Any auto mechanics here?

[Danimal]

This is completely unrelated to motorcycles but this family is so helpful to others I thought I'd give it a shot. I have a 2001 ford focus zx3 (2 door hatchback). Its been missing at idle to the point where it will quit running once in awhile. Changed plugs, nothing. Changed wires, nothing. Changed ignition coil, nothing. When you start it it runs fine but once it warms up it acts up. For instance I get in car for work and drive 5 minutes. Stop at office to get paperwork and back out to car. Jump in drive another min. and then it starts this problem. Or I can start car and let it idle for ten minutes and it starts doing this. I just unplugged the oxygen sensor on the exhaust manifold and it ran rough for another two min. and then idled fine ever since. It's been doing so for at least 15 minutes now. So question number one. Does the oxygen sensor only tell computer when something wrong? Number two. If unplugged doesn't computer really think somethings wrong and turn a check engine light on or something? Thanks in advance.

[Guest tx2sturgis]

Your engine computer may be trying to compensate based on bad data from the sensor.

 

 

This is a copy and paste from Answers.com:

 

O2 sensor

 

Every new car, and most cars produced after 1980, have an oxygen sensor. The sensor is part of the emissions control system and feeds data to the engine management computer. The goal of the sensor is to help the engine run as efficiently as possible and also to produce as few emissions as possible.

A gasoline engine burns gasoline in the presence of oxygen. It turns out that there is a particular ratio of air and gasoline that is "perfect," and that ratio is 14.7:1 (different fuels have different perfect ratios -- the ratio depends on the amount of hydrogen and carbon found in a given amount of fuel). If there is less air than this perfect ratio, then there will be fuel left over after combustion. This is called a rich mixture. Rich mixtures are bad because the unburned fuel creates pollution. If there is more air than this perfect ratio, then there is excess oxygen. This is called a lean mixture. A lean mixture tends to produce more nitrogen-oxide pollutants, and, in some cases, it can cause poor performance and even engine damage.

The oxygen sensor is positioned in the exhaust pipe and can detect rich and lean mixtures. The mechanism in most sensors involves a chemical reaction that generates a voltage. The engine's computer looks at the voltage to determine if the mixture is rich or lean, and adjusts the amount of fuel entering the engine accordingly.

The reason why the engine needs the oxygen sensor is because the amount of oxygen that the engine can pull in depends on all sorts of things, such as the altitude, the temperature of the air, the temperature of the engine, the barometric pressure, the load on the engine, etc.

When the oxygen sensor fails, the computer can no longer sense the air/fuel ratio, so it ends up guessing. Your car performs poorly and uses more fuel than it needs to.

[utadventure]

I've had an ongoing problem with one of the three oxygen sensors that my 2000 Jimmy has. It keeps having the same one fail. Like you, we have just unplugged it for now.

 

The oxygen sensor sends continuous info to the cars main computer which uses the info to adjust the air/fuel mixture going to the cylinders. When mine fails, it continually sends that the system is to lean and the computer then enrichens the appropriate cylinders. With it unplugged, the computer uses a default to run the motor. It has hurt my mileage a little bit in the mean time but not nearly as bad as when it fails and the cost of the replacement.

 

Dave

[Sheradan]

Replace the sensors. Right now you are just "fooling" the car, but it will come up again later. It will never run the way it should until you do.

[Venturous Randy]

Have you had the system tested? If you have an Auto Zone close by, they will check it for free. There is also usually a test procedure where you can check your codes by counting the blinks on the check engine light, but you may need to get a repair book to do it.

Does your check engine light come on when you turn the ignition on before starting the car to make sure the bulb is even working?

RandyA

[Danimal]

So if the O2 sensor is bad it will cause the car to run poorly. And unplugging it will cause it to run normally again. Telling me that in fact it is that sensor thats bad. Right? Sorry I'm so not inclined mechanically. Thanks so much for the replys.

[bongobobny]

There are a few other normal maintenance items you may want to consider as well. First, when's the last time you changed the air filter? Try a new one for general operating conditions. Secondly, seeing as you only state an idle problem, the intake valve body throttle plate may be dirty and in need of some attention. While you have the air cleaner off for replacement, waste a can of valve body cleaner on the throttle plate. Just follow the instructions and see if that makes a diffference.

 

The O2 sensor may be getting flaky and giving erroneous info to the computer, but yes you would think it should trigger a code, but not always. They are a tad expensive, but after you do the intake service I mentioned, retry to sensor and see if you have the same symptoms or not.

 

Hey, a can of seafoam or similar will also clean up your fuel injectors which can also result in poor performance. It's always a good idea to add a can of injector cleaner every time you change the oil to keep the motor running smoothly...

[Wolf]

Chances are, if a O2 sensor keeps failing then you either have a bad cat, or your engine is running too rich which is fouling the sensor itself. By unplugging the sensor, you have created enough area for exhaust gases to escape the system there by letting it continue to run. You should have the exhaust system checked to be sure the cat is not the problem first, but, running with the sensor out of the exhaust can allow exhaust gases to enter your vehicle.

