Terrible surging issues

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SnowDrifter

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In a bit of a bind here. I'm off at school, away from all my tools except for this POS tuner that has very basic live data and code read function.

300 mile drive, all was good until 250 miles in. Had an occasional stumble every 5 minutes. Almost felt like thre torque converter locking/unlocking HARD. Checked tranny fluid level and ran through the gears, found no issues. Later on the issue seemed to reveal itself as an engine issue and not a trans issue

So I continue on my drive, it happens more and more often. In playing around, I put my foot to the floor, tranny selected the right gear, then I got no power and some RPM fluctuations.

I set some live data in my tuner to view MAP, MAF, TPS%, and total misfire count. Right when it cuts out, I get 1 or 2 misfires, then nothing. It idles OK, I didn't see anything odd in the live data. It just acts like a ***** when I try to give it gas, even in gentle driving. The issue got worse and worse as I drove.

As a quick update test, I unplugged the maf. No change.

Vehicle is a 2005 tahoe 5.3 gas, 116k. all maintenance up to date. Air filter/plugs/wires/trans fluid/filter/intake gaskets/knock sensors were done 4000 miles ago.

At the onset of trying issue, I noticed some spark retard but now that it's really bad, not any more. My little too doesn't have a graph function or appropriate refresh rate to see what the O2 sensors do when the stumale occurs. Fuel trims at idle look ok, however they jump to between 30 and 50 under load

If I turn off the ignition for 5 mins. The problem gets better for or a short period of time before it comes back.

Now since I'm away from all my diag equipment and tools it's a little difficult for me to do anything with this. I'm leaning towards fuel pump. Any ideas on things I can check? I'm a bit limited here as I'm away from all my diagnostic tools. Or barring all else, are there any reputable shops/people in Pullman WA?

See here for a snippet off the issue. It seems to be load dependent, not speed dependent. Doesn't matter what gear the transmission is in. Doesn't matter if I'm going 75(which I can only get to going down hill now) or 10mph. If I hit the gas, it does this. If I press the gas more, it goes from surging to just about nothing. The transmission will select the proper gear, then the engine doesn't chooch.
 

rockola1971

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Throwing any codes? Possibly TPS Sensor. Id get a good fuel pressure check. Drop by an auto parts store like Autozone, etc. They will have a gauge to check it for free. As Redrocket....have them scan the inlet and outlet of the cats. If bad the outlets will be substantially lower in temp than the inlets typically. Id expect some codes from the downstream 02s also.
 
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SnowDrifter

SnowDrifter

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I was playing around with the thing some more. I hate to say it since I'm incredibly **** retentive when it comes to doing all my own work.. But the next place it's going is the shop. The thing barely drives, is getting worse, and I want to avoid the tow bill if I can
 
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SnowDrifter

SnowDrifter

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Looks like it's fuel pressure related. Now the real question is... How do I differentiate between a failing pump and a failing pump control module? The vehicle drives normally on cold start. After driving for 20-35 mins the issue presents itself and gets worse with time

 

rockola1971

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Usually your Fuel Pump Control Module is either on or off and no in between which causes the same for your fuel pump. There is an elctrical fault that could cause intermittent on and off but you would be able to hear the pump coming on and off. That whine of the pump would be obvious if it were cycling on/off rapidly. I would check your fuel pressure regulator. See if the vacuum line is on it. Check the line for breaks, holes, cracks, etc. Whats the history on your fuel filter? Been changed lately? If i had to bet, I would replace the fuel pressure regulator.
Check this vid out for location of regulator and how to change. Its for a suburban 5.3l but yours should be the same location and probably same part number too.
 

rockola1971

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Fuel filter, stuck open injector which i doubt since you havent complained of gas smell or bad fuel pump. Your pressure as im sure you know is way too low. Its tattling on itself.
 
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SnowDrifter

SnowDrifter

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Fuel filter, stuck open injector which i doubt since you havent complained of gas smell or bad fuel pump. Your pressure as im sure you know is way too low. Its tattling on itself.
No way around it. Gotta drop the tank I suppose.

Fuel filter for my year got moved to inside the tank with the pump
 

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