i pulled some codes, 173,177 and 542, did a search, but still unclear, please help!

[Mike92Silver]

my inspection is up this month and i pulled 173,177 and 542 when i ran the codes. I replaced both o2s 2 years ago with bosch, i think they are fine, because i think the system is rich and its not the o2s failing! not sure what 542 means exactly, i replaced fuel pump last year. My miles per gallon is like 13! So i cant do the o2 test, i dont have a blow torch or voltmeter. Assuming its not the o2's where should i look? im pretty sure the maf is mine, just replaced the ACT, no other codes showing a failure, so i think its something physical like maybe vacuum leak? how to check for a vacumm leak? my idle is fine by the way, but sometimes i do have to floor the car to start it

 

[rangerj]

Mike92Silver,

If you had a vacuum leak you would have codes indicating a lean condition.

The O-2 sensors "switch" continuously from rich to lean as they sample the exaust gasses. The 173 code indicates that the O-2 sensor is not switching as frequently to the lean side as it should (as often as the computer expects it to).

Is this due to a failed O-2 sensor, or is the exaust gas in fact rich?

The 177 code indicates that the front O-2 sensor is sending a signal that the front bank is always rich.

Your low fuel milage also indicates a rich condition. The question is, do you have bad O-2 sensors, poorly connected O-2 sensors, or a rich fuel mixture because of a dirty aircleaner, or leaking fuel injectors, an IAB (IAC) problem, etc.

As the O-2 sensors are relatively new, I would trust that they are producing accurate information, and look for a reason for your rich condition.

If you have access to a known good O-2 sensor you could replace the front O-2 sensor with one known to be working, and see what happens. If the known good O-2 sensor gives you the same codes, then you will need to determine why you are running so rich.

The fuel pump code could be due to a poor connection, or was triggered by the way you ran the test.

A code relative to a specific sensor does not mean that the sensor is bad or faulty. It means that the computer is not getting the signal from the sensor it is programmed to expect, or is not getting any signal from the sensor. There is a distinct difference.
Hope this helps, rangerj

 

[Mike92Silver]

Well how can i know if my fuel injectors are leaking, my air filter i cleaned last year, i dont think thats it. iab seems fine, i dont have any idling problems at all. So assuming its ignition problem, where do i start? plugs are 25k old, just cleaned them and put them back in, plug wells are fine, plug wires are 53k old? cleaned maf, tps is new, so is the ACT sensor. Not sure what else is causing such a drastic loss in gas mileage!

 

[AutoSHO]

Check your fuel pressure. My car was spitting out 173 and 177 and I am running 50 psi at idle and 65 without vacuum (spec is 30 psi idle, 38-42 no vacuum).

 

[Mike92Silver]

why is your pressure so high? Is that from a leaky injector? is that how you can tell? why would it make it run rich though?

 

[sdpatt]

Mike,

Other than the information that rangerj already provided, there are few conditions that could cause the overly rich condition without registering a CHECK ENGINE light. The two main items that I would look at are the MAF sensor filaments for buildup and the engine coolant temperature sensor for proper output.

Clean the MAF filaments with electrical contact cleaner or intake manifold cleaner. To test the ECT sensor, let the engine run with the car stationary. When the radiator cooling fan comes on, check the position of the temperature gauge. It should be around the "RM" range of the guage.

A third possibility is a failing throttle position sensor. This could also be part of the difficult starting condition. Have AutoZone check it for continuous output.

 

[Mike92Silver]

the ect, is fine, did that, the tps is not even a year old and i cleaned the maf, didnt change anything. My plugs i just cleaned not too long ago and they were in fine condition, 25k old, and the wires are 53k old, The wells are dry too, im like SOL, i cant think of anything else, i mean im only getting 13mpg with EASY driving. I have a feeling with my car, its gonna be something i cant figure out, damn car! its never the obvious!

 

[rangerj]

Mike,

How did the plugs look before you cleaned them? Were they black? Pull a plug now and see if it is black from a rich condition.

A fuel pressure test is not a bad idea. Autosho's high pressure could be due to a bad pressure regulator. A fuel pressure test would eliminate fuel pressure as an issue.

If too much fuel is not the problem, then too little air, or poor ignition is the problem. Your plugs and plug wires are relatively new, right?

Is the MAF sensor clean? Is the IAB clean? Is the throttle body clean around the throttle plate? I have seen situations like yours where the throttle position sensor (TPS)tested within the acceptable range, but was at the high end of the range.

The TPS was telling the computer that you had the throttle open farther than you actually did, and the computer responded by having the injectors spray more fuel, creating a rich condition. Test the TPS. If you get a voltage reading greater than 4.5 volts, I would replace it. rangerj

 

[Mike92Silver]

update, well it is extremly cold here, like wind chill near 0, i got a CE light again, ran the codes, and i got a 114, I just replaced the ACT sensor 2 wks ago! It seems it always acts up when the weather is Extremly cold with the windchill and crap, Also, as soon as the Ce light came on, the car was running great, smooth and powerful. I have no clue why a CE light would do that, but last time it came on when the act sensor threw the code, it did the same thing. Any correlation between throttle response and the ACT throwing a Ce light? plugs looked good, at 25k old, wires are 53k old. Tps was replaced from last year

 

[sdpatt]

It was recently posted that the ACT code can show up during the KOEO test from temperatures below 50F degrees, but I don't recall if it mentioned setting a CE light while driving. That could cause a rich condition and is easy to replace.

