Truck Repair: Loss of horse power intermittently, chevrolet silverado, rush hour traffic

Question
Van,

Thanks for quick response.  I finally had the vehicle towed to a Chevrolet Dealer.  The truck did not stall out on me,it was acting funny again and I didn't want to take the chance of breaking down in a bad spot during rush hour traffic.  Plus all of this has taken it's toll on my nerves!  I call the dealer this morning and explained everything to him that I wrote in my initial email to you.  He said, "your fuel pump may be going bad.'  This is what I am afraid of.  Having a dealer telling me it is the fuel pump.  I have spoke with a few people who state that a fuel pump does 'start to go bad' and work intermittently.  It is either good or bad.  Can you confirm this for me?  Also, someone told me to put 'dry gas' in my tank.  What is your take on that.  Sorry for being such a pain in your 'gas'  hee hee.  A little humor......  :)

J

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Followup To
Question -
Hi, Van.  I have a 2002 Chevrolet Silverado 1500.  4.8, 8 cylinders.  I have not been very good at maintenance until recently.  The truck has 96,100 miles on it.  Since a week ago this past Saturday (4/15) I have intermittenly lost horsepower. It feels like I am about to run out of gas....bucks a little and lose horse power.  It has never really stalled with the exception of yesterday. It started up again with no problems after 4-5 starts.  I have replaced: the fuel filter, all spark plugs and wires, oil change with lucas and a fuel induction service.  I was down to less than 1/4 of a tank when it actually stalled on me yesterday.  I took it to a BP and filled it up with Amoco 97 Octane.  Two things that make me wonder:  I filled up with gas on the afternoon of April 14th.  The "Service Engine Soon" light came on by early evening.  Saturday morning, after driving on the highway for about 20 minutes, I experienced the first problem with loss of horse power.  It has happened several times since then.  In the beginning, it was only happening after I have been driving for a little while.  However, lately, it starts up within 5 minutes of driving and sometimes as I start to drive.  I filled up yesterday with the 97 octane, drove home and about 3-4 times over the next 4 hours, would start it up and rev the engine.  The "Service Engine Soon" light actually went off!  It stayed off until this morning when it came back on.  It bucked very little on the way to work (about 10 minutes into the drive) but not nearly as bad as it had been the last 4 days.  Bad gas, maybe?  Oxygen sensor?  I am told that it is not my fuel pump.  I hope that it isn't!!  If it is bad gas will the problem fix itself since I have put amoco 97 in it?  Thanks for any help or advise you can offer.

Judy


Answer -
Hello Judy,
Read the codes if possible.
I would expect it to give a EGR code. Sounds like the egr valve might be seating on some carbon. That would act like a big vacuum leak, especially at idle, but could feel like a surge while cruising.

It can be removed and cleaned.


Van

Answer
Hello Judy,
The fuel pump itself usually either pumps, or it doesn't pump.
There are, however, several things that might keep the fuel from getting injected into the engine properly.
A dirty filter is one of them, but usually a dirty filter stays dirty, and won't get better.
A split hose inside the tank can loose pressure, but that, also, won't be intermittent.
A faulty pressure regulator, which could be intermittent if there is a problem with its control system.
A poor ground or wire connection to the pump, but other than a dirty or loose ground, that will generally just quit.

All of those can be verified, or eliminated with a fuel pressure tester connected "when the problem is happening".
If the pressure drops, thus causing the problem, then you look at the operating system or the pump.
But if the pressure is up to specs when the engine looses power, that eliminates the pump as the problem.
I would never replace a pump without verifying it as the problem with a pressure test.

Your power loss, if the fuel pressure stays up, can very easily be the EGR valve.

I hate to see someone pay for that pump job, only to need further work afterwards, and the shop say "well....you were going to need a pump soon anyway".

I have seen pumps wear out in under 50,000 miles, but I have seen trucks with over 200,000 and still on the orriginal.

Dry Gas....if you have some good reason to think you have water in the gas, like catching some during a filter change or pressure test and seeing the water, then run some. Otherwise, it won't do anything for you.
But if you think you got some dirty or bad gas, I would for sure have the tank cleaned out.

But reading the stored codes should be the first step.

Van