contour running lean?

stanranger · 01-07-2008, 06:38 PM

I do not usually work on my girlfriends contour, mainly because it has been a good car. But recently the check engine light came and and she made a stop at auto zone to have the codes run. They told her the car was running too lean, and it could be numerous things. Im not sure where to start, are there any known problems with these cars running too lean. o2 sensors, MAF sensor.....any ideas? Also, this is a 1996 with the 4cyl. Thanks

jonmark1985 · 01-07-2008, 07:32 PM

Vacuum or intake leak, clogged injector, or a bad O2 sensor. Check for the vacuum leak first.

ABE · 01-07-2008, 07:55 PM

You need to get the code number i.e. P0123 since there are a very large number of codes covering "lean condition". With each code number is a very specific description that can be looked up in a few seconds. Does the check engine light stay on all the time or does it come and go. The code will provide a more specific area of investigation.

Does the car exhibit any drive ability issues, such as high idle speed, uneven idle, missing under acceleration, etc. Or is the car running just as good as always, but with the check engine light on.

We need more info to avoid sending you on a wild goose chase.

stanranger · 01-08-2008, 07:20 AM

Im sorry, i should of included more information in my first thread. The care does stall out when you are at a stop and you dont give it enough throttle to get moving. Basically to go from a dead stop you have to step hard on the throttle, if you just tap it to move real slow it will sputter a bit and stall out. This is obviously bad in heavy traffic, because of the speed and having to hit the pedal hard to go. Other then that it runs fine, maybe a bit worse gas millage then when she first got it but thats it. Ill will go with her next time to get the codes run, and ill write down exactly what the numbers are. But in the mean time i will check for vacuum leaks and the O2 sensors.

jonmark1985 · 01-08-2008, 07:57 AM

Sounds alot like a vacuum leak.

ABE · 01-08-2008, 10:14 AM

The fuel mileage may not be related if you live in a colder climate. The fuel has additional additives to cope with the cold and maintain drive ability and the engine uses more fuel to warm up with colder temperatures.

Is the off-idle problem restricted to a hot and slow idling engine or does it occur as well when the engine is cool but idling a bit faster than hot idle.

When the engine is at hot idle, I assume it is smooth and steady and the speed does not vary. Pull the electrical connector on the Intake Air Control (IAC) valve, it has a round body with a solenoid (and electrical connector) at the end. It is located on the throttle body. If the engine stalls you probably don't have a vacuum leak. So if engine runs it is using either a vacuum leak to get air or a bypass around the throttle plate in the throttle body. Some engines set a slow base idle on the throttle plate adjustment screw, which is supplemented by the PCM controlling the opening of the IAC to set idle speed.

If it stalls then take a look at the Throttle Position Sensor (TPS) which could have a bad segment at closed throttle delaying the info on an opening throttle to the PCM which in turn delays richening the mixture and the engine dies from lean mixture due to open throttle valve. The TPS is mounted on the throttle valve and has an electrical connector. Remove the connector and test the sensor with a digital ohm meter. As you open and then close the throttle the resistance should rise and fall uniformly. If there is a gap in the resistance you have a faulty TPS that will need to be replaced. A faulty TPS will set a transient code, check engine light will be on when PCM senses problem and off when it doesn't.

Hope this helps while you are waiting on codes to show up and be read.

stanranger · 01-12-2008, 04:17 PM

We took the car by autozone today and the code was PO171 .... Again the reader said,( Bank 1, lean). I think i saw on this forum befor that the PO171 was an o2 sensor, but im not 100%.

ABE · 01-13-2008, 04:23 PM

P0171 is system too lean bank 1. Bank 1 is the firewall side. Generally speaking this is not a sensor since the fuel trim monitor will adjust its setting and note the change in sensor readings i.e. sensor is not "flat-lining" as in a sensor problem. You have a vacuum leak or manifold gasket problem or similar.

Don't ignore or the PCM will adjust and flood the injectors and cat, and your bill will be CDN$1700 (don't ask me how I know).

jonmark1985 · 01-13-2008, 05:11 PM

[QUOTE=ABE;29570]P0171 is system too lean bank 1. Bank 1 is the firewall side. Generally speaking this is not a sensor since the fuel trim monitor will adjust its setting and note the change in sensor readings i.e. sensor is not "flat-lining" as in a sensor problem. You have a vacuum leak or manifold gasket problem or similar.

Don't ignore or the PCM will adjust and flood the injectors and cat, and your bill will be CDN$1700 (don't ask me how I know).[/QUOTE]

Don't forget that a lean burn can also destroy a piston!

stanranger · 01-13-2008, 05:14 PM

thank you for your response. I think this weekend i will spend trying to set the timing on my 87 2.9 ranger, and checking for vacuum leaks in the contour. I think im also going to check the mass air flow and clean that, and replace the throttle positioning sensor in the contour....see if i can smooth the idle on and stop it from stalling every now and again. Thanks again ABE, you've been great help.