 

[dadymurano]

One more thing I thought may cause this issue is a defective (intermittently) TPS switch. From my understanding they usually throw a code.
I still am using a chep obd meter but will try to drag out my laptop with OBDWiz, Forscan, and a couple other programs so I can read several pids at one time. This could help narrow down the issue.

This is a very nice car for it's age. The 3800 is a very good engine. I'll not give up on it until I correct this problem.

I'll update this thread with what I believe fixed it and what indications led me to the correct diagnosis. I do wish I had ordered a TPS along with the cam and crank sensors, but have been told they throw a code and even with my cheap obd2 meter i think the TPS showed 0% at idle and 10-20% as i pressed the gas pedal, but it could be intermittent. Wish it would do it all the time. Would be easier to find i think.

Any ideas are appreciated. Would love for someone to say they know exactly what's wrong and why.

 

[Homer Jay]

Although you replaced the MAF sensor, disconnect it and see if there's a change.

 

[Mad_Coachman]

I still say you should focus on addressing the EVAP issues. Since you mention having to put out foot to the floor that puts it into "clear flood" mode which turns off the injectors. You may have one or two leaky injectors. Another scenario points more to the EVAP issue with regard to proper gas tank venting. This is why I asked about what brand of fuel pump did you use and if it came with a new pressure sensor. Some cheap pumps come with no sensor so you have to use your original. I doubt that the TPS or crank or cam sensors are at fault. What brand of pump?

 

[dadymurano]

FAERSI Fuel Pump. Comes with a new pressure sensor. Made by the same manufacturer that makes Delphi / AC Delco.

 

[dadymurano]

Although you replaced the MAF sensor, disconnect it and see if there's a change.

Doesn't seem to make a difference. Keep in mind it doesn't do it all the time I will have more time to work on it this weekend. It is not my daily driver.

I rarely get the po440 code. My understanding is this should not cause the car to shut off and become barely drivable. I smell no gas fumes.

 

[Mad_Coachman]

FAERSI Fuel Pump. Comes with a new pressure sensor. Made by the same manufacturer that makes Delphi / AC Delco.

Never heard of it.

 

[2007LucerneCXL]

When it happens do the dash lights flixer / go off momentarily or it just shuts down and dash lights come on? Has the ICM and harness been checked along with the ground wire? Any stored or pending codes other than the ones posted? Any record on vehicle operations and conditions when it cut out, looking for common occurrences like turning left, morning, 1/2 tank of fuel etc. as there are the unusual things that may help on troubleshooting.

Once the replacement parts are installed those items might be something to consider checking if the problem comes back, but intermittent it could be any number of things.

 

[Homer Jay]

Doesn't seem to make a difference. Keep in mind it doesn't do it all the time I will have more time to work on it this weekend. It is not my daily driver.

I rarely get the po440 code. My understanding is this should not cause the car to shut off and become barely drivable. I smell no gas fumes.

Understood, it gets frustrating trying to fix an intermittent problem. I would suggest leaving the MAF disconnected when you use the car this weekend. The driveabilty issues you are experiencing could be attributed to a faulty MAF circuit. Good Luck!

 

[Mad_Coachman]

Some of the parts that you have replaced may be of questionable quality and may be compounding your issues. Where did you get the MAF from? Ebay? I ask these questions because no-name cheap Chinese knock offs can cause even more issues especially MAFs and EGR valves.
What brand was the MAF?

 

[imidazol97]

Reading again through all the posts, I still come up with the conclusion that diagnosis
is the key to fixing the problem. Hanging parts hit and miss along with buying the
cheaper, knockoff parts often adds problems.

Get a good code reader and scanner to get the exact code. Study the meanings of those
codes and troubleshoot those parts. A P040X code may indicate the symptom the
computer is noting, but the problem may be elsewhere in the emissions control.

I had a P040X, I don't remember the exact last number. I studied my copy of the FSM for that leSabre.
I replaced the vent cannister. I checked the hoses for cracks and leaks. It turned out the purge valve sitting
on the engine was the problem. It wasn't closing completely or opening completely. But replacing
it ( AC Delco version) fixed my light and gas cap message. It was a low cost fix, but I already
had replaced the vent cannister.

 

[Mad_Coachman]

A simple Google search shows this for the P0401:

P0401 Buick: Code Meaning, Causes, Symptoms, & Tech Notes

The Exhaust Gas Recirculation (EGR) valve is controlled by the Engine Control Module (ECM). The ECM controls the EGR valve by supplying a 12-volt pulse

www.engine-codes.com

 

[2007LucerneCXL]

Might as well use this.