Dgoude Posted October 9, 2008 Share Posted October 9, 2008 Went to Advanced Auto yesterday and had them run a diagnostics check. It showed up as "lean" which the guy said he's been confused on. Some people say it's an air leak, some people say it's the 02 sensors and some say it just needs a tune up. Anyone have any more info on that? Quote Link to comment Share on other sites More sharing options...
George_Jetson Posted October 10, 2008 Share Posted October 10, 2008 First I would take it to another store and have them read the code and let us know what the number is. Lean conditions can be caused by vac leaks, first give the engine a good visual inspection, do not forget the pcv valve and hose (it's fairly well covered up and hard to see if you are not looking for it). Rubber hoses have a tendency to harden and crack over the years. The split hoses then cause vac leaks. Pay close attention to the hose that hooks the throttle body to the airflow meter. You do not indicate what year your car is. Do you have any other symtoms, such as a drop in mileage? That would be a good indication of the O2 sensor shorting out (which the computer would read as a lean condition). Quote Link to comment Share on other sites More sharing options...
SKperformance Posted October 10, 2008 Share Posted October 10, 2008 agreed , lean is too vague. Quote Link to comment Share on other sites More sharing options...
Dgoude Posted October 10, 2008 Author Share Posted October 10, 2008 agreed , lean is too vague. Sorry I didn't put year. I have a 99 ES300. Oddly enough the Check Engine, VSC and VSC OFF lights all come on at the same time. (More details about this below the update) ****UPDATE**** Went to Auto Zone and here is the Code that they came back with... Troubleshooting Code: PO171 OEM Brand: Domestic Definition - Fuel trim bank one condition Explanation - The powertrain control module uses the oxygen sensor to calculate air/fuel ratio of the engine. The computer has recognized a rich or lean condition on one engine bank only. Probably causes... 1. If bank one and two codes set together suspect fuel pressure or MAF (Mass Air Flow) Sensor 2. Oxygen sensor defective 3. Ignition misfire - repair 4. Fuel Injector problem **** Maybe this will help explain a little more so someone can help me diagnose correctly the first try! Before I replaced the battery terminals I had a bad connection that made me have to go and jiggle the terminals every once and a while to get them to connect and get juice flowing again. Every time that happened it reset the Check Engine light. So when I would get on the road again and hit the interstate and accel quickly, the first thing that would happen is my VSC and VSC OFF lights would come on. Then I would reach my destination and turn the car off. The next time I drove it, without fail, if I had to accelerate again, the Check Engine light comes on with the VSC and VSC OFF lights. Quote Link to comment Share on other sites More sharing options...
George_Jetson Posted October 11, 2008 Share Posted October 11, 2008 I looked up the code, alldata has the same code description, except for the missfire. So start by checking all vac hoses for cracking (especially the intake, between the throttle body and airflow sensor). Do you have any idea when the last time the fuel filter was changed? They also mentioned clogged injector and engine coolant sensor. It takes speciallized tools to check the injector, but you could test the temp sensor with a DVM. You could also just shotgun the temp sensor if it is not too expensive. The last thing they mention is the airflow meter itself, but that is not something you could test without a good scanner. Quote Link to comment Share on other sites More sharing options...
Dgoude Posted October 11, 2008 Author Share Posted October 11, 2008 I looked up the code, alldata has the same code description, except for the missfire. So start by checking all vac hoses for cracking (especially the intake, between the throttle body and airflow sensor). Do you have any idea when the last time the fuel filter was changed? They also mentioned clogged injector and engine coolant sensor. It takes speciallized tools to check the injector, but you could test the temp sensor with a DVM. You could also just shotgun the temp sensor if it is not too expensive. The last thing they mention is the airflow meter itself, but that is not something you could test without a good scanner. As far as I know the fuel filter hasn't been changed since I stopped going to Lexus for the services about 4 years ago. I've just started within the last year working on the car myself. Changed the brake pads and rotors, changed the spark plugs, and by accident had to change all of the "o" rings on the front fuel injectors. So bottom line is the only thing I know how to do on the list of things that you mentioned above is do a cursory check of the hoses. Did that today when I changed the oil and didn't see any visible cracks when checking from the top. So I guess I should take it to Lexus, have them diagnose the problem and then fix it myself if I can? Quote Link to comment Share on other sites More sharing options...
