Actron Dwell Meter and Idle Hunting

[DrWin]

So, I was looking at this video:
https://www.youtube.com/watch?v=HKT_i82VtIo

I bought an Actron Dwell Meter (not excactly the same model) and tried doing what Chris is doing in the video. It cured my idle hunting by just adjusting the Fuel/Air mixture by a little bit. I connected to the meter at the same spots Chris is doing on the video, but I'm getting a different result:

During Warmup: (Steady, not fluctuating, RPM steady)
DSC_0370.jpg

After Warmup: (Steady, not fluctuating, RPM varies a little)
DSC_0372.jpg

I don't get it, why isn't the needle moving when I can hear the RPMs rise and fall?
I understand that the meter isn't monitoring RPMs directly, but I was also under the impression that the output to the diagnostic plug would/should fluctuate?

Bonus question - why are we supposed to look at the 8 cylinder gauge for a 6 cyl car?

Edit:
This is what it looks like when it isnt powered:
DSC_0374.jpg

[MrChocky]

Bonus question - why are we supposed to look at the 8 cylinder gauge for a 6 cyl car?
DSC_0374.jpg

Cos it's a sorta cut down V8:

https://en.wikipedia.org/wiki/V6_PRV_engine

"The PRV engine could be seen as a V8 with two missing cylinders, having a 90-degree angle between cylinder banks, rather than the customary 60, but with crankpins being 120 degrees apart. The Maserati V6 of the Citroën SM followed a remarkably similar pattern of development."

Now I know why!

[Michael]

Cos it's a sorta cut down V8:

https://en.wikipedia.org/wiki/V6_PRV_engine

"The PRV engine could be seen as a V8 with two missing cylinders, having a 90-degree angle between cylinder banks, rather than the customary 60, but with crankpins being 120 degrees apart. The Maserati V6 of the Citroën SM followed a remarkably similar pattern of development."

Now I know why!

No not exactly. The manual uses 4cly readings for more accuracy since we are adjusting mixture based off of ignition. You use the 8cyl scale and double it.

That aside, some cars have a simple 2 spade connector with a purple and orange wire instead of the diagnostic port. (use the orange for your signal wire) and ground properly of course. Once in closed loop you should see some movement of needle indicating the o2 sensor is operating. No movement means something is wrong with the o2 signal(bad or dirty sensor, broken wire, Frequency valve, etc.). O2 sensors are cheap and easy to replace and if you don't know when it was done last, replace it anyway. I would recommend getting a Bosch because the price is negligible (around 30-40 bucks) the probe on a good sensor will heat up faster and offer quicker correction vs. a cheap generic o2 sensor. I compared a Dgo sensor and a Bosch sensor from DeLorean Industries side by side and the difference was obvious.

Also make sure your idle circuit is functioning properly. Start by checking the micro switch engagement.

[Bitsyncmaster]

Your mixture is adjusted wrong with it sitting at that low value.

Yes adjusting like that will stop hunting because the lambda is not changing the mixture.

The 4 cylinder was chosen because that lets your read out the dwell values more accurately. It's just displaying the duty cycle on a dwell scale.

You want to adjust your mixture again to get an average 30 to 40 deg. for a 4 cylinder dwell scale.

[Acmetowers]

I've just had to fix this issue with idle hunting and bad emissions. I'd say before you start adjusting the CO check your timing and fuel pressures. My vehicle failed its emissions >9.99% CO HC 674ppm on its annual check. The car was 2 degrees out on timing, system pressure was half a bar too low and control pressure .7 bar too high, after these were sorted I then adjusted the CO (about a full turn) to get the dwell around 35-45 on the 4 cylinder setting. After this C0 was 0.03% and HC 235ppm. Basically make sure your fuel and timing are right before setting the dwell (CO). Also don't buy one of those Chinese red boxed fuel pressure testers they're only suitable as landfill.

