Co Mixture - odd dwell readings

[Jeff K]

Ok, I'm following the Co adjustment procedure as outlined in the pdf "CO Adjustments Tech Tips 11/10/08" by Dave Swingle.

My Stage 2 car gets horrible mileage (about 13-16) and I wanted to check the mixture.

I connect my dwell meter to the two leads of the frequency valve at the bulkhead connector. I removed the RPM relay and jumpered the two pins to make the relay buzz. It buzzes and I take the reading. I set the meter to 4 cylinder.

The nothing reading on the meter is 90,(actually 89.9) .. When I read it off the frequency valve it's supposed to be 45 consistently. Mine consistently says 83.5. I tried my analog dwell meter - same thing.

Anyone know what this means?

Thanks
Jeff

[DMCMW Dave]

[QUOTE=JeffKay;57258
Anyone know what this means?

Thanks
Jeff[/QUOTE]

Assuming the frequency valve is buzzing, it means your dwell meter can't read that signal. It seems that some meters are not sensistive enough. I've found that some meters work better than others, and I've even found a couple that will only read when connected backwards. (you have to invert the readings in your head, i.e. 55=45, 80=20).

I have also found that some meters will read at the diagnostic port even if they won't read at the frequency valve connector.

If you want to use the diagnostic port, put the meter probes into the rightmost two sockets closest to the rear of the car.

[Jeff K]

Assuming the frequency valve is buzzing, it means your dwell meter can't read that signal. It seems that some meters are not sensistive enough. I've found that some meters work better than others, and I've even found a couple that will only read when connected backwards. (you have to invert the readings in your head, i.e. 55=45, 80=20).

I have also found that some meters will read at the diagnostic port even if they won't read at the frequency valve connector.

If you want to use the diagnostic port, put the meter probes into the rightmost two sockets closest to the rear of the car.

Thanks - hey you wrote the article right? Cool!

Ummm, is the diag port the one dangling plug by the rear firewall? Would you have a pic or a link to a pic?

I have a white 2 pin open connector by the ballast resistor, and a 9 red pin open plug but the firewall connectors..

Thanks!
Jeff

[jawn101]

Sorry disregard my last post. The diagnostic connector is a square black one below the idle motor. It has a purple and an orange wire going to it. You may be missing the connector and just the wires could be left dangling. Use the orange one for one lead on your meter and ground the other lead.

[Jeff K]

Sorry disregard my last post. The diagnostic connector is a square black one below the idle motor. It has a purple and an orange wire going to it. You may be missing the connector and just the wires could be left dangling. Use the orange one for one lead on your meter and ground the other lead.

Thanks - I will try that tomorrow

[Bitsyncmaster]

Remember to press the WOT switch to test if our meter is hooked up backwards.

[Jeff K]

What Dwell meter do people have? Mine apparently is not sensitive enough to read the dwell off the frequency valve bulkhead connector. The one in the article is $170 now.. I'd hope for a less costly one.

Thanks!

[Blackie]

Can anyone please provide a link to Dave's article?

Cheers

[David T]

I have found that on many cars the ground terminal in the diagnostic plug is not grounded well. I use the one pin for the Lambda and connect the other wire to the motor for ground. I also have found not all meters work well on this signal. Before trying to take readings to adjust you always check what happens when you close the WOT switch and you can also ground the O2 sensor or apply 1.5 volts and note what readings you get. That way you can figure out if the Lamnda system and the meter are at least working, you may have a dead O2 sensor and will never be able to adjust the mixture properly. Remember to plug the housing after making an adjustment and let the motor settle for a moment before trying to take a reading. A TINY amount of adjustment makes a BIG difference so don't go cranking on that screw. You should not need more than 1/4 turn at most (usually a LOT less!). Note the initial position so if anything goes wrong at least you can put it back to where it was. You will know when you are in "closed loop", the meter will swing. In open loop it stays on one reading steady. You can only adjust in closed loop so if the meter is not swinging do NOT try to adjust.
David Teitelbaum




Can anyone please provide a link to Dave's article?

Cheers

[jawn101]

What Dwell meter do people have? Mine apparently is not sensitive enough to read the dwell off the frequency valve bulkhead connector. The one in the article is $170 now.. I'd hope for a less costly one.

Thanks!

I and many others have this one and it works great. Don't backprobe the bulkhead connector with it, use the orange wire at the diagnostic plug for the best readings. It has no 4 cyl scale so you'll have to double the 8 cyl readings but that's easy.

http://www.amazon.com/Actron-CP7605-Tachometer-Voltmeter-Analyzer/dp/B00062YUUS/ref=sr_1_1?ie=UTF8&qid=1337781934&sr=8-1

[jawn101]

I also noticed that when I plugged the mixture screw cap back on, it changed a bit.. probably because of the vacuum leak created by opening it.

