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2000 Impala stalling issues
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divac
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Oct 12, 2011, 8:11 PM
Post #1 of 16
(10178 views)
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2000 Impala stalling issues
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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's 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.
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Old 396
User
Oct 13, 2011, 11:01 AM
Post #2 of 16
(10144 views)
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Re: 2000 Impala stalling issues
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Drive with an engine vacuum pressure tester attached to a good engine vacuum source and post the results.
If possible post the "Live Data".
Disassemble the throttle body and throughly clean each part in a parts cleaner, and put it all back together with new gaskets. Don't use any of the old gaskets.
Rule out a catalytic restricted converter. Post the results of an exhaust back-pressure test.
Make sure the EGR getting the command on signal from the PCM.
Confirm an operational MAP sensor.
Confirm an operational PCV valve and PCV system.
(This post was edited by Old 396 on Oct 13, 2011, 11:09 AM)
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Hammer Time
Ultimate Carjunky
/ Moderator
Oct 13, 2011, 4:49 PM
Post #4 of 16
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Re: 2000 Impala stalling issues
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That should have a 3 solenoid valve and unless you are triggering all 3 simultaneously, you are only getting a partial opening but you should still notice a change in the idle, not necessarily stall though.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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divac
User
Oct 13, 2011, 6:22 PM
Post #5 of 16
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Re: 2000 Impala stalling issues
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The EGR valve has five pins. I found out about the 9 volt battery test on youtube.
On the youtube video I believe it was a similar valve with various pins, and the guy protruded the two outer pins with the 9 volt battery and the engine just about stalled.
When I do the same to my egr valve, I hear the pintle opening on the egr, but there is'nt any change at all to the idle rpm.
On a 5 pin EGR valve, how would I go about manually triggering all three solenoid valves as you suggest?
(This post was edited by divac on Oct 13, 2011, 6:23 PM)
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Hammer Time
Ultimate Carjunky
/ Moderator
Oct 13, 2011, 6:27 PM
Post #6 of 16
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Re: 2000 Impala stalling issues
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You can't do that with a 9 volt battery. There are 3 separate trigger wires for the 3 different solenoids.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Blulakr
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Oct 13, 2011, 8:16 PM
Post #8 of 16
(10107 views)
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Re: 2000 Impala stalling issues
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EGR not opening will not cause a stall, egr not closing will. You can check this by removing the valve and visually verifying the pintles are closed. reinstall the valve and leave it unplugged. If the car idles ok then reconnect the valve. if the stalling reoccurs then the valve may be sticking open. Not likely though.
Make sure throttle body is clean. Disconnect battery for 30 minutes and reconnect to enable idle speed relearn.
Can you prevent it from stalling by holding your foot on the throttle a little at stops?? If so suspect faulty IAC.
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Discretesignals
Ultimate Carjunky
/ Moderator
Oct 14, 2011, 4:40 AM
Post #10 of 16
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Re: 2000 Impala stalling issues
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There is another crank sensor in the engine block on the firewall side of the engine. There is a twister pair of wires (yellow and purple) from the ignition module. Check the wires and make sure they aren't chaffing. Sometimes they chaff on the side of the block or get burnt on the exhaust and cause stalling.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Oct 21, 2011, 6:35 AM
Post #12 of 16
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Re: 2000 Impala stalling issues
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They make a cool hand held vacuum pump (like a pistol) and gauge on it that isn't that expensive and a must IMO for pros or higher end DIYers. Will either just read vacuum or make some to test assorted vacuum operated devices anywhere in a vehicle,
T
(This post was edited by Tom Greenleaf on Oct 21, 2011, 6:38 AM)
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Discretesignals
Ultimate Carjunky
/ Moderator
Oct 21, 2011, 4:22 PM
Post #13 of 16
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Re: 2000 Impala stalling issues
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You can also check your grounds and move harness around under the engine bay to see if you could induce the stalling.
Intermittent MAF sensor could cause a stalling condition, but usually the PCM picks up on the MAF not sending a signal and will set a code. If it doesn't restart, you can unplug the MAF. If the engine restarts, you should monitor MAF sensor output. You'll need to measure frequency with a scope or graphing multimeter to see the signal.
