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Topic Review (Newest First)
12-27-2003 08:22 AM
OhSueCQ
02 Sensor

I can't find the post I made earlier, so at the risk of looking stupid, I'll copy and paste it here to see if it shows up. Sorry if it gets posted twice.

Here it is:

I'm back. I did the check engine light flash sequence where you insert the key without starting the car and turn it on, off, on, off, on, and count the flashes. It gave me a code 51, which according to the computer code list I found on the internet for my car (94 Chrysler LHS) means that the oxygen sensor is stuck at lean position. I realize that if I've driven it this way for a while, it could have damaged the catalytic converter. But wouldn't I have noticed something if it's been this way for a while? And why does it always give you the # 12 code first (Memory Standby Power Loss - battery cable disconnected)? Is it because I initiated it by doing this procedure and that's the code you should get first? I checked it a few times and each time I had 1 flash, pause, 2 flashes, pause, 5 flashes, pause, 1 flash pause, 5 flashes, pause, 5 flashes pause.

I'm still taking my car to my mechanic, hopefully this week if he can work it in, but I'm trying to get a handle on repair costs, especially since I just finished with all the Christmas expense. How accurate is the key code procedure? How expensive are catalytic converters? Lastly, could some other malfunctioning part be causing this? Where is the 02 sensor located, is it easy to get to as in, can my hubby replace this part or are we better off just taking it in and hoping it doesn't lead into a lot of parts having to be replaced? I know that when the map sensor went out it was right on top, easy to get to and looked like I could even change that part myself.

Thanx for all of your input.

Sue

I found my post and the response. I'll study it.

Thanx,
Sue
12-27-2003 08:00 AM
dmorris1200 Hi Sue,

Ok, were going to try and get into this one. According to my Internet info, which is never as good as any professional tech manuals available at work, a code 51 means that the computer has maxed out it's fuel injector pulse to try and offset a lean condition. this is not the same as a code 21 that would indicate specifically that the O2 sensor is switching too slow or not at all. PCM's (Powertrain Control Modules) are programed with what we call 'adaptive strategies'. When a car is first started it operates in what we call 'open loop' meaning it is in 'non-feedback' operation using a preprogrammed set of values to operate. As the engine warms up she enters 'closed loop' operation and is now a 'feedback' system using inputs from several sensors to maintain a proper fuel/air ratio. The PCM is only programmed to either richen or lean out the mixture so far. It does this by changing the injector pulse and this can be seen by watching the long term fuel trim info on a scanner. Now lets say you develop a vacuum leak, the PCM will start to increase fuel trim to offset this. As the leak increases so does the fuel trim as the PCM keeps increasing fuel delivery to stabilize the air/fuel mixture. All PCM's are designed to adjust to a point and then a 'fault code' will be stored if that point is exceeded. This is most likely what happened to your car. The PCM saw the mixture leaning and kept increasing duel delivery until the 'fault code' was set. The million dollar question is 'why'? The O2 sensor could be going bad causing a 'false' input to the PCM making it richen the mixture, or you could have a vacuum leak that the PCM could not compensate for (broken vacuum hose, cracked intake gasket, etc.). This part of the diagnostic process is where some equipment and a little know-how is needed. To rule out the O2 sensor a tech would introduce something into the mixture to richen it and monitor the O2 sensors signal. If the sensor responds normally to the testing then we would start to look for vacuum leaks or other problems. This code as I explained above is a little more involved sometimes than some codes are. I'm not real familiar with the 3.5 engine but I have seen the Chrysler 3.3 V6 engines develop similar problems because of cracked intake plenum gaskets. As far as "where is the O2 sensor located", it is in the exhaust anywhere from the exhaust manifold to the cat. converter. It has to be before the converter since it measures the amount of oxygen in the exhaust pre-cat. It looks kind of like a spark plug in your exhaust with wires coming out of it. They make a special socket to remove/install them and often a little heat from a torch is required during removal. In approx. 1996 cars went to OBDII and added O2 sensors after the converters called 'downstream sensors' so the PCM could actually 'see' the difference between the gasses going into the converter and the gasses coming out of it. This finally allowed the PCM's to actually monitor whether or not the converters were working correctly or not. Whether or not you want to do a little 'guess' repairing is up to you. If the O2 sensor is in a decent place your husband may be able to rent the socket needed from your local auto parts store and replace it himself. My suggestion would be to get someone you trust in there to do a little more investigating before spending too much on unneeded parts. Hope this has helped, if something was missed asked again.

