Hi guys, I'm new to the forum.
Looking to see if I can get some help with my Impala stallling issue.

I have a 2000 Impala with a 3.4 liter engine. About 160K on the odometer.

A few weeks back my check engine light went on.
A day after it went on, my car stalled on me on my drive home.
It started right up no problem and I continued to drive it for the next couple of days without it stalling.

I continued to drive the car the next few days with the check engine light on,
As the days went by, the car started to stall two or three times a day at stops or deceleration.
The more tijme passed the worst the problem got.
It got so that the car now is stalling every few blocks I drive and now even stalls while accelerating or going at a steady speed, doe'snt have to be at a stop. Its stalling now whether the car is in park or I'm driving it.

Sometimes it will start right up, and sometimes I have to crank it several times before it re-starts.

Anyways, I scanned the car with a cheap code scanner I borrowed from a friend.
Code P0401 turned up (unsufficient EGR flow)

I took the EGR valve off as well as the throttle body linkage and cleaned the port where the EGR valve attaches to and goes into the intake manifold. The port was completely clogged.
I cleaned it thoroughly using carb cleaner and a coat hanger.
Thought that would cure my stalling problem but it did'nt.
Btw, I installed a new gasket when I took out the throttle body and also cleaned the IAC valve with a sensor safe cleaning spray.

Car is still stalling every few blocks.

I cleared the PCM of any codes and I have'nt been able to drive it long enough to see if the same code resets because it stalls to frequently for any codes to set.

I replaced my EGR valve with a new one, it still stalls.

I've also replaced the fuel filter and ran a fuel pressure test and determined that the fuel pump is good. The car starts right up, reads right above 50 psi and when it stalls the fuel pressure does not drop. It stays steady at the same pressure reading it was on when the engine was runnning.

I also purchased an entire ignition module with the three coil packs from a junkyard, replaced it and still the car stalls as before.

I've read on several sites that a crankshaft position sensor is a common problem with cars stalling.
I replaced the one behind the harmonic balancer as it was leaking oil from the crankshaft area. I replaced the oil seal there and the crankshaft sensor as well .
Car is still stalling.

Let me sum it up. This is what I've replaced.

EGR valve
Ignition module and coil packs
Fuel filter
Crankshaft sensor behind harmonic balancer.
Spark plugs (the spark plug cables look fine)
I've also checked all the vacuum lines and they look fine. I dont see or hear any air leaks.

I've also took a map sensor from a friends 3.4 engine and put in my car and I still had the stalling issue. I put my old MAP sensor back on.

Anyways, the 2000 Impala has a 2nd crankshaft sensor that wires lead to the ignition module. I have'nt replaced it but tested that sensor and it reads within specification.

I'm at my wit'* end and dont know what else to check.




Btw, with the old EGR valve and the new one I installed, I performed the 9 volt battery test to get the valve to open up and see if its working properly. Both the old and the new valve open, but my Impala does not idle rough or pretends to stall when I apply the 9 volts and the valve opens.
I'm wondering why this is and if this has something to do with my stalling problem.

The throttle body port hole is not clogged, I cleaned that, so I would think that when the EGR valve opens when I apply the 9 volts, my engine idle rpm should drop, but it remains steady, and as long as the car is idling, it idles smooth.
It does'nt idle rough or drive or accelerate rough for that matter.

I



One last thing. A few of the times I try to restart it, it will act like its going to die and idle rough for few seconds like its starving for fuel, and then shut off. I'll crank it again and it will start right up with a smooth idle until it completely stalls again after a few minutes of idling smooth.

Any suggestions would greatly be appreciated.

Have you checked the throttle position sensor?

There'* also the breather tube..the vacuum line that goes from the intake to the back of the motor, that might have come out of the cylinder head. I had that happen to me, and it caused a weird idle.

Typically the insufficient flow is a map sensor issue. The map reads the change in pressure as expected when the egr opens. I'd want to see it changing on a scanner as the egr opens. Plus EGR only opens during cruise etc for fuel mileage.