[DrWin]

I've just had to fix this issue with idle hunting and bad emissions. I'd say before you start adjusting the CO check your timing and fuel pressures. My vehicle failed its emissions >9.99% CO HC 674ppm on its annual check. The car was 2 degrees out on timing, system pressure was half a bar too low and control pressure .7 bar too high, after these were sorted I then adjusted the CO (about a full turn) to get the dwell around 35-45 on the 4 cylinder setting. After this C0 was 0.03% and HC 235ppm. Basically make sure your fuel and timing are right before setting the dwell (CO). Also don't buy one of those Chinese red boxed fuel pressure testers they're only suitable as landfill.

Thanks, that's good to know. Care to recommend a suitable (quality) fuel pressure tester?

[DrWin]

Your mixture is adjusted wrong with it sitting at that low value.

Yes adjusting like that will stop hunting because the lambda is not changing the mixture.

The 4 cylinder was chosen because that lets your read out the dwell values more accurately. It's just displaying the duty cycle on a dwell scale.

You want to adjust your mixture again to get an average 30 to 40 deg. for a 4 cylinder dwell scale.

Right, I see that. So I'm gonna try to get the needle moving again by replacing the O2 sensor, and the trying to get the mixture set to hit between 30 - 40 deg. on the 4 cylinder dwell scale (15-20 on the 8 cyl.).

[Ron]

Doc, I don't know where the "15°" is coming from unless it is because a lot of people like to run it rich, but the manual says "35-45° (reading pulsates)" swinging, so it should swing across 40°, which is 20° on eight cylinder scale.
The specs also calls for the engine to be fully warm, pipes hot, etc., not right after coming out of "closed loop", as in the video. (After a drive, to also clean the plugs etc, is good.)
The RPM is supposed to be temporarily set to 950 during the procedure.
And, being picky, the meter's ground should be connected to the ground reference connection at the right rear air horn (Blue).
I agree with Acmetowers, as the manual says that all base settings should be checked before setting the CO. (See D:04:01-05)

Since your reading looks close cold ("50-60, steady") and showing ~4° when warm (low/lean), it may be so far off that you haven't been turning it enough to matter, as Bitsy mentioned (common mistake). So, you might try the following (before/while you wait on your goodies):
First, keep track of where the screw is now ( just in case ;-).
Remember turning CW=Right=Richer and turning CCW=Left=Lean. (Needle works opposite!)
Turn the screw sloooowly to the right in increments to get it down to swinging across 20°.
Once you get it close, a little goes a long ways (very touchy to get exact).
Don't forget to plug the hole and wait a few seconds before taking a reading.

[DrWin]

No not exactly. The manual uses 4cly readings for more accuracy since we are adjusting mixture based off of ignition. You use the 8cyl scale and double it.

That aside, some cars have a simple 2 spade connector with a purple and orange wire instead of the diagnostic port. (use the orange for your signal wire) and ground properly of course. Once in closed loop you should see some movement of needle indicating the o2 sensor is operating. No movement means something is wrong with the o2 signal(bad or dirty sensor, broken wire, Frequency valve, etc.). O2 sensors are cheap and easy to replace and if you don't know when it was done last, replace it anyway. I would recommend getting a Bosch because the price is negligible (around 30-40 bucks) the probe on a good sensor will heat up faster and offer quicker correction vs. a cheap generic o2 sensor. I compared a Dgo sensor and a Bosch sensor from DeLorean Industries side by side and the difference was obvious.

Also make sure your idle circuit is functioning properly. Start by checking the micro switch engagement.

Yeah, I have the 2 spade connector setup, and took care to connect/ground properly. I think I'll try to change out the O2 sensor like you suggested. I suspect that hasn't been done in quite a while. I have a generic one sitting on the shelf, but I'd rather try the Bosch one, now that you recommend it, if I can find one.

[FABombjoy]

Bonus question - why are we supposed to look at the 8 cylinder gauge for a 6 cyl car?

Because you aren't measuring ignition dwell, rather repurposing a "available in every corner drugstore in 1981" ignition dwell meter to measure the duty cycle on the frequency valve. The oddball settings best match the measurement needs w/ greatest resolution.

Now its easy to buy a multimeter with duty cycle measurement which can also be used, you just have to rescale the manual's from 0-90 degree values to 0-100 percent.

In my brief stint with K-jet turbo, I had an external logging box that did just this, so I could ensure that open-loop modes were triggered properly under boost.