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99 suburban 454 bogging under acceleration

raposak

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raposak Enthusiast

raposak

Posted
Posted

99 Suburban 2500 with a 454 bogs down bad while under load while giving it some throttle. It has a strong air sucking sound while it does this. I hooked up a fuel pressure gauge and here are the readings.

 

Truck cold: ignition on truck not running 50psi and drops down to 22 in 5 minutes

Truck cold: Running at 47psi

Truck cold: 2000 rpms at 47psi

Truck hot: 47psi

 

No matter what rpm when hot or cold, it stays at 47psi. So i'm thinking its either the fuel pump or the pressure regulator. What do you guys think?

shortyb Enthusiast

shortyb

Posted
Posted

I am no mechanic nor have I ever had a 454 but I used to have a 98 Sierra with a 350. It done the same thing you explained. Mostly if I was on the highway and went to climb a hill. (under a load) it would bog down and sputter..

I hooked it up to a diagnostic computer and It had two mis-fires (spark plugs). I didnt even think about that because they were fairly new plugs. They didnt have 10k on them. After that, I started using top of the line plugs.

Hope this helps.

txab Senior Enthusiast

txab

Posted
Posted

Should be 55-62 and should hold at 48 to 52

 

 

Have you checked for codes?

raposak Enthusiast

raposak

Posted
  • Author
Posted

New twist to the problem. I just discovered a puddle of rusty water
under the truck coming from the water pump. I looked in the radiator to
discover that it is quite low on fluid. So the next question is would
low coolant cause the bogging? I was doing some reading on the coolant
sensor and the entire engine performance is based on what that little
sensor tells it.

raposak Enthusiast

raposak

Posted
  • Author
Posted

Well I swapped out my regulator and its still doing the same thing. A mechanic friend of mine suggested that my cats could be clogged.

txab Senior Enthusiast

txab

Posted
Posted

Then have your cats checked and then go back to the fuel issue. Your listed pressures are below spec. Even a few lbs off can cause performance issues

 

 

 

If the fuel pressure is less than 344 kPa (50 psi) at idle, it falls into the following 3 areas:

• The pressure is regulated but less than 344 kPa (50 psi). The amount of fuel reaching the injector is sufficient, but the pressure is too low. The system will run lean, hard starting cold, no start, overall poor performance, and may set a DTC.

• A restricted flow causing pressure drop -- Normally, a vehicle with a fuel pressure of less than 300 kPa (44 psi) at idle is inoperable. However, if the pressure drop occurs only while driving, the engine will normally surge then stop running as the pressure begins to drop rapidly. This is most likely caused by a restricted fuel line or plugged filter.

• A leaking or contaminated pressure regulator valve or seat interface may not allow the regulated pressure to be achieved

raposak Enthusiast

raposak

Posted
  • Author
Posted

Thanks for the information. Is there any way to be sure that its the fuel pump before swapping out? Its an expensive part and a pain to drop a 43 gal tank. I'd like to make sure before spending the money and time.

grampadirt Senior Enthusiast

grampadirt

Posted
Posted

I think I'd change the pump just for piece of mind.They all go out eventually.How many miles on the Burb?Changing the pump is a PITA but doable in your driveway....get a friend to help.I've changed the pump in my '95 twice.Be sure to get a Delphi pump.

 

If you live in SoCal I'd be glad to help :thumbs:

raposak Enthusiast

raposak

Posted
  • Author
Posted

well that was a waste of time and money. replaced the pump and its doing the same thing. Tomorrow I'll gut the cats. and don't worry, I'll replace the cats if that is the problem. Oh and the truck only has 76K miles.

raposak Enthusiast

raposak

Posted
  • Author
Posted

Well that was it. The front Cat was clogged something fierce. Now that I know the cats were the problem, i'll be ordering a new exhaust.

  • 1 month later...
MeenGreenAudio Enthusiast

MeenGreenAudio

Posted
Posted

we are having problems similar to this on the 98 sierra with the 350 and it was diagnosed as a hole in the sealed fuel system somewhere, imagina a hole in your straw and no fluid is coming through. well the fluid is gas and your engine is not getting enough. has it ever felt like it is missfiring while driving at a constant speed? and If so they no longer make "the straw" so im looking for one because i need the truck working. Does anybody know where you can find parts that they no longer make?

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