failed the idle test at inspection (question)
12-21-2010, 03:57 PM
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failed the idle test at inspection (question)
everything passed fine at idle except the HC, it was at 657 and im only allowed 220.the CO was 0.17 and im allowed 1.2.
when he did the high idle test the HC went to 122 and the CO went to .37.both well within the tolerance.
what would cause it to be so bad at regular idle?
the engine is a 3.0 w about 50,000 miles on it.it was put in new by toyota several years ago.
i recently put a new exhaust on and had to replace both oxygen sensors to get the check eng lite to go out.(i scanned the codes)
when he did the high idle test the HC went to 122 and the CO went to .37.both well within the tolerance.
what would cause it to be so bad at regular idle?
the engine is a 3.0 w about 50,000 miles on it.it was put in new by toyota several years ago.
i recently put a new exhaust on and had to replace both oxygen sensors to get the check eng lite to go out.(i scanned the codes)
12-21-2010, 04:41 PM
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The most likely cause of high HC is running too rich. Since it may be mainly at idle (your 25mph HC isn't THAT low), I would look for misfire (does it idle smoothly) or a leaky injector (including the cold start injector). There are lots of causes, but I would look there first.
You can look at the output of the O2 sensor through the diagnostic connector. With TE1 grounded and the throttle off idle, VF1 flops from 0 to 5v in time with the O2 Sensor; it should flop about 8 times in 10 seconds. With TE1 open, VF1 has the "learned value" of the air fuel mixture. Nominally 2.5 volts, if it is less (0 or 1.25) it means the ECU is reducing fuel to compensate for a rich condition. If you have an A/F value of 0v, the ECU may be at the point where it can't "reduce" the fuel enough (meaning you have a leaky injector, etc.)
You can look at the output of the O2 sensor through the diagnostic connector. With TE1 grounded and the throttle off idle, VF1 flops from 0 to 5v in time with the O2 Sensor; it should flop about 8 times in 10 seconds. With TE1 open, VF1 has the "learned value" of the air fuel mixture. Nominally 2.5 volts, if it is less (0 or 1.25) it means the ECU is reducing fuel to compensate for a rich condition. If you have an A/F value of 0v, the ECU may be at the point where it can't "reduce" the fuel enough (meaning you have a leaky injector, etc.)
12-21-2010, 05:07 PM
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I had that exact same problem in my veezy where the higher rpm was fine but the idle was too-high HC. The cause turned out to be the tps that never grounded IDL to E2, which it is supposed to do when the throttle is closed (idle position). Sometimes the problem can be fixed by adjusting the position of the sensor. Either use the fsm instructions which require removing the TB to do properly: http://personal.utulsa.edu/~nathan-b...93throttle.pdf
Or use this technique from 4Crawler which doesn't require removing the TB: http://www.4crawler.com/4x4/CheapTricks/TPS/index.shtml
But if adjusting the tps doesn't get IDL to ground to E2, then you'll need a new tps to pass emissions. It made a world of difference on my truck.
Or use this technique from 4Crawler which doesn't require removing the TB: http://www.4crawler.com/4x4/CheapTricks/TPS/index.shtml
But if adjusting the tps doesn't get IDL to ground to E2, then you'll need a new tps to pass emissions. It made a world of difference on my truck.
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