so, P0174 and P0171. Runs like crap when hot. Thats the only code, but they will be a bitch to get out, lol. Any other options that could throw that code and NOT be the o2 sensors?
It is unlikely both o2 sensors went bad at the same time. I'd try cleaning the maf sensor first. I would also check the fuel pressure on the rail to make sure it is in spec. Given the age of the car it wouldn't be a bad idea to check and replace all the vacuum hoses as well.
On a vehicle that age, whether there are codes or not, change the O2 sensors! They will be dirty, even if they are not defective, and that makes a HUGE difference to fuel consumption. In fact, dirty O2 sensors the most common cause of catalytic converter failure, as they cause the car to run rich which fouls the converters.
Its had the lean bank 1 / bank 2 for some time. I cleaned that big ass MAF already, replaced the CPS, found the vac leaks (i think) and now down to just the lean codes. Is it work swapping the back with the front to see if the codes follow to the rear? I like to be sure before I just start buying replacement parts, but wth..
I can't say for sure whether the front and rear o2 sensors are interchangeable or not. Did you check the fuel pressure on the rail? Might not be a bad idea to look at the voltage sweep on the throttle position sensor as well, but you would probably see a TPS specific code if it were involved.
well, kinda blowing me away on the fuel pressure and voltage sweep. The last time i used my multimeter was in the Navy on a Unisys mainframe. I have 5 kids and 60 hr week job so not a lot of time to search and review all the threads out there. Can you dumb it down for me?
According to Napa your Roady has 4 O2's and they are all the same part number, bank one is before the cat bank 2 is after, the front O2's go out about three to one over the rear. Cleaning out the air flow meter isn't a bad idea but in my experience a lean bank usually refers to the O2 or a vacuum issue such as a line or say a throttle body or intake gasket. Being it's older and depending on mileage it may be advantagous to have it diagnosed then do the repair yourself, you could throw a lot of expensive parts at it and still not fix the problem.
On the fuel rail you should see a Schrader valve, usually at the back of the engine where the fuel supply line comes in. You need a fuel pressure gauge with the correct adapter to read the pressure. There are published specs for each vehicle and the car will only run properly within a narrow range. If the pressure is low, then you have to splice your gauge into the fuel line before the fuel filter. If it's OK, then replace your filter. If it's still low, then your pump is weak. As for sweep, all vehicle sensors work from 0 to 5 volts. If you hook your multimeter up to the TPS and operate it thru-out its range, it will be near zero at rest and advance to 5 volts as it nears wide open. With all sensors, you have to know which wires to hook your meter to or you can damage the sensor.
New O2's and Same ol crap So new O2's in the front of the cats. Ran great for an hour, shut her off and then 15 minutes later no start. What the hell else could it be from the codes I got. What would jack the fuel/air after its hot? Thermostat? Vac switch? Have not pulled the codes yet since the new O2s...dammit
If you think education is expensive, consider the price of ignorance. If you start throwing parts at it because of the idle speculations of people with unknown backgrounds, it will cost you those parts plus what you have to pay when you have to actually take it to someone who can fix it. Not all problems will set trouble codes. Likewise, some codes will be set as a result of other problems. All must be dealt with to solve the problem. Check for spark. If you have spark, try to fire the engine on ether. If it fires, check the fuel pressure. It will take a gauge and whatever special adapter is required to hook it up to your system. If you don't have the necessary equipment, take it to someone who does and quit wasting your money. I am assuming you have a 5.7L with MFI. The pressure with ignition on should be 40-47 psi. With the fuel pressure return line restricted briefly, it should be 47 psi minimum. If you can get it running again, it should read 30.5-44 psi at idle.
I agree. There are tons of things that can cause these codes. Weak spark (I suspect ignition trouble since it "runs like crap when hot") will cause lean O2 sensor codes as well, because they are OXYGEN sensors, not fuel in the exhaust sensors. If you don't burn the air in the cylinder, the O2 sensor will read it and claim it is too lean, and respond by adding more fuel. This makes it even more likely that the engine will further misfire, dumping more unburned oxygen into the exhaust. It becomes a vicious cycle where the computer makes things progressively worse while trying to make things better. It would help to have some emissions data from the tailpipe to see what exactly is going on. Hight CO and HC with low O2 would indicate a bad O2 sensor. High HC and low CO, CO2, and high O2 indicate an ignition fault. Diagnosing these faults requires expertice. It is better to pay to have a qualified tech spend an hour or two diagnosing it than to throw part after part at the car and fix nothing. The key is a "qualified" tech, not a backyard mechanic or the guy down the street "that fixes cars". Fortunately you have a relatively easy car to fix by today's standards. However, it is not a car you can just guess away at. I am a drivability specialist and I would not be willing to offer a diagnosis without physically examining the car myself. The speculations I gave you above were just to prove a point. You need someone who can read and interpret the data to zero in on the problem, not just guess at it until the problem goes away $5,000 later.
