Rough Acceleration W/ Ses Light

Sierra54 · May 15, 2011

I have a 1999 Sierra with about 230,000mi. This morning I noticed that the truck would accelerate then lose power then accelerate and so on... it felt like the gas pedal was being pumped while accelerating. Eventually the SES light came on. Not sure if it could be a clogged fuel filter, dying fuel pump or throttle positioning sensor going bad. The SES light did not come on until after all of the local parts stores closed for the day. I plan to check the code in the morning but would like to have an idea of what I could be expecting. Would a fuel pump or filter that could cause this actually throw a SES code? Also, can parts stores test the TPS?

Thank you,

GMstrong · May 15, 2011

Check your or replace your oxygen sensors.No your fuel pump or fuel filter will not throw a code could also be your egr valve.If its your TPS it will have a rough idle

Sierra54 · May 15, 2011

Truck died on way to parts store. Pulled it home then went to rent scan tool. Was given following codes:

P0171 system too lean bank 1

P0174 system too lean bank 2

P0151 O2 sensor low voltage bank 2 sensor 1.

Not really too sure where to start. Should I just replace the o2 sensor? Not sure which sensor this is. Or could the bad fuel pump or clogged fuel filter cause it to run lean and kill an O2 sensor?

Any help would be greatly appreciate. Parts store open till 8 and I really need to have this fixed today.

Thanks

[email protected] · May 15, 2011

Definitely sounds like the fuel pump went out. Both banks were lean indicated a fuel problem or a dirty maf, and since your truck just quit, the fuel pump is top suspect. It's a good idea to replace the filter also.

Sierra54 · May 15, 2011

I just finished replacing the fuel filter. Cleaned one end and tried to blow through it, hard to blow through and rusty gas came out. Started up after a few tries now runs smooth. Before I changed it the fuel pressure was 20 then dropped to 10 with key in on position, now with it running it stays at 45.

I think 45 is kind of low but I think that this is what it was at every time I've checked it in the past. The fuel pump is original and this truck has over 230,000mi. I usually change the fuel filter 1x every year. I'm going to drive it to return the scan tool to see if it continues to run okay.

Also, could I have ruined the O2 sensor or did it just shaow that code while it was lean?

Thanks for the help!

Sierra54 · May 15, 2011

Running rough on way to parts store. I turned around came home before it died. It's still running rough with fuel pressure between 10-20psi again. Planning on replacing pump tonight.

8.1HD/ALLISON · May 15, 2011

Yeah sounds like the pump is done. I wouldn't change the o2 sensor untill you get the running problem taken care of. It is probably a byproduct of the running lean issue.

jro909 · May 15, 2011

230k on factory fuel pump is crazy...has that thing had any other issues in its life?

Sierra54 · May 16, 2011

Thank God for helpful neighbors!

Replaced the fuel pump with his help. Dropped the tank to do it. No issues with the test drive.

From memory i have replaced: front pinion seal, u-joints, driver's side window regulator, passenger side window regulator twice, intake manifold gasket, fuel pressure regulator, 4x4 switch in dash, speakers rotted in doors. I tried to replace the parking brake shoe but was unsuccessful. The cable seemed to be siezed up. I tried to stay on top of its up keep. Always changed fuel filter every year, oil chaged when idiot light came on switched to synthetic at 85k, trans fluid and filter change every 75k, plugs & wires at 100k & 200K, coolant flush and fill and relaced hoses and belt, mobile 1 in front & rear diff at 100k a few sets of brakes and tires.

Today was the first day I have ever been stranded. I really can't complain when I look back.