I don't think an IAC valve would all the sudden cause the engine to stall after it has been idling. The IAC valve on that one is a stepper motor design. The IAC would have to be commanded closed by the PCM to kill the engine if it was sitting there idling and all the sudden stalled. If it was a Ford electromagnetic IAC valve, I would say yes that would be a possibility.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Oct 21, 2011, 4:25 PM)
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Discretesignals
Ultimate Carjunky
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Oct 22, 2011, 6:14 AM
Post #15 of 16
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Re: 2000 Impala stalling issues
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You pretty much eliminated the MAF and the IAC by leaving them disconnected while the engine was running as the stall still occurred.
You have fuel pressure when the engine stalls out, so it shouldn't have anything to do with the fuel delivery system.
That leaves the ignition system, the wiring/connectors, and the engine computer. The PCM would be the last thing on the list after all other things have been checked out and eliminated.
I'd check all ground connections, wiring, and connectors. Inspect your engine room harnesses for chaffing. Wiggle them around the see if you can induce the stall. Check around your bulk head connectors and connectors under the dash that run to the fuse panel. Unplug connectors and check for corroded pins. Get an electrical contact enhancer and clean your connector terminals.
If you can get hold of a high end scan tool, you could check other modules for stored codes, especially the BCM. Check the ignition switch circuits for excessive voltage drops while the engine is running and everything is turned on. You'll need a volt meter and wiring schematic. They had problems with ignition switched on those, so keep that in mind.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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divac
User
Feb 8, 2012, 8:13 PM
Post #16 of 16
(9634 views)
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Re: 2000 Impala stalling issues
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You pretty much eliminated the MAF and the IAC by leaving them disconnected while the engine was running as the stall still occurred.
You have fuel pressure when the engine stalls out, so it shouldn't have anything to do with the fuel delivery system.
That leaves the ignition system, the wiring/connectors, and the engine computer. The PCM would be the last thing on the list after all other things have been checked out and eliminated.
I'd check all ground connections, wiring, and connectors. Inspect your engine room harnesses for chaffing. Wiggle them around the see if you can induce the stall. Check around your bulk head connectors and connectors under the dash that run to the fuse panel. Unplug connectors and check for corroded pins. Get an electrical contact enhancer and clean your connector terminals.
If you can get hold of a high end scan tool, you could check other modules for stored codes, especially the BCM. Check the ignition switch circuits for excessive voltage drops while the engine is running and everything is turned on. You'll need a volt meter and wiring schematic. They had problems with ignition switched on those, so keep that in mind.
You were right about the ignition switch my friend!
Well, the Impala had been sitting nearly 4 months.
After thoroughly checking for different things that could cause the problem I got tired of seeing it sit there. I made up my mind to have it towed to a Chevy dealership for them to figure it out.
Taking it to a dealership is always an absolute last resort as I just dont trust they will be truthful with me when they diagnose it.
Anyhow, I decided to to one last check of all the fuses and probe them for voltage.
Doing this I found the problem.
I probed the fuse at the panel inside the Impala labeled "pcm/bcm/clstr" and found it to be reading much less than the battery voltage.
I was actually using a probe light, and when I probed that fuse the light on my probe lit very dim.
Every fuse on the fuse box panel lit bright, but the "pcm/bcm/clstr" did not.
Turning the key on the ignition switch on and off several times, I found that the circuit I was probing would light up proper (12 volts) in some instances.
When that circuit would read 12 volts the car would start right up.
Leaving the test probe in the circuit, the car would shut off after a few seconds and the circuit would simutaneously drop below 12 volts.
I then did a google search and found out that if the "pcm/bcm/clstr" circuit was reading below battery voltage, the probable cause would be a bad ignition switch.
I did'nt change the ignition switch however.
Instead I ran a wire from a good 12 volt source thats holds current only with the key positioned at on, and ran that wire to the "pcm/bcm/clstr" circuit, and presto problem solved.
My Impala is up and running with no problem.
I would never have thought that the ignition swith would be the problem because everything else in the car was working. I had probed for 12 volts at the ignition module and it was fine.
The only problem was that the care was stalling.
Turns out that because there is a wire coming from the ignition switch thats intermittently not holding proper voltage, the PCM and BCM were not getting the 12 volts from the ignition switch and causing the car to stall.
It took 4 months of seeing the car sit, but I can say I'm a happy man having fixed it myself.
Those con boys at the Chevy dealership can kiss my ass!  
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