Check Engine Light Blinks then shuts off

Joined
Aug 11, 2022
Messages
4
My car: 2008 Pontiac Grand Prix
Engine: 3800 Series III V6
Milage: 92,600
Problem:
Ok weird stuff is happening. When I drive around 62 - 65 mph on the interstate, my check engine light comes on and if I'm on cruise control disables it. It then randomly shuts off with no code. I already replaces all the coils spark plugs and wires and the gas cap, what else could it be?
 

wtd

Joined
Jun 25, 2002
Messages
3,339
Location
southwest Mo.
How many times does it blink? Usually a blinking CEL means it's misfiring. You have replaced most of the things that would cause a misfire except injectors but I wouldn't install a set of injectors without diagnosing it first.
 
Joined
Nov 20, 2006
Messages
29,188
Location
MA, Mittelfranken.de
My car: 2008 Pontiac Grand Prix
Engine: 3800 Series III V6
Milage: 92,600
Problem:
Ok weird stuff is happening. When I drive around 62 - 65 mph on the interstate, my check engine light comes on and if I'm on cruise control disables it. It then randomly shuts off with no code. I already replaces all the coils spark plugs and wires and the gas cap, what else could it be?
Check the cat. Injector issues are usually accompanied by drivability issues, injector codes and high +- fuel trims.
 

GON

$100 Site Donor 2023
Joined
Nov 28, 2014
Messages
3,789
Location
Steilacoom, WA
I would pull the coils and check underneath for corrosion. Will take just a few minutes, very easy to do. Next I would check the plugs, and plug wires.

On a Series III V6 3800 under load getting a temporary flashing check engine light, my experience has always shown a coil, spark plug, or plug wire issue.
 
Joined
Aug 8, 2008
Messages
7,363
Location
Cali
CEL on my 83 Silverado will come on during long idling but goes out once you take off and get the RPM's up.
been this way for the last 25 yrs. :unsure:
 
Joined
May 7, 2004
Messages
13,136
Location
Nokesville, VA
CEL on my 83 Silverado will come on during long idling but goes out once you take off and get the RPM's up.
been this way for the last 25 yrs. :unsure:

Oxygen sensor cooling down and not sending a signal anymore? If it's a heated oxygen sensor, maybe the heater has failed.
 

'08 Pontiac Grand Prix V6

Thread starter
Joined
Aug 11, 2022
Messages
4
How many times does it blink? Usually a blinking CEL means it's misfiring. You have replaced most of the things that would cause a misfire except injectors but I wouldn't install a set of injectors without diagnosing it first.
It blinks until I go down to 55 mph, and then if I don't shut the car off it goes off at random times after that. But it doesn't start till 65, stops at 55 sometimes, other times it randomly shuts off, and then keep driving and it does it again for a bit.
 

'08 Pontiac Grand Prix V6

Thread starter
Joined
Aug 11, 2022
Messages
4
I would pull the coils and check underneath for corrosion. Will take just a few minutes, very easy to do. Next I would check the plugs, and plug wires.

On a Series III V6 3800 under load getting a temporary flashing check engine light, my experience has always shown a coil, spark plug, or plug wire issue.
I replaced the wires spark plugs and coils and nothing helped, all of them are new, and there is no corrosion under the coils
 
Joined
Nov 20, 2006
Messages
29,188
Location
MA, Mittelfranken.de
All the indicators of a partially clogged cat. If the engine was getting misfire codes and so on due to a bad cat pulling the front O2 sensor and starting the engine will usually relieve enough back pressure to diagnose it. In this case I suspect it is not letting enough exhaust out when the RPM's increase for a sustained time.
You can get an exhaust back pressure gauge to test the amount of pressure in the exhaust or a simple vacuum gauge and IR thermometer can also help diagnose it.
This is not the only thing that can cause the issue but I have seen this many times.
 
  • Like
Reactions: GON
Top