Check engine light when towing and speed > 60mph
The check engine indicator on my 2003 Suburban comes on periodically for a few
seconds. This happens when I am towing a camper. I have to first exceed 60mph,
then slow down. When the engine is not under as much load, the check engine light
blinks on and off until it is under load again. In other words, if I am accelerating or
maintaining my speed, nothing happens. If I am coasting, the check engine indicator
blinks on and off.
This does not happen when I drive at or below 55 mph. It also does not happen when I
am not towing the camper and driving at any speed.
As the light has came on it has stored codes, so swing by a parts store that can read the codes, write them down then repost them back here and someone will jump in and help you with diagnosing the problem.
There were several codes. The one I got this time and before is P0300 - cylinder misfire. I also got P1172 - fuel pump transfer flow insufficient - this time but never in the past when I had the codes checked.
First thing to do is change the fuel filter, it is located in the frame rail on the drivers side, then dump in a can of SeaFoam in the fuel tank. These codes could be related due to a fuel delivery or an injector problem, the Seafoam will clean thing up inside the fuel system, you should also check the spark plugs for any abnormal wear.
The fuel pump was replace in March 2014. The fuel filter was replaced in December 2015. Every long trip I take, I fill up with Premium from BP. Just did that a week ago. I doubt its the spark plugs but I can check that next.
I would still try the SeaFoam.
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