Gas coming out of exhaust


tabby24
03-09-2012, 11:10 PM
So I had a friend looking at my car to see if I needed new cataltic coverters. When he was reving up the engine there was gas coming out of the bank1 exhaust. Can anyone tell me why? I heard possibly the fuel injectors? If so is there a way to test them and how many does my car have? Im planing on getting all spark plugs and coil packs changed asap. 00 licoln ls sports package v6

shorod
03-10-2012, 10:01 AM
What do you mean by "gas coming out of the bank 1 exhaust"? Are you saying you noticed liquid dripping from the tail pipe on the passenger side, or was there something dripping from the exhaust manifold? Are you certain it was raw fuel and not water?

Moisture will condense in the hot exhaust after the car sits for several hours. That moisture will exit the tailpipe when the car is started. Also, when the catalytic converters are working they will convert the unburned fuel and combustibles to water vapor, so it's not necessarily a bad thing to see moisture exiting the exhaust.

Also, the exhaust on the LS has a crossover pipe so even though there is one tail pipe on the driver's side and one on the passenger side, the two runs of exhaust are not completely separate from each other.

Is there a reason you suspect you need new catalytic converters? Is the engine running rough and/or with a loss of power?

-Rod

tabby24
03-11-2012, 08:51 AM
What do you mean by "gas coming out of the bank 1 exhaust"? Are you saying you noticed liquid dripping from the tail pipe on the passenger side, or was there something dripping from the exhaust manifold? Are you certain it was raw fuel and not water?

Moisture will condense in the hot exhaust after the car sits for several hours. That moisture will exit the tailpipe when the car is started. Also, when the catalytic converters are working they will convert the unburned fuel and combustibles to water vapor, so it's not necessarily a bad thing to see moisture exiting the exhaust.

Also, the exhaust on the LS has a crossover pipe so even though there is one tail pipe on the driver's side and one on the passenger side, the two runs of exhaust are not completely separate from each other.

Is there a reason you suspect you need new catalytic converters? Is the engine running rough and/or with a loss of power?

-Rod

Thank you for replying. Yes It was actually gas coming out of the tailpipe. First I noticed that steam would come out of the tailpipe on passenger side but not my driverside. The gas only came out when he was *reving* up the engine Yes my car runs rough right now and I am only getting like 10 miles to the gallon (expensive). When I take off from a complete stop it acts like it doesnt want to go and will start almost stuttering. I also got the my car hooked up to a computer at aamco and these were the codes that I got. P0171system too lean bank 1 P0174system to lean bank 2 P0430bank 2 cat eff below limit P1112iat sensor intermittent P1565 speed control switch intermittent. I appreciate your help tremendously!

shorod
03-12-2012, 06:42 AM
Codes for a lean system on both banks is not consistent with gas coming out of the tail pipe. If it truly is unburned fuel coming out though, that could explain the P0430 code as the converter will overheat and start to melt down internally if it runs too long with that much fuel coming through.

I would suggest you start by determining why you have the P1112 code since an Intake Air Temperature (IAT) sensor that is giving bogus readings could cause problems with the air/fuel ratio. I'd also suggest you check the fuel pressure and pick up a vacuum gauge and see what your vacuum is doing. Since your LS has the V6, and it's very common for the PCV elbow to fail which would help explain the lean codes, I think you have a nasty vacuum leak causing your driveability concerns.

-Rod

joegr
03-12-2012, 08:25 AM
Codes for a lean system on both banks is not consistent with gas coming out of the tail pipe. ...

Actually, it can be. (I'm not positive that's what's going on here, but...)

Lean is indicated when there is too much oxygen in the exhaust. If there is no ignition, then there will be too much oxygen in the exhaust because none of it got burned. There will be unburned fuel too, but the O2 sensor doesn't know about that.

shorod
03-12-2012, 02:05 PM
Hmmm, I'll have to think about this more. Since stoichiometric would be a reading on the O2 of 0.45 V, below that is lean, above that rich, it would seem the sensor could still report accurately if there is a misfire as the ratio of unburned gas and air would remain. I'm not sure in practice it works that way. I've used the O2 sensor readings in the datastream mode before to diagnose an ignition issue versus a fuel issue when a misfire occurs, so I'm not quite buying in to the above yet. Plus there are codes for banks reporting rich, so if the O2 sensor is unable to identify that (which we know isn't the case based on the O2 sensor readings) what would be the purpose of such rich codes. The diagnostics for rich codes don't suggest only and issue with a restricted air intake path.