12-27-2003 06:37 AM
OhSueCQ
02 Sensor & E Check

I'm back. I did the check engine light flash sequence where you insert the key without starting the car and turn it on, off, on, off, on, and count the flashes. It gave me a code 51, which according to the computer code list I found on the internet for my car (94 Chrysler LHS) means that the oxygen sensor is stuck at lean position. I realize that if I've driven it this way for a while, it could have damaged the catalytic converter. But wouldn't I have noticed something if it's been this way for a while? And why does it always give you the # 12 code first (Memory Standby Power Loss - battery cable disconnected)? Is it because I initiated it by doing this procedure and that's the code you should get first? I checked it a few times and each time I had 1 flash, pause, 2 flashes, pause, 5 flashes, pause, 1 flash pause, 5 flashes, pause, 5 flashes pause.

I'm still taking my car to my mechanic, hopefully this week if he can work it in, but I'm trying to get a handle on repair costs, especially since I just finished with all the Christmas expense. How accurate is the key code procedure? How expensive are catalytic converters? Lastly, could some other malfunctioning part be causing this? Where is the 02 sensor located, is it easy to get to as in, can my hubby replace this part or are we better off just taking it in and hoping it doesn't lead into a lot of parts having to be replaced? I know that when the map sensor went out it was right on top, easy to get to and looked like I could even change that part myself.

Thanx for all of your input.

Sue
12-23-2003 10:25 AM
bluesman123 DMorris is right, Sue, your car is OBD-I. The O2 sensors are a very good guess. They get into a vicious cycle where they get lazy, the injectors run rich, the rich mixture makes them even lazier, and so on. I believe your model only has 1 sensor, its down by the collector. I don't believe they started putting one after the cat until a couple of years later, but you might check as they would both likely be cooked.

Good luck and Merry Xmas!

Bluesman
12-23-2003 06:01 AM
dmorris1200 Hi Sue, your car should be OBDI. Like 2-manytoyzs said it could be many things. Any sensor out of range could fool the computer into delivering the wrong amount of fuel. If the 'check engine' light came on there should be a code stored even after it shuts itself back off. As mentioned by 87442lover, a O2 sensor is a good guess (but still just a guess!). If she has high mileage the sensor could be what we call 'lazy' meaning she's cycling too slow. If your mechanic has a decent scanner he should be able to verify the sensors cycle rate. I would start with getting codes pulled and then look into your O2 sensor. Both good suggestions by the other members. The code check is important because even a bad coolant temp sensor could 'fool' the computer into thinking the engine is cold all the time and cause her to run rich.


12-23-2003 04:51 AM
87442lover Sue,

Your car is running real rich, replace the o2 sensor and try the test again. Something has to be telling the computer that the car needs more gas than it should be getting, this is usuall a faulty o2 sensor, and is also cheap to replace.
12-23-2003 04:38 AM
OhSueCQ
Map Sensor?

Thanx for your quick reply! The car as I said, runs great. I just got the E check yesterday and just noticed it was using a lot of gas a little bit later the same day (I know I wasn't having this gas useage problem prior to the E check). I've replaced 2 map sensors, one of them was replaced Aug 2001 and the other one July 2002 (it was under warranty). The only other problem I've ever had with this car is my check engine light has come on twice in the last 3 months. As soon as I shut the car off and restarted it, it stayed off and as I've said, there have been no other problems with the car, it runs like a dream. Come to think of it, the last time the map sensor went out - prior to that my check engine light came on a few times but went right back out and I didn't notice anything wrong with it until a month or so later when it was running really rough.

It had a full tune up and the works last October (2002), spark plug wires, the works. I've probably only put maybe 5000 miles on this car in the last year. I've changed the oil regularly but guess it's time for that again. And I'll have my mechanic replace the air cleaner when he does that (I replaced it last October too).

So could the map sensor alone be responsible for the failed HC and CO readings? The last time the map sensor went out, I thought something was wrong with my transmission because the car would barely go into reverse when I tried to back it out and it was running rough, I could barely get it to my mechanic. He serviced the transmission and as I said found that second bad map sensor. The time before when my map sensor went out the car wouldn't start at all. I'm wondering if the map sensor slowly goes bad and that's why the check engine light comes on sporadically but the car still runs? I do have a mechanic and thankfully he's the only mechanic that's ever worked on this car, he's going to check it out after the first of the year (I have until Feb 16 to pass the E check).

Again, thanx for your help, this is a great Forum.

Sue
12-23-2003 04:34 AM
87442lover
Re: Emissions HELP

Quote:
Originally posted by cutsupreme
I have an 85 cutlass supreme. This means I still have to pass the emissions test.

