I took my 84 to work not long ago. While driving home a fellow how works with me was in back of me at a light. The next day he said it smelled like your dumping raw fuel. What would cause the car to dump raw fuel? I checked for codes and all is normal. Could it be the O2 sensor?
My 84 has never gotton very good mileage on a gallon of fuel.

Any thoughts?

 

If your O2 sensor is not working properly and is sending a bad signal to your ECM that your engine is running lean, the ECM will tell the injectors to stay open longer and dump too much fuel into the engine, however this should throw a lean condition code.

If your O2 sensor is not working properly and sending a signal to the ECM that you have a correct mixture when in fact you have 1 or more injectors that are sticking open and dumping fuel, you will have a rich condition without a code. The O2 sensor could be just bad enough that the rich mixture makes it read within the correct range.

Is your exhaust pipes black from a rich mixture? if so you do have a rich mixture problem and you also probably have a bad O2 sensor and an injector that is sticking open.

My money is on a bad O2 sensor.

Test the O2 sensor first and replace it if necessary, if the new one then throws a code and the problem does not go away, you need to pull the injectors and test for sticking open.

Report back before buying any new parts and test all parts before replacing will save you a bunch of money.

Best regards
Jerris

 

yes, a skewed O2 will do this

 

I do recall one of the fellows from my previous job saying he could see black smoke coming from the pipes.

I'll test the O2 sensor first and then work from there.

Thank you

 

A rich mixture could also be caused by a bad ECT sensor, too. Don't throw parts at it, trouble shoot.

RACE ON!!!

 

Yes but if this was the reason instead of a bad O2 he would get a code 45 (rich exhaust indicated). He reported that there were no codes.
I would really like to know if there are any codes stored such as 45 (rich exhaust indicated) 13 or 63( O2 sensor circuit open ) or none as reported in his first post.
If there are none then the O2 sensor would appear to not be doing it's job and would need changing.
Pulling the codes as a first step in troubleshooting the O2 is the first step he needs to take as depending on the code, or lack thereof, we will know if the O2 sensor is working or not.
Jerris

 

I placed the car in diagnostic mode and received code 12's. I then placed the car in field service mode and it went into open loop for several minutes, then into closed loop for several minutes. After that the check engine light flashed pretty evenly between on and off. At one point the light would be on for about two seconds then off for two seconds, followed by the light being on for a second then off for a second. I had no real patten of the light being on longer then being off in order to determine open or closed loop. Not sure if it matters, but the car has not been stated in over a week.

 

I was just about to argue that it wouldn't set a rich code, because that rich mixture was being called for by the ECM with the cold temps a defective or disconnected ECT sensor would be reporting. But now I read that Brimis is reporting that it goes into closed loop. It couldn't go into closed loop with the ECM sensing the engine that cold.

Brimis,
Do some rereading. The frequency of the flashes tells you open or closed loop. Two or more flashes per second is open loop. One flash every second is closed loop. In closed loop, a quick flash (more off time than on time) indicates a lean mixture. The light will be on more of the one second interval when the mixture is rich. When the light is at the slower frequencies (one flash per second) and alternates between long and short flashes, the indication is pretty much a proper mixture. Based on what you've reported, I'd do a fuel pressure check. If some foreign material is partially blocking up the regulator, you may have excessive fuel pressure which would richen it up.

RACE ON!!!

 

Once again, if we both agree that there is a rich mixtere ( by whatever means you think it is being caused) and the O2 sensor does NOT cause the ECM to throw a rich mixture code ..... then the O2 sensor is NOT doing its job and needs to be replaced ( as the ECM is not throwing an open O2 sensor circuit code either so it is not a broken sensor wire).

I think we can saftly say Brimis has tested the O2 sensor and it is time to REPLACE it.

If there are other systems contributing to this rich condition besides the O2, at least a properly functioning O2 sensor will throw the appropiate code and we can begin to hunt for the second problem.

At this time, there is no evidence that there is anything wrong other than a bad O2 sensor ( or ECM, no evidence of this either) not telling the ECM the mixture is rich so that it can compensate with less fuel through the injectors.

We both advocate testing before replacing. This time I think Brimis has tested enough (unless he has a bad ECM that is carrying out all other functions except injector pulse regulation, which is highly unlikely)

Bremis, go buy the O2 sensor and enjoy either a rich mixture code or better gas milage. Your oroginal hunch appears correct and I am proud of the fact that you did some appropiate testing before simply changing parts on a hunch, even when the hunch turns out to be correct.

CFI-EFI, now repeat after me ............ Jerris is right LOL

Jerris

 

CFI-EFI,
When I initially started the car it immediately went into open loop, engine light flashing real fast, as in 2.5 times per seconds. After about 2 minutes the engine's RPM's slowed and the engine light slowed to about 1 time per second. This being my first experience, I now know the difference between open and closed loop readings. It wasn't until about 5 minutes with the engine running did I have a problem reading the code.

I'll put the car in field service mode in the morning and go for a short ride and try to read the engine light more closely after the car has been sufficiently warmed up.

Silly question, what if I just diconnect the O2 sensor wire? What code would I see?

The more I read my Helms, the better things fall into place. Is it just me or do you fellows have to read a section more then once in order to understand how something functions?

 

Early models have only one O2 sensor on drivers side. If Injector on passenger side stays open, O2 sensor won't see it. Check for leaking injectors before replacing O2 sensor. Been there, done that.

Larry

 

Jerris is right LOL.
There are some other factors that can come into play, especially on an '84, but I can't say that anything you've written is incorrect. We don't disagree.


LEAN. Code 48. Page 6E2-48, among others.
Often.

RACE ON!!!

 

See I knew you had a sense of humor.
You are also not incorrect, there are other things that can come into effect.......... after we replace the bad O2 sensor.
Best regards
Jerris

 

I must admit, you 2 guys make great reading while most try to stay out of your line of fire.

 

it could also be the temp sendi g unit

 

This thread is seventeen years old. Time to move on.