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Dirty, lying error codes. Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Fri, 5 Sep 2003 11:01:11
In Reply to: Although this is lengthy, PLEASE read for info>>>, Joe98, Thu, 4 Sep 2003 14:21:07 Members do not see ads below this line. - Help Keep This Site Online - Signup |
Fault codes should be taken with a grain of salt and a shot of tequila. The ECU is not sophisticated enough to isolate the fault to the sensor. Really. It's very, very hard. I work on self-diagnostic systems for aerospace, and with significantly more powerful processing, we haven't licked the mis-isolation problem.
The fault code isn't useless, it's just not a maintenance action. The fault code says that the O2 sensor is reading off scale. Now, that could be because of a bad sensor. Or, it could be because the wire from the sensor to the ECU is bad. Or, The Sensor Could be Telling The Truth! The sensor could be stuck at 0.2 volts all the time, and the ECU figures it must be broken. But it could also be that there is a problem that's causing the engine to run rich. The ECU can't detect that, so it blames the sensor.
So yes, a O2 sensor code can very well be not the sensor. In fact, I'd assume it wasn't the sensor.
Rarely, if ever, will you hear a vacuum leak. Engines make way too much noise, and it doesn't take much of a leak to screw things up.
My guess is that the ECU is seeing something it doesn't like, and is limiting you to base boost.
Step one is to figure out if you're running rich or lean. How do the spark plugs look? Stick a voltmeter on the #1 O2 sensor output and look at it - is it swinging around 0.5 volts like it should, or is it stuck at 0.2 or 0.9 volts?
If you're running lean, look for vacuum leaks. My favorite leak on a Turbo is at the charcoal canister. The turbo (especially modified ones with higher boost) likes to blow the hoses off the canister. Since it's buried in the right front fender, you can't see it. Remove the right front turn signal assembly (easy) and peek in. Make sure the hoses are all in place. Also - if you're running lean, perhaps it's the Fuel Filter. Yes, it's new. Perhaps a spider built a nest in it while it was sitting around. Perhaps it's defective, and the element collapsed and the internal pressure drop is high enough to limit fuel flow. To check that, you'd need to measure fuel delivery.
If you're running rich, suspect the Fuel Pressure Regulator.
Is this the total set of possible problems? No - there can be a lot. But step one is to see if you're running rich or lean. Then find out why.
posted by 192.249....
, Fri, 5 Sep 2003 11:01:11 <-- Viewing This Message, Fri, 5 Sep 2003 20:54:50, Thu, 4 Sep 2003 08:37:56, Fri, 5 Sep 2003 10:48:44, Thu, 4 Sep 2003 11:43:39
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