So of course I go to get my car inspected, safety passes fine but I fail emissions.
Does anyone know an easy way to lower the emission the car produces.
I went to a shop and the guy said it could be the timing chain, and that would be pretty expensive to fix.
Does anyone have any other ideas that can help me pass emissions.

Thanks for any input
Get an oil change, use some G2P formula or other de-carbonizer. Before you take it in for emissions drive the car for about half an hour. Also set the carb to run lean before they hook it up to the machine. Always works.
12-23-2003 12:10 AM
2-manytoyzs Lot of things could be wrong here Sue. Dont know if your car is OBDI or OBD II. Should be stated on the emission decal under the hood. Possible O2 sensor, high fuel pressure, MAP or MAF, ect. It can get expensive guessing at parts. Have the codes read and go from there........... I dont think its the EGR!
If this car has run with these kind of readings (rich) very long it could have damaged your cat.
BTW Don and Jmark - good discussion! I did smog check for 20 yrs here in Cal and I still dont completely understand all the ramifications and interactions of emission controls and testing. I smogged my Maxima today and the HC limit was 112 and I passed with 112.
12-22-2003 06:25 PM
OhSueCQ
Failed emissions test

I have a 94 Chrysler LHS and live in Ohio. I failed the Emissions test today on HC 200.5 (Limit 114.0) and CO 6.78 (Limit 0.63). Any suggestions as to what can be wrong? I just noticed today that my car seems to be using a lot of gas. It runs great, but has a little shakiness at idle sometimes.

Sue
10-14-2003 08:27 PM
Jmark Hi Don, no apology needed. I came on kinda strong too. Just wanted Cutsupreme to have a good shot at fixin the problem.

Hope to have more good conversations.
10-14-2003 07:54 PM
dmorris1200 Hey Jmark are you still checking in? After taking some time to sit back and re-read through the posts (especially your looong one) I have come to the conclusion that I owe you an apology. I will admit I really didn't take the time to thoroughly read through all the posts well enough initially but afterwards took the time to read through again. Aside from cutsupremes troubles after re-reading your posts I started re-thinking my EGR thoughts. I had originally formed the analogy that the EGR in a sense richened the mixture because I knew that the already burnt exhaust gasses lacked combustable oxygen, somewhere along the line someone must have worded it like that and I just never really analized it. After reading through what you wrote I guess you could say that technically the EGR doesn't really richen or lean out the mixture since as it's allowing less fresh air(oxygen) into the combustion chamber it is also allowing less fuel at the same time. The carb is still going to mix whatever ratio of fuel to air it is designed to do but the EGR just allows less of that mixture into the cylinders. Then I'm also thinking maybe at idle when we manually crank open the EGR we maybe aren't technically leaning her out as much as we are just totally depleating the cylinders of combustable gasses. What do you think???? I respect what you have to say or I would not have even wasted my time thinking this over and posting this reply. Maybe I should have read a little more thoroughly and typed a little less the other night but here we are and what's done is done. Hope you can accept this apology, Don.

10-13-2003 12:45 PM
Goldduster360 I had allot of experience with emissions problems when I had to get my 78 350 powered camaro to pass. It had a 600 CFM Holley with a 204-214 .420 .443 cam and single exhaust with converter still in place.

Usually all it took to pass was leaning out the mixture screws to the point it would ALMOST miss at an idle. Running the highest allowable idle seemed to help too, I always shot for around 850-900. I never had to retard the timing and it did not have egr in place. Always passed and they never did underhood checks, I lived in WPB, FL.

They always gave me some BS reason why it didn't pass if it didn't make the first pass. They once told me I needed new piston wrings or a carb overhaul. I pulled into the parking lot adusted the carb idle mixture a little leaner drove it back through and it passed, they didn't like it but oh well!
10-13-2003 08:27 AM
cutsupreme My engine was probably running 15 minutes prior to the test
10-12-2003 09:47 AM
dmorris1200
Quote:
Originally posted by Sean N
was the engine fully warmed up? The catalitic converters efficency is direclty related to the temperature..... A least that what my chemistry teacher tell us. He said his car failed when he just drove it to the shop to have tested. His mechanic told him to drive it for 30 minutes and try it again. sure enough he passed.
There is truth to your post Sean. Some people keep shutting their cars off and restarting them while waiting on line. This forces the computer to keep going from closed loop to open loop operation and doesn't allow the cat. converter to reach optimum temp. for catalist eficiency.


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