97 5.7 Burb with intermittent loss of power

[v8_ranch]

I have a 97 K1500 Burb with 5.7 and AT. The truck has about 225,000 on the clock. I just started having a strange problem. I was driving home from Nashville and and after an hour, I started having a total loss of power while going up a hill. If I gave it any gas at all, it was just bog down and RPM's drop to "nothing". Manage to crawl to top of hill and then going downhill, it picked speed back up, but if I gave it too much gas, bogged down again. Pulled off the next exit and as I came to top of ramp, the truck died. Sat for about 5 miinutes and tried to start it again and it cranked and fired right up. While in Park, I revved engine and seemed to rev fine with normal throttle response. Pulled onton interstate and car seem to pull(accelerate) normally again. Managed to get home (another hour) without any issues. The SES light did come on. Before I could get to somewhere to get codes checked, it did it again. Almost same exact symptoms(truck had been driving completely normal up to this point): drove about an hour, then bogged down going up a hill or under any acceleration at all. Pulled off into gas station and died. Gas gage was at 1/4 tank, so I thought maybe my gage is off and it is lower on fuel than indicated. Put some fuel in and started up (again about 5 minutes of rest), and truck started right up and drove home with no issues.

So I got the codes read and it had both O2 sensors flagged, both banks running lean, and a MAF fault. Took it into mechanic and had him check it out (this shop just last year replaced the: fuel pump (with a delphi), fuel pressure regulator, both o2 sensors - I myself, have just replaced the cap, rotor, plugs, wires, and fuel filter within the last year). Again, the truck starts right up on first crank iwth no stumbling like it did before with bad fuel pump. The only issue is this loss of power while driving. The mechanic said my pressure was running 55 and while low, was not convinced it was a bad fuel pump yet. The MAF was interesting to him, but it did not SET any info with the code when it came in, so he reset everythign and asked me to bring it back in if the SES came in again. So i took it on a drive yesterday, and it was running a little rough. I had a friend let me swap in his MAF just to check it (his was relatively new), and no change in the slight stumble on acceleration. When I say it stumbles, it is more like a slight stumble, it would still accelerate .

But then I decided to try revving hard from different speeds (stopped to 55mph). No matter what speed, if I floored it, it would rev the engine up to about 3500 and then stall there (transmission not shifting into next gear) until I let off the accelerator slightly. This repeated several times, and then the SES came back in. I have not checked the codes yet. I did pull over an change the fuel filter (had a new one waiting). No change after the new fuel filter - does the same type of stall when flooring. Then I noticed it was doing the total loss of power again (like the first time it happened), and same exact results - oulled over, stopped engine, restart after 5 minutes, and drove home with no issues other than the slight hesitation I spoke of earlier.

I know this is a book and I apologize, but trying to give you as much info as I have about this intermittent problem I am having. Could it possibly be my stupid fuel pump has crapped out again? If so, I do not know if I would recommend Delphi over any other brand then. It has only been a year.

Help

[777stickman]

1st off we need the code numbers not a basic description of the codes.

Fuel pressure at 55 psi is at the low end of pump off (55-60). Pump running is 60-66.

Other things to check are the TPS and ECT. Both need a high end scan tool to check.

One other thing to check is the PCV valve.

[v8_ranch]

P0131
P0151
P0171
P0174

I cannot remember the code for the MAF

[v8_ranch]

took truck into shop again this morning. Fuel pressure was only 48 this morning. Pump, strainer and sending unit are getting replaced as we speak. hopefully this is only problem. Pump (Delphi brand from O'Reilly's) conveniently died just 3 months after warranty expired... of course! So much for the Delphi pumps

[777stickman]

Yeh all those codes are pointing to a lean condition on both banks.

Don't give up on the Delphi pumps. I buy mine from gmpartsdirect.com or local AC-Delco stores. I always supply the VIN as these pump can be very VIN specific.

Other areas for your shop to check are the ground connection and the wiring plug itself for burnt or melted connectors. One or both of these can cause the pump to not get the proper voltage path for the pump to run at full blast.

Let us know how it turns out for you.

[v8_ranch]

The sending unit was also replaced as they said it was showing signsof wear on the wiring/plugs. Truck runs better but still has a slight hesitation. They are saying it is a separate issue and that it is being cuased by a leaking intake gasket. The complete loss of power was being caused by the pump conking out over time (I guess this explains why it seemed to happen after about an hour of driving), but the continuing minor hesitation is due to the intake leak. They want $620 to do the work. Is this worth paying the money or is it not a bad job if you have the shop and tools?

One thing I was wondering about: the parts place mentioned to me that I should keep greater than a 1/4 tank of gas as much as possible, as the low tank level can cause the pump to overheat. I have never had this issue before with any vehicle. Are they blowing smoke or is there something to this?

[777stickman]

Keeping the tank above 1/4 is recommended by many on this forum.

As far as the DIY intake gaskets are concerned there is a thread at the top of this Sub forum that you can look at. Biggest issue is getting the dist back in its proper position and then having it checked and adjusted to 0 +/- 2 degs (cam offset/cam retard) with an engine capable scan tool.

DIY intake ?'s are also at the top of the Silverado and Tahoe forums.