I took a small rubber stopper that fit more or less into the hole for the CO plug and drilled a tiny hole straight through the center. Then I shoved my 3mm T handle hex wrench through it - that allowed me to adjust the CO without creating a leak around the wrench. Made adjustment a lot faster than when I was trying to do it, plug the hole, realize I'd gone too far, adjust again, etc.

[Jeff K]

I took a small rubber stopper that fit more or less into the hole for the CO plug and drilled a tiny hole straight through the center. Then I shoved my 3mm T handle hex wrench through it - that allowed me to adjust the CO without creating a leak around the wrench. Made adjustment a lot faster than when I was trying to do it, plug the hole, realize I'd gone too far, adjust again, etc.

Great idea.. thanks!

[Byrne H&A]

Experienced same excessively high NO reading at local emission test center. Emission test management allowed adjustment of CO and with increased setting, the NO value dropped to acceptable range.

[TTait]

Can anyone please provide a link to Dave's article?

Cheers

Bump - I'd appreciate seeing the full write up too... A search for "Dwell Meter" isn't turning it up.

[sdg3205]

I checked 3205s mixture today, just because I was curious. I found it sits at 50%, no matter where I put the meter. WOT puts it at 40%. The car seems to run beautifully.

If I reverse the meter polarity it just sits around 90% no matter what.

The FV buzzes but there is no audible oscillation. Am I in open loop? Too far out of whack for the lambda to correct?

http://youtu.be/mgFqOOIRd2U

I set it in 2010 with a dubious analogue meter.

[sdg3205]

I also checked meter on 2510. Wired backwards (and extrapolating backwards ie 70 = 30) and forwards and taking the reading from a variety of places yields very similar results which leads me to believe the meter is fine.

Backwards:
http://youtu.be/Gtx1OPtFNj4

And normally:
http://youtu.be/VH0mUtxfVFU

[sdg3205]

Anyone?

[Bitsyncmaster]

If you don't see a solid 60% (duty cylce) with WOT pressed then your meter is not working. Reversing the leads should read a solid 40%.

When your closed loop the reading will be swinging a good 20%. A solid 90% or solid 10% would suggest the mixture is set wrong and your open loop.

[sdg3205]

If you don't see a solid 60% (duty cylce) with WOT pressed then your meter is not working. Reversing the leads should read a solid 40%.

When your closed loop the reading will be swinging a good 20%. A solid 90% or solid 10% would suggest the mixture is set wrong and your open loop.

Yes I get the 40% with the WOT. As you can see from the videos i posted the meter works on 2510.

I get the feeling the mixture is either way too far off or the O2 sensor might be toast.

Should i re-crack the injectors to reset the baseline and go from there?

[Bitsyncmaster]

From what I saw, you seem to be adjusted pretty close. Since your meter reads backwards, your looking for reading 60 to 70% which would really be 30 to 40%.

[sdg3205]

From what I saw, you seem to be adjusted pretty close. Since your meter reads backwards, your looking for reading 60 to 70% which would really be 30 to 40%.

Yeah, thats on VIN 2510, which was where I verified my meter wasnt junk.

VIN 3205 is where Im having the trouble. it's the one that reads a steady 50 or 90 depending on how its hooked up.

[Bitsyncmaster]

Yeah, thats on VIN 2510, which was where I verified my meter wasnt junk.

VIN 3205 is where Im having the trouble. it's the one that reads a steady 50 or 90 depending on how its hooked up.

So when you reverse the meter leads the reading do not reverse as expected? Try connecting to the orange wire going to the diagnostic plug.

[sdg3205]

Exactly. On 2510 reversing the leads yields the expected backwards results. On 3205 if I have them one way it sits at 50 and 40 with the WOT. So when I switch them to what you'd think is the correct way I get 90. I've tried taking the reading from the FV plug at the bulkhead, the orange wire from the blue bulk head and using the block as a ground and also the back diagnostic port. All places yield the same readings.

[Bitsyncmaster]

Exactly. On 2510 reversing the leads yields the expected backwards results. On 3205 if I have them one way it sits at 50 and 40 with the WOT. So when I switch them to what you'd think is the correct way I get 90. I've tried taking the reading from the FV plug at the bulkhead, the orange wire from the blue bulk head and using the block as a ground and also the back diagnostic port. All places yield the same readings.

What it looks like is your getting noise using the FV on one car and the other car is better. So I think if you use the orange wire which does not have the inductive noise of the FV, you will get correct results with your meter.