97 Celica P0172

[paulcalif]

I am purchasing a 97 Celica with 156K miles. The car is in really good condition, but the check engine light is on and gives p0172. I looked at the engine and it looks like the O2 sensor has been replaced and there is a new hose clamp up by the MAF - so I am guessing that the MAF has at least been cleaned. I found one other post here about the p0172 error and it said to check and clean the MAF first, which I'll do. There were some other suggestions, but I'd never heard of them before. Something about long term fuel something or other. Can someone explain what that is and how to test? Plus any additional info. I'm getting the car at a great price, but I need to get it smogged quickly, so this needs to get resolved right away. I will be watching for your replies and will keep you updated on what I do. I have been a back yard mechanic for many years, so I should be able to do anything you guys advise, with a little instruction.

Thanks - Paul

[paulcalif]

I have learned a few things.

1. It can't be the MAF because this model doesn't have one.
2. The spark plugs are new
3. The O2 Sensor appears to be new
4. I pulled the throttle body and cleaned it, plus I ISCV (idle speed contol valve), it was pretty dirty.
5. The intake manifold had a lot of slimey carbon - thought that was kind of weird.
6. The air filter was in wrong with the gasket pinched. Could have been sucking dirty air? Put a new filter in the right way.

I could really use some help from you guys, no one has replied yet.

This is the 2.2 engine and it's a GT
The code p0172 is rich bank 1.

I believe bank 1 means the o2 sensor before the cat, is that right?

Having checked the 02 sensor and finding it looking almost new with a very slight grey coating, it doesn't look like it's been running rich.

So, I ask myself, what could cause the 02 sensor to report a rich condition?

1. faulty 02 sensor (but it appears new).
2. Actually running rich - but why? Seems to run pretty good. Not smoking.
3. The ECU is bad, and everything else is fine.
4. The Catalitic Converter is clogging and not allowing the exhaust to flow well, which would back it up in the exhaust manifold where the O2 sensor might find it too rich???? Just a guess.

I am leaning towards the ECU. I'm thinking that I need to check the O2 sensor while driving the car. Anyone know how to do that? I think I can just connect a volt meter to it and look to see if it's putting out .9 volts too often?

I am quickly running out of time on this, any ideas would be greatly appreciated -

I have a Haynes manual coming in the mail, but in the mean time, does anyone know where I can get a PDF of it? Or, can you tell me where the ECU on this car is located?

Please help me out, thanks!!!

[hatchy_gt-s]

Bank 1 just means which side of the motor the sensor is on. ie a v6 has 2 heads meaning 2 sensors.
The carbon in your intake is from the EGR(exhaust gas return). I would check this for proper working. If stuck open the O2 sensor would read rich.
Rarely is it an O2 sensor when a code comes up for rich/lean.
If rich it means to much fuel is entering or not enough air. Seeing as you said the filter was in wrong I would check the air intake.
Another thing to look for are vacuum leaks, they too can cause rich fuel mixture.