I have read the procedure for adjusting mixture with a digital volt meter. When I attempt this, the meter won't hold anything close to a steady voltage. It jumps all over the place, making adjustment almost impossible. As described in the procedure, I'm monitoring the O2 sensor green (female) wire with the negative lead of the DVOM to ground. I'm tempted to bring home a scope from work and try it.

Has anyone dome this procedure?

Greg

 

Speaking of voltmeters, what brands of meters etc do you guys recommend, esp for the electical diagnosis? I go to auto supply and they have a great range in price. Home Depot has meters from 19.95 to 36.00. This DIY is struggling with dwell!

 

Are you disconnecting the O2 sensor from the fuel injection computer when you're trying to do the adjustment? If the sensor is connected, the computer will constantly adjust the mixture, and your meter will fluctuate up and down. You should have the sensor disconnected from the computer, and just have the meter hooked up to the sensor when you're adjusting.

 

Mike,

Yes, I have the sensor green lead disconnected and the meter probe in the female end wh1ch runs to the sensor. I also have a good ground source.

Greg

 

Greg:

I had the same experience. Some suggestions -

First, verify that the sensor is good and that all possible mixture-affecting items are working properly. I nearly drove myself nuts trying to adjust a rich condition with a marginal 02 sensor and malfunctioning temp sensor I.

Second, once sensors were good, I had reasonable success adjusting to an "average" point. I didn't get a steady reading either, but the differential became smaller and more acceptable I adjusted towards the correct voltage.

Seems to me that with the variables in an engine, even at idle, that getting a steady voltage is virtually impossible. Your scope idea may be a good one; a waveform would be a helluva lot easier than jumpin' voltage readings.

 

Thanks James, It is a brand new O2 sensor, brand new temp II sensor. I should check a few more things as well. Any suggestions? Still chasing the diesel commuter bus smell.

Thanks,
Greg

 

Greg - just for clarity, I was referring to the ever-hidden temp I, not II.

In my case, it's inside the AFM. In yours, I believe, it would be to check the operation of the hotwire in the MAF.

A thought - on my MY, the mixture adjustment is only for idle; off idle mixture is sensor controlled and fine-tuned by the 02 sensor.

I'm no LH-Jet guy, but if this holds true for you as well, maybe a wider search is in order - checking sensor input at the brain, checking injector function, air flow, etc. All the fun stuff.

Just my .928

 

FWIW, the proper way to adjust the mixture is to disconnect the O2 sensor, jumper the computer so it will not try to maintain the idle, hook up a exhaust analyzer to the two test pipes and then start the adjustment.

The ARM1 and the like are not going to be any good to you. I know, I have one and I'd never trust it to adjust mixture. But, it sure is pretty to watch.

Just my 2 cents.

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