George_Jetson Posted October 11, 2008 Share Posted October 11, 2008 I would recommend taking it to a independant shop. Lexus dealer at best will overcharge you. The code you have can be read by any good professional scanner. My personel scanner is a snap on mt2500, gennisiss also makes a good scanner, unfortunatly both are too expensive for weekend mechanics. With a professional scanners you can read the code, and see engine information. Such as engine coolant temp (reads out in deg) lets you know in a second if the computer is reading the correct temp, (note quite often the instrument pannel temp gauge, and the computer temp gauge are totaly independent, one sensor could be working fine, the other could be dead). You could also read O2 sensor switching. You mentioned that you had to replace the injector o'rings, by any chance was that on the same bank that is now reading lean? If so did you lubricate the lower oring before inserting it into the intake manifold? Could you possibly have nicked a oring? Possibly you might have accidently caused a vac leak. Quote Link to comment Share on other sites More sharing options...
Dgoude Posted October 12, 2008 Author Share Posted October 12, 2008 I would recommend taking it to a independant shop. Lexus dealer at best will overcharge you. The code you have can be read by any good professional scanner. My personel scanner is a snap on mt2500, gennisiss also makes a good scanner, unfortunatly both are too expensive for weekend mechanics. With a professional scanners you can read the code, and see engine information. Such as engine coolant temp (reads out in deg) lets you know in a second if the computer is reading the correct temp, (note quite often the instrument pannel temp gauge, and the computer temp gauge are totaly independent, one sensor could be working fine, the other could be dead). You could also read O2 sensor switching. You mentioned that you had to replace the injector o'rings, by any chance was that on the same bank that is now reading lean? If so did you lubricate the lower oring before inserting it into the intake manifold? Could you possibly have nicked a oring? Possibly you might have accidently caused a vac leak. This was actually happening long before I had the incident with the injectors. I'm pretty sure I did everything correctly when putting those back together. So if I took it someplace like Christian Brothers they might be able to tell me exactly what the problem is instead of the ambiguous "lean" and 5 different possibilities that I got from Auto Zone? I really appreciate your help more than you know! Quote Link to comment Share on other sites More sharing options...
George_Jetson Posted October 12, 2008 Share Posted October 12, 2008 Yes, their scanners will be able to tell them what the engine coolant temp is reading in degs. That would eliminate right off. They could hook up a pressure gauge to eliminate the fuel pump. They can check the injector balence. And they can monitor the O2 sensors, (check to see if they are switching from rich to lean as they should be). Quote Link to comment Share on other sites More sharing options...
SKperformance Posted October 15, 2008 Share Posted October 15, 2008 Look for an exhaust leak as it can also cause a wrong indication on that bank , change the o2 sensor while you are at it. Lean means it is running hotter than it should be as the sensor it a temperature sensor. Quote Link to comment Share on other sites More sharing options...
George_Jetson Posted October 15, 2008 Share Posted October 15, 2008 Yes, a exhaust leak will cause a lean condition, the O2 sensor will pick up the oxygen and give a lean inidcation. But the O2 sensor doesn't detect temp, only oxygen. The sensor has to be hot before it starts to function. The first generation of 02 sensors had a single wire. O2 sensors found on OBD2 cars have 4 wires, two of the wires are for a internal heater. 12volts is applied to the heater to bring the sensors up to operating temp faster. Once the sensors are up to temp, and the engine coolant temp is up to operating range the computer can switch to closed loop operation. Quote Link to comment Share on other sites More sharing options...
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