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Engine RPM erratic and shutting off while driving

Tiny
DYLAN GILL
  • MEMBER
  • 2004 CHEVROLET IMPALA
  • 3.8L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 91,000 MILES
My car when first started will fluctuate rpms for about three minutes. It will moderately rev up to about 1500 and than down to below the idle which is about 650-700. The headlights on the vehicle will flicker when it does this.

Sometimes while driving the car will shut off, the battery light indicator pops up but no check engine light comes on.

Somethings to note, if I let car warm up for ten minutes or so there does not seem to be any issues after that time or at least I cannot get it to repeat. Every time this has happened it has been after letting the car sit overnight.

I took it into the Chevrolet dealer about two to three weeks ago and got my water pump replaced, they also replaced the serpentine belt.

I took it into the dealer again after this problem I am asking about came up. They told me they got a code for a bad MAF so they replaced that. They also checked my battery and it is good.

Wondering if you have any insight what this might be before I decide to go back again.

By the way, my car has a supercharger if that matters.
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Thursday, March 29th, 2018 AT 10:02 PM

26 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 48,363 POSTS
Yes, it sounds like you have an intermittent short circuit in your battery or positive battery cable.

Can you try this test and let me know?

https://www.2carpros.com/articles/car-battery-load-test

Please let us know what happens.

Cheers, Ken
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Saturday, March 31st, 2018 AT 12:00 PM
Tiny
GRMOLL
  • MEMBER
  • 4 POSTS
  • 2004 CHEVROLET IMPALA
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 14,000 MILES
Car starts most of the time cold, then stalls after a few minutes. I have replaced the fuel pump & fuel regulator, bot the problem still is there. It starts to run really bad just before stalling & I noticed that the exhaust is red hot just after the CAT.
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Wednesday, January 20th, 2021 AT 10:37 AM (Merged)
Tiny
LEGITIMATE007
  • MECHANIC
  • 5,121 POSTS
This sounds like a fuel pump or the crankshaft angle sensor has gone out. When you turn the key to the on position without cranking the engine over can you hear the fuel pump run in the tank for 5 seconds?

https://www.2carpros.com/articles/car-cranks-but-wont-start

and

https://www.2carpros.com/articles/engine-stalls

Please run down this guide and report back.
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+1
Wednesday, January 20th, 2021 AT 10:37 AM (Merged)
Tiny
GRMOLL
  • MEMBER
  • 4 POSTS
There is no engine light on, I plugged a scanner into it and it said there were no codes, the live feedback while it was running said everything was ok. I can smell fuel and see black smoke out the tail pipe when I rev it, the fuel pressure is 44- 50 psi. I took off the cat but cannot look into it because of the curves in the pipe, the rear o2 sensor is white, the front o2 sensor in the exhaust manifold is black with suit. The car seems to be running rich and I suspected that was why the pipe on the rear of the cat got red hot, if the cat was plugged would the back pipe get hot? Could I have a bad o2 sensor w out a service light? When I had the cat off I tapped it on the ground and only got a little bit of gray powder.
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Wednesday, January 20th, 2021 AT 10:37 AM (Merged)
Tiny
LEGITIMATE007
  • MECHANIC
  • 5,121 POSTS
Well according to what your saying fuel is dumping into the system and unburned, I suspect a leaking injector or injectors.
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Wednesday, January 20th, 2021 AT 10:37 AM (Merged)
Tiny
GRMOLL
  • MEMBER
  • 4 POSTS
I have checked all the injectors and found a shorted one on #3 I got a new one all fixed:)
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-1
Wednesday, January 20th, 2021 AT 10:37 AM (Merged)
Tiny
LEGITIMATE007
  • MECHANIC
  • 5,121 POSTS
Glad you could get it fixed, that kind of problem can be tough. Please use 2CarPros anytime we are here to help.
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Wednesday, January 20th, 2021 AT 10:37 AM (Merged)
Tiny
NYGIANTS145
  • MEMBER
  • 2 POSTS
  • 2004 CHEVROLET IMPALA
  • 3.8L
  • V6
  • FWD
  • AUTOMATIC
  • 98,000 MILES
Hi I swapped my 3.8l motor for a 3.8l supercharged motor. The car will shut off while driving. The gas gauge doesn't work anymore. It will read full for about 10 sec then read empty. I replaced the sending unit/fuel pump, gas lines, Mass air flow sensor, and throttle position sensor. I get a p0101 code was talks about my MAF. Please help.
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Wednesday, January 20th, 2021 AT 10:38 AM (Merged)
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
If you put a supercharged motor in it you need to update the computer to same. Check the following items in pic but a pro should do some of them. Also check to make sure duct work form maf to throttle body has no holes in it or is installed correctly
Image (Click to make bigger)
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Wednesday, January 20th, 2021 AT 10:38 AM (Merged)
Tiny
NYGIANTS145
  • MEMBER
  • 2 POSTS
I did have my computer reflashed. I will get the stuff in the pic checked. Thanks
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Wednesday, January 20th, 2021 AT 10:38 AM (Merged)
Tiny
EASMOKE75
  • MEMBER
  • 1 POST
  • 2004 CHEVROLET IMPALA
  • 0.8L
  • 6 CYL
  • AUTOMATIC
  • 202,300 MILES
I changed the ignition cylinder lock. Programmed new keys next day had to reprogram keys again. A week later as I was driving all lights on instrument panel started going out then it just shut off. The trunk push button doesn't work anymore and the new keys don't work so I have to use old ones. I bought this car from someone and don't know what else us going on.
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Wednesday, January 20th, 2021 AT 10:39 AM (Merged)
Tiny
MOTOR MASTER
  • MECHANIC
  • 279 POSTS
Hello my name is Dave.

