I had auto zone scan the computer and found po171 and po174 "sys too lean". Has 75000 miles on it and I havnt change the o2 sensor yet. Should I check anything else first? Thanks!
2006-09-22 18:58:23 · 4 answers · asked by tony r 1 in Cars & Transportation ➔ Maintenance & Repairs
Check for a vacuum leak at the T shaped vacuum connector on the back of the throttle body. This is the T in the PCV system, that connects the PCV valve to the back of the throttle body. These will deteriorate and collapse on themselves and cause a hole to form in the T shaped rubber connector. If you are getting a lean code, I would check for a vacuum leak first. You may hear a hissing sound from the leak if you listen carefully with the hood raised.
Update: A loose fuel cap would cause a P0455 or Gross Evap leak, that is not your concern. The Evap system is not going to cause a lean code.
2006-09-22 19:05:13 · answer #1 · answered by yugie29 6 · 0⤊ 0⤋
What the scanner picked up was your oxygen sensor reading your engine running too lean. Oxygen sensors work by sensing how much oxygen is in your exhaust gasses. This, it turn, helps your computer regulate the fuel/air mixture going into you cylinders. If your fuel filter becomes clogged there won't be enough fuel getting into the mix tripping a lean code. If you have a vacuum leak in your system the same code will come up. If you have a leaking exhaust system, the oxygen sensor won't be able to pick up the amount of oxygen in the exhaust and will cause the computer to go to default tripping the lean code.
You first need to make sure you don't have an exhaust leak caused by holes in the tubing or a bad exhaust flange gasket. If you have changed the exhaust tubing to a too large of a size it will effect the system the same way as an exhaust leak. If your exhaust system hasn't been modified and there are no leaks, then you need to look for vacuum leaks. Get a can of starting fluid. With the engine running, spray the starting fluid around the vacuum hoses and at the base of the intake manifold. If the engine races you have found a vacuum leak and will know where to look to find it. If nothing happens and the engine doesn't change rpm, then you should change the fuel filter. Have the codes erased and drive it a while. If the check engine comes back on, then you might have to change the oxygen sensors. It sounds like a long drawn out process, but remember, it's better to find out exactly why the code was tripped then it is to throw money at it in the form of unneeded parts till it goes away. You don't want to go replacing parts that don't need replacing.
2006-09-23 02:18:11 · answer #2 · answered by Thomas S 3 · 0⤊ 0⤋
Sometimes you get that code just by having a loose or bad gas cap. Try checking the cap after you pour a fuel system cleaner in it. Then Clear the codes by disconnecting the battery for like 5 to 10 minutes. Drive it around and see if it goes away, if it doesn't, you might need to get some new oxygen sensors.
2006-09-23 02:05:54 · answer #3 · answered by Just a guy 2 · 0⤊ 0⤋
No you are on the right track.
2006-09-23 02:42:20 · answer #4 · answered by Anonymous · 0⤊ 0⤋