Ultimately, if Tabby has the opportunity to find out what the short and long term fuel trim numbers look like in conjunction with the O2 sensor readings while driving the car, that may give better indication as to if there's a likely an ignition or fuel issue causing the problem symptoms.

-Rod

joegr
03-12-2012, 02:20 PM
... Plus there are codes for banks reporting rich, so if the O2 sensor is unable to identify that (which we know isn't the case based on the O2 sensor readings) what would be the purpose of such rich codes. T...
-Rod

The O2 sensor detects rich mixture by the fact that there is not enough oxygen in the exhaust gas. Oxygen is the only thing the O2 (oxygen) sensor can detect. It doesn't detect fuel, combustion products, or anything else.

Too much oxygen = too little fuel, too much air, or no combustion at all.

Too little oxygen = too much fuel, or not enough air, but there was combustion.

Don't take my word for it. Look it up.

shorod
03-12-2012, 10:51 PM
I understand the function of the oxygen sensor, and the voltage generated is with respect to external air. After thinking about this a bit longer, I guess the PCM knows how much air is coming in to the engine based on the MAF sensor or the MAP sensor, depending on which sensor is employed. Since it knows how much air is entering the engine, and the injector pulse width, it knows how much air should be in the exhaust stream for a stoichiometric mixture. Based on that ratio, it could calculate if the mixture is lean or rich.

I still struggle to accept that an ignition misfire could cause a lean code. It seems like if that were the case, there would be no reason to define codes P0172 and P0175 which are codes for rich banks. These codes are set based on the Short Term Fuel Trim and Long Term Fuel Trim values. The fuel trim values are how much the PCM alters the pulse width to attempt to bring the air/fuel ratio back to stoichiometric. I would expect that if the PCM dumps more fuel in to a cylinder/bank to attempt to compensate for a lean condition (therefore increasing the fuel trim) and the O2 sensor reading showed an even more lean condition, it would start to realize maybe it's going the wrong way. But then again, if the amount of air entering the engine doesn't change, but it dumps more fuel in, would the O2 sensor pick this up as any different?

You're making my brain hurt and I cannot convince myself either theory is wrong. Do you have any articles you can point me to that suggest an OBD-II system could indicate a lean condition due to an ignition misfire? I have limited first-hand experience to the contrary, but since I'm not a professional technician (and have no formal training) my experience in total is limited.

-Rod

shorod
03-12-2012, 11:05 PM
Since this discussion got me thinking about MAF sensors, Tabby, does your car happen to have an aftermarket performance air filter? If so, or if you think it may have before you purchased it, the oil from the filter may have coated the MAF sensor element causing the engine to think less air is coming in to the engine that it is, so in turn it attempts to pump more fuel in. This too could help explain why both engine banks could be reporting lean codes. If you have the security Torx bit and are comfortable removing the MAF sensor element, you can clean it with MAF Sensor Cleaner.

-Rod

joegr
03-13-2012, 08:48 AM
Okay, I'm not getting through here.

The O2 sensor senses oxygen in the exhaust stream. The PCM uses this to determine if the mixture is rich, lean, or just right. While the PCM uses the info of how much air is going in and how much fuel it thinks it is injecting, in the end the O2 sensor reading is what is used to determine if it is rich or lean.

Lets think about this a bit.

Case 1: The ignition is working, and there is combustion.

A. If you have just the right amount of fuel relative to air, the exhaust air will have some unburned oxygen in it, but not much. In this case, the continuous O2 reading will establish that the mixture is just right.

B. If you have too much fuel, there will not be enough (or maybe none at all) oxygen in the exhaust air. The O2 sensor will indicate low or no oxygen, and this will trip a mixture rich code.