According to the manufacturer's instructions there is no need to do any reprogramming when changing the lock cylinder as all the electronic coded components are located in the cylinder housing.Have you checked for any trouble codes? If you haven't I would recommend checking for them.

Here is a link to our tutorial on how to check for trouble codes:

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

In case there are no codes I am pasting a copy of the relearn procedure for the security system and would try that in case something went wrong when it was last performed.

30 MINUTE LEARN PROCEDURE

TOOLS REQUIRED
None

1. Turn ON the ignition, with the engine OFF.

2. Attempt to start the engine, then release the key to ON (vehicle will not start).

3. Observe the SECURITY telltale, after approximately 10 minutes the telltale will turn OFF.

4. Turn OFF the ignition, and wait 5 seconds.

5. Repeat steps 1 through 4 two more times for a total of 3 cycles/30 minutes (the vehicle is now ready to relearn the Passlock Sensor Data Code and/or passwords on the next ignition switch transition from OFF to CRANK).

IMPORTANT: The vehicle learns the Passlock Sensor Data Code and/or password on the next ignition switch transition from OFF to CRANK. You must turn the ignition OFF before attempting to start the vehicle.

6. Start the engine (the vehicle has now learned the Passlock Sensor Data Code and/or password).

7. With a scan tool, clear any DTCs if needed (history DTCs will self clear after 100 ignition cycles).
Please keep us up to date on your progress and thank you for using 2CarPros!
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Wednesday, January 20th, 2021 AT 10:39 AM (Merged)
Tiny
MELI123
  • MEMBER
  • 5 POSTS
  • 2003 CHEVROLET IMPALA
  • 170 MILES
My car shut off for no reason ive had 4 mechanics look at it and no luck they told me it was the fuel pump then the mass air flow sensor then a throttle body position sensor then the spark plugs. Ive even took it to the chevy dealer and they told me vaccum leaks please help me.
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Wednesday, January 20th, 2021 AT 10:40 AM (Merged)
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Give me a list of what was done.

Give me any codes as well

Roy
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Wednesday, January 20th, 2021 AT 10:40 AM (Merged)
Tiny
MELI123
  • MEMBER
  • 5 POSTS
What was done new fuel pump new mass air flow sensor new throttle body position sensor new spark plugs and there are no codes when they diagnose it
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Wednesday, January 20th, 2021 AT 10:40 AM (Merged)
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
When does it cut off?

Roy
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Wednesday, January 20th, 2021 AT 10:40 AM (Merged)
Tiny
MELI123
  • MEMBER
  • 5 POSTS
Whenever I can be going 60 and it shuts off or I can be going 20 and it shuts off
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Wednesday, January 20th, 2021 AT 10:40 AM (Merged)
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Does it start right back up?

Roy
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Wednesday, January 20th, 2021 AT 10:40 AM (Merged)
Tiny
MELI123
  • MEMBER
  • 5 POSTS
No the only way I can get it to start back up is either wait 4 hours or spray some starter fluid in the filter like toward the throttle body. And I dont want to keep doing that because im pretty sure it will mess up the car even more
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Wednesday, January 20th, 2021 AT 10:40 AM (Merged)
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Then it is fuel delivery issue.

If the fuel pressure is correct, something in the injector area may be the culprit

Roy
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Wednesday, January 20th, 2021 AT 10:40 AM (Merged)

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