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Dave Nova
Dave Nova, Buick Technician
Category: Buick
Satisfied Customers: 1808
Experience:  ASE Master Certification. GM World Class Certification
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01 LeSabre 3.8L Starts & dies. Then when you try to restart

Customer Question

01 LeSabre 3.8L Starts & dies. Then when you try to restart it it cranks and acts like the timing is off or something. It's like it's trying to start but it won't. I have 53psi fuel pressure and with the key on and the engine NOT running the security light stay on steady. When it starts and runs for a few seconds the security light goes out when the oil light goes out. There was a fault code for the EGR stuck open, so I removed the EGR valve and it looks like a fairly recent replacement and it WAS NOT stuck open and had no debris wedged in the plunger. When it does run for a few seconds it emits a rather potent rotten egg smell out the exhaust pipe. I have no clue where to go from here. My diagnostic tools consist of a test light, a DVOM, fuel pressure gauge, and a read only scan tool.
Submitted: 1 year ago.
Category: Buick
Expert:  Dave Nova replied 1 year ago.

Try unplugging the mass airflow sensor, then start the engine. Does it stay running?

Customer: replied 1 year ago.

It does not start with the mass airflow sensor unplugged.

Expert:  Dave Nova replied 1 year ago.

Pull the vacuum hose from the vacuum port on the fuel pressure regulator. Is there fuel coming out of the vacuum port?

Customer: replied 1 year ago.

Already checked that...there is no fuel coming out the vacuum port.

Expert:  Dave Nova replied 1 year ago.

Does holding the throttle open allow the engine to run any longer after starting?

Customer: replied 1 year ago.

Nope.

Expert:  Dave Nova replied 1 year ago.

Have you tried loosening exhaust pipe from the rear manifold connection? If catalytic converter is restricted, taking the pipe loose at the engine will allow the engine to stay running.

Customer: replied 1 year ago.

You know what? I have a backpressure gauge that screws into the oxygen sensor hole. I check it that way. Let you know what I find.

Expert:  Dave Nova replied 1 year ago.

Sounds good. Sometimes just removing the O2 sensor relieves enough pressure to allow the engine to run.

Customer: replied 1 year ago.

Well now, this is curious. I had to clear it like it was flooded to get it to start with the O2 sensor removed and the backpressure gauge on but it started and stayed running with zero backpressure at idle. Even accelerating it was under a pound. Do I have a bad O2 that's not throwing a code?

Expert:  Dave Nova replied 1 year ago.

It is possible. If the sensor is biased lean (low voltage), it would fool the computer into commanding additional fuel to flood the engine.

Customer: replied 1 year ago.

I'll replace it and let you know what happens.

Expert:  Dave Nova replied 1 year ago.

Okay, I will look forward to your response.

Dave

Customer: replied 1 year ago.

Update: After tying up some other loose ends I decided to try it again. It started right up without manipulating the throttle so I left it idle until the thermostat opened. It now idles smooth and accelerates normally with no load on the engine. I'll try it in the morning and see what I've got.

Expert:  Dave Nova replied 1 year ago.

Now that the engine does start and run, are any trouble codes setting in the computer?

Customer: replied 1 year ago.

It's been a long day. I finally got back to it. When I first started it, it idled fine but had poor throttle take up like there was a dead spot in the TPS. After warming up for a minute or so that went away so I took it for a drive. I got about a mile and a half down the road before I went around a corner and it unceremoniously quit. The engine just died. No sputtering or coughing or lurching. It just died. I popped it into neutral while coasting and it started back up but when I put it in gear it bucked and popped and sputtered and died again. Still coasting, I repeated the process and got it back in the parking lot where I barely got it back into a parking space. The only time any warning lights, including the MIL, came on is when the engine died. I have a P0131 code PENDING for the new O2 sensor I just put in. The O2 monitor is not set.

Expert:  Dave Nova replied 1 year ago.

Will the engine restart now?

Customer: replied 1 year ago.

It sat all day Sunday. This morning it started and idled, but when I stepped on the gas it didn't accelerate. It idled for a few seconds with my foot off the gas and then died and didn't want to start back up. It would crank, but not start.

Expert:  Dave Nova replied 1 year ago.

How much fuel pressure do you have with the key on, engine off ?

Customer: replied 1 year ago.

53psi. It's in my original post before I changed the O2 sensor and it wouldn't run at all.

Expert:  Dave Nova replied 1 year ago.

With a plug wire removed at the coil packs, do you get a good solid spark while cranking?

Customer: replied 1 year ago.

I'm going to have to come back to this later today. Probably after lunch.

Expert:  Dave Nova replied 1 year ago.

That will be fine, just let me know.

Customer: replied 1 year ago.

Okay, I'm back on it this morning. It starts and idles. But doesn't accelerate. There is a very loud sucking sound coming from the air cleaner assembly, which I'm used to hearing for a few seconds on startup on the 3.8L. But this seems excessive. I have a very bright, crisp blue spark at the coil when I pull a plug wire off with the engine idling. It easily jumps across a gap over an inch.

Expert:  Dave Nova replied 1 year ago.

After running a while, does the engine still stall?

Customer: replied 1 year ago.

Yes

Expert:  Dave Nova replied 1 year ago.

AFter stalling, will it restart? If not, check for spark at that time.

Customer: replied 1 year ago.

It misfires and stumbles but will not restart. It has spark. I put my fuel pressure gauge back on to see if fuel pressure is going away. After putting gauge on it started back up. I'm letting it run until it dies again to see what happens to fuel pressure. I currently have 46psi idling.

Customer: replied 1 year ago.

Okay. I ran it again until it died with a fuel pressure gauge on it. It maintains fuel pressure idling and when it dies the pressure jumps up to 56psi. So I'm not having a fuel pressure problem.

Expert:  Dave Nova replied 1 year ago.

Wondering if it is a spark timing issue due to crank sensor or ignition control module heating up and malfunctioning.

Customer: replied 1 year ago.
Relist: Answer quality.
The "expert" "wonders" if the problem is one thing or another. I already "wonder" what the problem is. That's why I'm asking an expert. I can throw parts at the problem all by myself. I need to KNOW what's wrong with this vehicle.

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