C. If you have not enough fuel, there will be too much oxygen left in the exhaust air because there wasn't enough fuel to consume it all. The O2 sensor will indicate too much oxygen and trip a lean code.


Case 2: There is an ignition fault and so no spark, so no combustion.

A. If you have just the right amount of fuel relative to air, the exhaust air will still have way too much oxygen in it because there was no combustion, so no oxygen was consumed. The O2 sensor will indicate too much oxygen, and this will trip a lean code.

B. If you have too much fuel, the exhaust air will still have way too much oxygen in it because there was no combustion, so no oxygen was consumed. The O2 sensor will indicate too much oxygen, and this will trip a lean code.

C. If you have not enough fuel, the exhaust air will still have way too much oxygen in it because there was no combustion, so no oxygen was consumed. The O2 sensor will indicate too much oxygen, and this will trip a lean code.

It seems to be that the concept that you are not understanding is that the whole system assumes that combustion happens. If it doesn't then the system is fooled. It can only see how much oxygen is left in the exhaust. In fact, worst than that, it can only see if there is too much oxygen, or too little oxygen. It can't sense how much too much or how much too little if it is way out of normal operational bounds.

shorod
03-13-2012, 04:01 PM
A large part of my hang up is that on 3 separate occasions I had a single coil pack fail on my '98 SHO and in all three cases I was able to monitor the lean and rich reports and STFT numbers in the datastream as well as the individual cylinder counts and correctly identify a faulty ignition coil (CoP system like the LS) before the CEL ever illuminated since the misfire counts were below the threshhold but I could feel them. So I've successfully seen (granted, small sample size) the lack of spark due to a faulty ignition coil cause a lean indication on the corresponding cylinder bank. I've witnessed this, but have not witnessed a faulty ignition coil cause a lean condition, so it's difficult for my head to grasp how such a reverse logic failure could occur. I WANT to believe the diagnostics work.

I understand the points you make above, but suspect that maybe there is some other element that would make it unlikely to get a lean indication due to a faulty ignition coil. I did a bit a web surfing last night looking for clearly documented cases of how this could happen, but didn't find anything.

I'm in learning mode here, but my first hand experience is clouding my willingness to accept this is a likely scenario. In the interest of not trying to further hijack Tabby's thread, I may pose this question to the Engineering and Technical forum.

-Rod

shorod
03-16-2012, 11:38 PM
So I now have another data point (http://www.automotiveforums.com/vbulletin/showthread.php?t=1076594) in your favor, Joegr.

-Rod

tabby24
03-23-2012, 11:16 AM
Codes for a lean system on both banks is not consistent with gas coming out of the tail pipe. If it truly is unburned fuel coming out though, that could explain the P0430 code as the converter will overheat and start to melt down internally if it runs too long with that much fuel coming through.

I would suggest you start by determining why you have the P1112 code since an Intake Air Temperature (IAT) sensor that is giving bogus readings could cause problems with the air/fuel ratio. I'd also suggest you check the fuel pressure and pick up a vacuum gauge and see what your vacuum is doing. Since your LS has the V6, and it's very common for the PCV elbow to fail which would help explain the lean codes, I think you have a nasty vacuum leak causing your driveability concerns.

-Rod
Thank you for your help. Im now going to have the pcv replaced. Do you know where I can get the hose pcv elbow and the valve? Or the part numbers? I can only find the hose and valve in store and online but no luck with the elbow. Would there be another name for this? I would prefer to go to the store to get these if you know of an autoparts store that carries them

shorod
03-23-2012, 02:54 PM
I'm not sure what the part number is for the "correct" PCV elbow and tube kit. The elbow is not sold by itself, it comes as part of a kit that also includes the rigid tubes. When I stopped by the local dealer looking for a replacement they could order the kit, but they sized up the elbow with what they had on their shelves and came up with a stand-alone elbow that is labeled as a "Connector" with Ford part number YL8Z-6A614-AA. The dealer said it is for a V8 Ford truck, but it saves a few bucks over the entire PCV hose kit by application for the LS, and my local dealer had it in stock.

-Rod

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