Thnx for all previous input, Had the codes pulled by local shop, p0135,p0401,p0441, so this gives me somewhere to start. Has anyone expierenced problems with the feeder tube to egr valve rusting or plugging up? Guy at shop said its a common problem with gm. This thing bucks a little from 50-55mph but that its, below 50 its fine and above 55 its fine. Where is the egr valve located? Thnx

 

What does each code indicate as related systems?

 

P0135 - HO2S Heater Circuit Bank 1 Sensor 1
I would start by swapping the upstream O2 sensors side to side & see if the code changes to P0155. If it does, change the O2 sensor.

P0401 - Exhaust Gas Recirculation Flow Insufficient Detected
Remove the EGR valve (center of the engine directly above the water pump) and clean it. The Tech Article on EGR cleaning will run you through the steps.

P0441 - Evaporative Emission Control System Incorrect Purge Flow
You could try cleaning the EVAP purge solenoid located on the engine near the ignition coil.

The bucking at 50-55mph could possibly be something completely unrelated, but get at least the first 2 codes dealt with and see how the truck runs.

 

Does it idle rough at stops?
I had a bad fuel rgulator,and was rough idle and eating gas bad..

 

Im only finding 2 02 sensors one before the cat and one after. Ive been told some have 4, some have 2 and some only have 1, the tech wrote down p0135 02 heater circuit bank 1 sensor 1, if that helps any. Also my 02"s are a 4 pin plug, Counter guy ar Oreilly told me all he had were 3 pin.

 

A 95 will only have 2 exactly as you have found. The 96-97's had 4 while the 98+ have 3.

Do yourself a favor and buy AC Delco O2 sensors.

 

Thnx again, since I only have 2 02 sensors should i still try and swap them to see if code changes? Does one go bad more often than the other? I can get the a/c delco AFS75 02's online for 39.99 but didnt wanna buy 2 if not needing both...

 

The O2 sensor closest to the engine (between the engine & the catalytic converter - called the upstream sensor) is the only one that has anything to do with fuel management in the engine so that is the only one I would recommend changing. Only change the downstream sensor if you get a code for it.

 

Replaced the 02 sensor using the recommended a/c delco unit and mileage went from around 9 mpg to 14 mpg, next will be the egr cleaning. Thanks for the help.

 

Just curious. Did the SES light was on? I have a similar problem, I'm getting 8-9 mpg on the last 2 fill ups but no SES light on or rough idle or problems starting. Anyway, my question is, can there be codes on the system without the check engine light on?