[Condor]

Just for the heck of it disconect the battery for about 15 minutes and then hook it back up again. When you first start the motor it won't idle to well, but after a few minutes the computor will reset itself and things will improve.... Sometimes the computor get's confoosed....

[Sheradan]

Chances are, if a O2 sensor keeps failing then you either have a bad cat, or your engine is running too rich which is fouling the sensor itself. By unplugging the sensor, you have created enough area for exhaust gases to escape the system there by letting it continue to run. You should have the exhaust system checked to be sure the cat is not the problem first, but, running with the sensor out of the exhaust can allow exhaust gases to enter your vehicle.

 

Acually a bad sensor will cause the computer to make run too rich, in turn CAUSING the cat to plug. The two problems usually go together if left un repaired.

[RedRider]

Another thing to look at is the crank sensor. My son's Saturn had the same issue once it got hot.

 

RR

[GeorgeS]

Have you considered a Plugged Fuel filter ?? Water in the Gas Tank ??

 

I would dump in a bottle of " HEET " before ripping and tearing into anything else.

 

Also, dump in a can of SEA-FOAM, or any other good Fuel Injector cleaner.

 

Might just be dirty fuel injectors, or plugged up Fuel Filter !!! I would deffinatly go there first !! Sea-Foam works for Cars also !! not just motorcycles

[jfoster]

My 08 Crown Vic did something like that...mine would surge at an idle and then die. It was it a bad throttle body. They replaced it and back to new. On mine it was obvious when you pulled the air intake off. The butterfly valve was partially open and would close, bad spring or something.

[jfoster]

Correction: On the throttle body butterfly valve, it would not close on its own.

[stvmaier]

Actually, unplugging the o2 sensor does more than eliminate the o2 signal... it puts the fuel system in "open loop" which makes it ignore alot of things(o2 being one). I'm not saying that you DONT have an o2 problem... but if you did, your check engine light would've come on (before you unplugged it) and you'd have a code like a P0171 or a P0172. You could have a Mass air flow sensor problem, which can go bad, but still be within parameters therefore NOT turning on the check engine light.... or even a vacuum leak. So I agree withe whoever said take it to Autozone and have them pull the codes for you... just remember that you WILL have a code set because you unplugged the O2 sensor.... good luck!

[Sideoftheroad]

Geesh. Wish I had been on this site over a year ago. I had a 2000(?) Ford Escort ZX2. Honestly I really liked it (even for a Ford IMO-I have not had good luck w/ Ford products) except for the engine issues. At times I could put the accelerator all the way down and the car would only go like 15 mph then all of a sudden it acted like it was catching up and then took off. Also it would jerk back and forth like someone just learning how to drive a stick and not using enough accelerator.

 

Took it to autozone they got the code from it. Then took it to the dealer to look at and told them. They tried to downplay what autozone could do. Just by pure coincidence (lol) the code the dealer came up w/ and the code that Autozone came up with were the same. Gee imagine that. I didn't let the dealer fix the car. Instead I got new plugs, new plug wires and a new coil pack. It worked just fine for I think about a year then it started acting up again.

 

Best I could figure is bad engine design. The coil pack was on top and towards the front so best guess was during rain (moisture I guess I should say) would kick back up towards the coil pack causing it to go bad?

 

Found a ZX2 forum and discovered this isn't an uncommon problem unfortunately. Got tired w/ dealing w/ the issue so I got rid of it. About a month before I got rid of it the automatic shifter started sticking too. It was an easy fix on my end, there was a little round hole on the floor console all you had to do was take the cover off and stick a screw driver down in there and whalla you can shift again. Not sure why the hole was there other than Ford must have known about the issue and decided to use a band aid as a fix. Found out later all I had to do was take out the floor console and clean up all the gunk underneath it around the shifter.

 

Also the 1st and only winter I had it, snow just started to fall, not much on the road, went over a small bridge, did a fishtail and a 180. Had a change my shorts after that one. Put some sand bags in the trunk and it did better after that.

 

Inexpensive nimble car with good fuel mileage but terrible engine issue. I just couldn't deal w/ it anymore so I got rid of it.

 

Here are a couple pics. Wondered if anyone ever did a double take due to my decal.

http://i215.photobucket.com/albums/cc121/lylejt/Other/ZX2/3ba7.jpg

http://i215.photobucket.com/albums/cc121/lylejt/Other/ZX2/175e.jpg

Edited October 28, 2009 by Sideoftheroad

[BradT]

Secondly, seeing as you only state an idle problem, the intake valve body throttle plate may be dirty and in need of some attention. While you have the air cleaner off for replacement, waste a can of valve body cleaner on the throttle plate.

Ford were bad for this. I always used a tooth brush and the cleaner to clean the seating surfaces of where the throttle plate closes.

 

Do this when ever you check the air filter or changing it.

 

BRad

[stvmaier]

the "hole" in the shifter is an emergency override of the shift interlock system, which, prevents you from shifting out of park unless your foot is ON the brake... actually... GOOD thinking on Ford's part (for a change)......