01 Prizm Code PO171

Sorry if this is off topic here. 01 Prizm, similar to 01 Corolla. Sluggish off idle when cold. Feels like it's lean and sets check engine light. Code is P0171. Manual gives a long list of items to check. Any idea where to start? Any common problems to check first?

Al

Reply to
Big Al
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The manual should list items to check in the likely order, that is, from most likely to least likely. If it is lean, also check the intake hose from the air flow meter to the throttle body.

Reply to
Ray O

Don't think that would make it lean only when first started, or could it? If it runs 15 to 30 seconds the problem gets better, after a few minutes it's gone. I'm trying to check the temp sensor. Like to find the SOB that designed the connector releases. Must have been laid off from designing child proof caps.

Al

Reply to
Big Al

Code P0171 means that the system is too lean (Bank 1). The Prism only has one bank.

A leak in the intake hose could cause the system to be too lean without setting other trouble codes. All you have to do is visually inspect the hose to see if it is cracked to eliminate it as a cause. When you first start the engine, the system runs open loop (using pre-programmed values) to determine how much air and fuel is needed for a given throttle position and coolant temperature. If there is a leak in the intake and too much air is entering the system, the engine would run poorly because more air is coming in than the system assumes is coming in. It takes about 15 to 30 seconds for the O2 sensor to heat up and begin functioning and the system to go to closed loop mode, where the system measures oxygen in the exhaust and adjusts the air/fuel mixture based on actual measurements. In this case, the system can compensate somewhat for a leak in the system.

Almost every connector in the vehicle has a release tab. Pop the tab with an awl or small screwdriver and it should come apart easily. Keep wrestling with the connection and you can cause another trouble code from a poor connection.

Reply to
Ray O

This car is not mine so I don't know its history. Looked at it today. Was trying to ID the temperature sensor when I noticed an oily film on the top of the intake duct. Looked at it and saw the MAF sensor and connector were oily. Removed the sensor, and the inside was full of oil. So I stuck my finger into the intake track and no oil. Some damned fool oiled the MAF sensor. Probably thought it was the throttle position sensor??? So I cleaned it up and put it back in. We'll see what happens tomorrow morning.

I would never pull on a connector without finding the release clip or whatever. The combination of where the connector is and what releases it sometimes is enough to make you want to work on 53 Buicks. My other pet peeve is the plastic fasteners we have to fight with.

Al

Reply to
Big Al

Aha! The truth comes out. Don't you know that any time you do a favor and work on a co-worker or friends car, anything simple will always be a roal PITA? I learned this many years ago yet a continue to fall for this axiom.

Wasn't sure what your experience was. I gave the warning about connectors in case you did not have much experience.

My handy dandy Snap-On plastic fastener taker offer is a marvelous investment. I only break about half of the fasteners I used to. I've seen similar tools at auto parts stores and Sears Hardware. My methodology on plastic fasteners - give it a gentle tug or poke to see what happens. If it doesn't release, wail on it, break the first one, figure out how it works, do the rest the right way, replace the one you broke later.

Reply to
Ray O

Have to admit, I have broken a few. One was on an injector harness on a 5.0 Mustang. The lock is external to the connector and replaceable. Except you have the buy the complete harness to get it:)

Al

Reply to
Big Al

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