I have been tormented by this car, a 2005 Chevrolet Malibu Maxx with 200,000 miles and it’s P0171 and P0174 problems for over 6 months. In this time it has been in the shop multiple times and it still throws the errors. I have seen code P0507 once… But only once… These are the only codes it throws.
Please note that other than a slightly rough idle at 7-800 rpm and and an annoying jingle from the muffler at 1500 rpm the car runs perfectly.
At least it does until it throws the “Too lean” error codes and dies at the side of the road. Then once the codes are cleared it works perfectly until the next time. Which can be as little as 2 miles in stop and go traffic or 2 hours on the freeway.
This all started when idiot me put bad gas in the car. I eventually worked it through, changed out the plugs and wire set and ran a few cans of Sea Foam and fuel dryer through the car in several tanks of gas. However since then I have had this reoccurring problem of the error codes.
Chevrolet’s notorious 3 bings and “ENG PWR REDUCE” and basically your car turns into a paperweight until the codes are cleared.
Since then I have replaced the throttle body, Mass Air Flow sensor, confirmed the air filter is very clean AND purchased my own wireless OBD II diagnostic tool so I don’t get stuck at the side of the road any more… But the problem is still happening.
My mechanic has examined the engine and says there are no vacuum leaks in the engine and it appears to be sound. He says that he cannot find anything obviously wrong with it to fix and to drive it until it throws an error we CAN fix…
Thus I am driving it around running scans using the OBD II scan tool… Which, thank the lord, is reporting something! WHAT DO THEY MEAN!!! HELP!!
I have a guess that they might indicate a stuck open EGR valve? Maby? But what do I know… I studied computers not cars…
thanks for any help or suggestions!!
Sean in Cincinnati
All test not listed passed or were incomplete.
I have checked all fuses and none are blown.
Rich to Lean sensor threshold voltage(constant) - Catalyst Monitor Bank 1
Max: 41,243mHz Min: 20,512mHz
Test result value: 288mHz
Low sensor Voltage for switch time calculation - Catalyst Monitor Bank 1
Max: 41,245mHz Min: 4,128mHz
Test result value: 800mHz
- EGR Monitor Bank 1
Max: 40,973 Min: 26,816
Test result value: 14,080
- O2 Heater Monitor Bank 1 - Sensor 1
Max: 41,113 Min: 20,528
Test result value: 6,976