Stalls while slowing to a stop

'01 Tahoe with 213K miles. Dies when slowing to a stop, but only while the engine is warming up.

At cold start, the engine is fine and I can drive out of my neighborhood (stopping at 3 different stop signs along the way). Then I can make it half a mile down the street where it will die when I stop at the next stop sign. The tachometer drops below 500 then the engine quits. At this point, the coolant temp gauge is in the 180 range. Most of the time it will start right back up, but sometimes I have to give it throttle to keep it from dying.

Once the engine gets to running temp at just below the 210 mark, it runs with no problems.

I have cleaned the throttle body and MAF sensor. I have replaced the spark plugs and the wires. EGR valve is new and alternator is new.

Get any codes?

Where I would start:


Codes

Fuel trims

Fuel pressure

Check upstream oxygen sensors

Have you checked for vaccum leaks?

Steve Lam said:

'01 Tahoe with 213K miles. Dies when slowing to a stop, but only while the engine is warming up.

At cold start, the engine is fine and I can drive out of my neighborhood (stopping at 3 different stop signs along the way). Then I can make it half a mile down the street where it will die when I stop at the next stop sign. The tachometer drops below 500 then the engine quits. At this point, the coolant temp gauge is in the 180 range. Most of the time it will start right back up, but sometimes I have to give it throttle to keep it from dying.

Once the engine gets to running temp at just below the 210 mark, it runs with no problems.

I have cleaned the throttle body and MAF sensor. I have replaced the spark plugs and the wires. EGR valve is new and alternator is new.

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Put the truck in neutral before you hit the stop sign and if the truck does not die it could be a symptom your transmision on going out.

No codes.

I have put it in neutral while slowing and it didn't make a difference, so I don't think it's the transmission.

I'll see if I can capture the metrics on fuel and o2 sensors. I have not checked for vacuum leaks.

In my experience, that was usually caused by a vacuum leak.

swathdiver said:

In my experience, that was usually caused by a vacuum leak.

Click to expand...

I'm with James it maybe a vacuum leak. The brake booster works off vacuum, something to look at. Keep us posted

Sorry for the slow response - I had a work project consume all my free time.

I tried to check for a vacuum leak using propane and listening for a change in idle, but could not detect a change. I'm going to try again while monitoring short term fuel trim to look for a reaction, but it may be a little while before I get to do this.

Simply eyeing L-T and S-T fuel trim, I was seeing L-T fuel trim stay at a constant +5% to +9% with bank 1 consistently +4% over bank 2. For some reason, I was not able to get fuel pressure from my app (Torque Pro). I'll try to graph these values next time I drive it around.

The driving is getting rougher. Now when the engine quits, it does not want to keep idle. The engine starts, revs up to normal then immediately dies unless I press on the pedal to keep it alive. I have to keep up this nursing of the engine until it reaches running temp at which point it behaves 98% of the time with seemingly random and rare shutdowns while idling at a stop light.

Thanks for all the help. It's much appreciated.

Just to add to what others have said, check your fuel pressure regulator? I've never been able to see fuel pressure off of torque pro BTW.

Thank you everyone. I replaced the intake manifold gaskets, throttle body gasket, egr valve gasket, and egr return gasket. Vacuum now holds steady instead of fluctuating radically. She's running like her old self.