There is only one crankshaft sensor behind the balancer. No other crank sensor exists. There is a cam sensor, but taht won't make you stall.

I have'nt tested the TPS as I'm not getting a low or increased idle rpm.
The car idle'* fine, it just cuts off at random as if you shut the key off yourself. It doe'snt stutter or hesitate when it stalls.

As I stated earlier, a few times I've tried to start the car and usually when its been sitting overnight and on the first start of the day, upon turning the key the engine will start and act rough as if its starving for fuel. If I let the engine idle without stepping on the accelerator pedal, the engine will stall after a few seconds.
If I step on the accelerator, the engine rpm will increase slightly and if I leave my foot on the accelerator pedal after about 15 seconds the engine will either stall or it might go to reving normally and return to a steady idle as if the car is fine.
Usually for the car to act starving for fuel for a few seconds, it will have to sit with the engine off for a few hours.
If I turn the engine off and try to restart it again, the car will most likely start and idle normally before it stalls again after a minute or so.

Btw, I have'nt noticed any episodes of the engine acting like its starving for fuel when the engine has been warmed.

Now that I think about it, since I've gotten the engine to idle normally and smoothly by pressing on the accelerator pedal and waiting those few seconds for the engine to clear itself and idle normally, maybe the TPS could be the cause of the stalling.
I'll check to see how to test the TPS and let you know my findings.

.....I have checked the breather tube you talk about and looks fine. Even ran my hand all the way through it as the engine was idlling to check if it was leaking or sucking air.

The Impala 3.4 liter has 2 crankshaft sensors. A 24X sensor located behind the crankshaft balancer, and a 7X sensor located on the side of the engine block which I have tested and reads within specs. Though since my stalling is an intermittent problem, the engine stalls at random, I wonder if the crankshaft sensor on the engine block is failing intermittently and reads fine when I test it.

The MAP sensor I took from a friends 3.4 liter engine and installed on mine but I still got the same stallinig issue with his MAP sensor installed.
So I think I eliminated the MAP sensor being the problem.

Just checked the TPS 2K.

I disconnected the wiring harness from the TPS, put the ohmeter on the 20K scale and probed two the leads.
The ohmeter read 1.3 sitting at rest, then I moved the throttle up slowly to see it change readings smoothly throughout.

The readings changes smoothly no rough or bad open spots.
The reading at rest was 1.3 and the TPS reading fully open read 4.25.

From what I understand, if I had a bad TPS, I would have had erratic readings as I moved the throttle linkage.

Moved to Chevrolet maintenance and mechanical section.

the crankshaft pos sensor on the block would be my guess, those intermittent problems are hard top track down by testing like you say it tests fine but it runs fine sometimes to so you really dont know. the only reason i say i would just replace it is because i had the same random stalling and running fine sometimes on my old 3.1 gp and thats what it was

Yeah, I may just go ahead and replace that 2nd crank sensor, but before I do I have a question to anyone that may no the answer to it.
I cleaned out the port hole that had been clogged to goes from where you assemble the egr on the intake manifold to inside the intake manifold itself.
When I manually command the egr pintle open using a 9 volt battery, the intake manifold is supposed to suck in exhaust air and stall or at least make my engine stutter. But when I apply 9 volts to the EGR, I can hear the pintle opening, but the engine remains steady and wont stutter or stall.
I'm thinking this has got to have something with the stalling issues I'm having.

Why is'nt my engine stalling when I'm actually commanding the EGR open using a 9 volt battery??????

I have'nt just yet purchased that 2nd crankshaft sensor as I'm trying to refrain from just throwing parts at it.
Before I do, does anyone have any thoughts on me needing several crank attempts to start the engine.

Its hard to start, and when its cold it idles rough for several seconds before it smooths out by me leaving my foot on the gas pedal.
Another thing I've noticed is that I need more cranking attempts to start the engine if I just turn the key.
......but if I step on the gas pedal some, one or two attempts will start the engine.