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Re: AC Compressor Noisy & O2 Sensor Posted by Ari [Email] ![]() ![]() In Reply to: AC Compressor Noisy & O2 Sensor, Yaofeng, Mon, 13 Jan 2003 08:48:02 Members do not see ads below this line. - Help Keep This Site Online - Signup |
What, specifically, failed in the emissions test?
Typically, high NOx is due to high combustion temperatures. That can be due to running lean. Lean running can be a bad O2 sensor, but it can also be a vacuum leak, low fuel pressure (fuel pump, fuel filter, or most likely, FPR), and a few other things. High CO or high Hydrocarbons can be due to rich running, which could be O2 sensor, but again can be a bad FPR, flakey MAP sensor, etc.
Of course, you should always check the plugs, because they tell you what's going on in the engine. PUll them and check the condition and gap, but are they stark white (lean running), fluffy black (very rich), covered with fused material (knocking)? They should be a nice light grey.
So - what were the numbers, and how do your plugs look?
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