 

[Mike92Silver]

ok i have question, i did replace the act two weeks ago, and it seems the CE light has come on when it was extremly cold out, Heres the thing. When the CE light goes off, is it from the ondemand codes, or stored codes. The ce light came on, i got 114( it was like 0 degrees out) but i got 173, 177 and 542. So which code is setting the CE light off?

 

[rangerj]

Mike,

The CE (get engine serviced soon) light is most likely being set by the O-2 sensor codes. The purpose of the CE light is to get the owner to have a polluting situation corrected ASAP.

Do a fuel pressure test. If your pressure is high it may be caused by a blockage in the fuel return line. Also consider the purge canister system. Look in a service manual for the testing proceedures for the purge system.

As rich as you are running, is your exaust throwing black smoke? Is the end of your exaust pipes blackened with soot? These would also confirm your rich condition, and affirm that the O-2 sensor(s) are working right. Just a thought. rangerj

 

[PaulRuffo]

Mike,
I would take their advice and get the TPS tested. Dont assume that it functions properly just because it has recently been replaced. There is always the chance you got a defective part.

Paul

 

[aaronsbiza]

I have noticed a lot of black soot in my exhaust tips, you are saying this is a sign of a rich mixture, which is usually caused by a bad O2 sensor?

 

[rangerj]

aaronbiza,

The O-2 sensors do NOT cause a rich or lean mixture. They sample the mixture as the exaust gases flow past them. They report this information to the computer, and the computer adjusts the mixture by adjusting the "spray time" of the fuel injectors. (the opening and closing of the injectors in miliseconds)

If you have a lean condition, say due to a vacuum leak, the sensors will report this to the computer. If the condition goes on for too long the computer will "code".

If you have a rich comdition, as evidenced by you black sooty exaust, the O-2 sensor USUALLY is not the cause. You look for a reason for the O-2 sensor to code. You check for restricted air flow or poor ignition, such as poor sparkplugs or plug wires.

If the O-2 sensor codes "lean", and you know you are running rich (tail pipe), then the sensor is not operating properly and should be replaced.

The idea is to determine why a sensor coded. Did the sensor code because it is reacting to a problem, or is the sensor, or its connection, the problem. Replacing a sensor just because it causes a code may be treating the symptom instead of the problem.

I think this is why we frequently see posts on the forum like, "I replaced every sensor in the car and it still runs like crap". The codes will give you a lead, but you have to follow it and do the diagnostics. rangerj thumbs_u

 

[Mike92Silver]

yeah the tailpipes are always kinda black, but i thought everyones were since when u got full throttle it runs a bit rich anyway and u get the black soot? the light didnt come on today, not sure what the deal is, the air cleaner i cleaned last spring,(i just cleaned the maf, there was no crap on it from the reoiling, but cleaned it anyway). I hope to check the pressure this weekend and see whats up, im hoping its a cheap replacement or solution!

 

[AutoSHO]

The problem you are having sounds exactly like mine. I would guess your fuel pressure is going to be higher than specified.

Just for reference:
Idle 28-32 Psi (30 nominal)
Vacuum Disconnected from the FPR and plugged at the manifold 38-42 psi (39 psi nominal)

Good Luck!

 

[rangerj]

Mike92silver,

Yes, at wide open throttle(WOT) you should be on the rich mixture side. Do you run at WOT all the time?

The tailpipe is normally going to be dark gray to a charchol color. A rich condition will show up as black sooty deposits, and a degree of black smoke with the smell of gasoline if the condition is real rich.

The O-2 sensors in combination with the computer are calibrated to maintain a 14.7 to 1 air/fuel mixture ratio. The sensor signals the condition to the computer, then the computer adjusts the fuel injectors. (very over simplified)

So, you have one or two O-2 sensors telling you that you have a rich condition. This is supported by the evidence that you are getting very poor fuel milage (13MPG), and the blackened tailpipe. You have further reason to believe the sensors because they are relatively new.

Assuming the sensor is not faulty (for now), the next question should be "what is causing the rich condition"? The two general causes are restricted air flow and poor ignition. Add excessive fuel pressure as a mechanical possibility.

With the advent of these computer controlled cars we add the possibility that a sensor is provideing faulty information, and causing fuel to be added to the mixture when it is not needed, eg TPS, MAF, MAP, ACT, ECT.(etc, get it eek! )

Once you have the problem defined make a list of the possible causes, and start eliminating them by diagnostic testing.

I would not assume that any sensor is not faulty. You may put it low on your priority list of things to check, but do not eliminate it from the list! rangerj

 

[Mike92Silver]

both o2s are telling me, im rich, i know im running rich and they are doing the job, however, no other sensors are fouling up, i would think for any sensor to messing up this bad, it would have to light a CE light. im thinkiin fuel or ignition, see i would think maybe wires since they are the oldest ignition item i have, they are 40k old, but i dont get any noticeable shaky idle or something, my cars a real pain like this, nothing ever fails so noticeably where u can say, ok its this!!!!!!! makes me mad at times. im gonna run some injector cleaner thru the system too

 

[Mike92Silver]

see i know my car is not in the best shape, im having a suspension problem, but thats another thread,lol. so i dont run her hard, my work is only 3 miles away! so not alot of WOT runs, besides its no fun when you know the car is messed up engine control wise.