Actron Dwell Meter - how to tell if it's working correctly? Worse after adjustments

[dean2526]

I got one on ebay and it seems to work, the needle moves and I set the dwell between 15-20. However, on cold start this morning the car is atrocious (it was cooler than normal, but low 60 degrees is not cold-Im in FL). I will say when adjusting it, it was not swinging much (like between 17-19). Some of the videos I have seen show the swings of 7-9 points. The car starts real rough and then stalls. I can rev it up but then stalls. Thoughts? I dont know if the dwell meter is broken or what.

[Bitsyncmaster]

I got one on ebay and it seems to work, the needle moves and I set the dwell between 15-20. However, on cold start this morning the car is atrocious (it was cooler than normal, but low 60 degrees is not cold-Im in FL). I will say when adjusting it, it was not swinging much (like between 17-19). Some of the videos I have seen show the swings of 7-9 points. The car starts real rough and then stalls. I can rev it up but then stalls. Thoughts? I dont know if the dwell meter is broken or what.

A cold engine it should read a solid 45 deg. You can adjust your meter to show that value.

[dean2526]

A cold engine it should read a solid 45 deg. You can adjust your meter to show that value.

I'm a newbie to this, how do I adjust/calibrate the meter?

[bytes311]

You only make the mixture adjustment on a fully warmed engine (cooling fans cycled at least twice). Of course, everything else in the system needs to be functioning correctly before you touch that.

When you connect your dwell meter on a cold engine, the needle should stay fixed and not oscillate until the O2 sensor heats up. It will only start oscillating if your mixture is within the ECU's control range. If it's out of range, you won't see any activity. Do you hear the frequency valve buzzing loudly on the passenger side valve cover while the engine's running?

[dean2526]

You only make the mixture adjustment on a fully warmed engine (cooling fans cycled at least twice). Of course, everything else in the system needs to be functioning correctly before you touch that.

When you connect your dwell meter on a cold engine, the needle should stay fixed and not oscillate until the O2 sensor heats up. It will only start oscillating if your mixture is within the ECU's control range. If it's out of range, you won't see any activity. Do you hear the frequency valve buzzing loudly on the passenger side valve cover while the engine's running?


Yes, I followed the DeLoreanTECH procedure from YouTube and only did the adjustments once engine was warm. I don't know about the frequency valve buzzing, I can look into that Saturday when I try it again. From the videos I have seen the swing was from like 12-22 (10 units), my swing was very small, like 16-19 (3 units). I don't know if the Actron is not working correctly or what. Something is off because the car runs so bad, I wish I wouldn't have even touched it :) It was rough and sluggish when cold before, now it's undrivable.

[bytes311]

Yes, I followed the DeLoreanTECH procedure from YouTube and only did the adjustments once engine was warm. I don't know about the frequency valve buzzing, I can look into that Saturday when I try it again. From the videos I have seen the swing was from like 12-22 (10 units), my swing was very small, like 16-19 (3 units). I don't know if the Actron is not working correctly or what. Something is off because the car runs so bad, I wish I wouldn't have even touched it :) It was rough and sluggish when cold before, now it's undrivable.

When was the last time it was serviced (new plugs, plug wires, cap+rotor, o2 sensor)? If your meter oscillates, it's working. You may just need a basic tune-up!

[dean2526]

When was the last time it was serviced (new plugs, plug wires, cap+rotor, o2 sensor)? If your meter oscillates, it's working. You may just need a basic tune-up!

I got it from Orlando DMC in May, so it was all good to go (and they have been helping me, I lost the CO2 plug, so that was an issue). I don't want to have to go back to Orlando for service, so I was trying to do it myself. :) So my point is, everything else should be good to go, if I can dial in the fuel/air mixture.

[Bitsyncmaster]

I'm a newbie to this, how do I adjust/calibrate the meter?

I'm assuming your dial has a zero screw adjustment. My dwell is digital so I don't have your model.

[bytes311]

I got it from Orlando DMC in May, so it was all good to go (and they have been helping me, I lost the CO2 plug, so that was an issue). I don't want to have to go back to Orlando for service, so I was trying to do it myself. :) So my point is, everything else should be good to go, if I can dial in the fuel/air mixture.

Gotcha! The mixture is fixed at 14.7 AFR. The purpose of the adjustment screw isn't to change that, it's to center the lambda system within its minimum and maximum control range.

As long as your meter is swinging back and forth, and you don't hear the frequency valve cutting in and out as it reaches the min or max of its control range, you're in a good spot, as far as that goes.

[David T]

Gotcha! The mixture is fixed at 14.7 AFR. The purpose of the adjustment screw isn't to change that, it's to center the lambda system within its minimum and maximum control range.

As long as your meter is swinging back and forth, and you don't hear the frequency valve cutting in and out as it reaches the min or max of its control range, you're in a good spot, as far as that goes.

Before you even think of touching that mixture screw you must make sure EVERYTHING is PERFECT! No vacuum leaks, good O2 sensor, all of the injectors opening and closing properly and good spray patterns, clean and gapped spark plugs, etc. A TINY movement of that mixture screw makes a BIG difference and you must remove the allen key and plug the hole and wait a moment for things to settle before reading the meter. Never try to adjust the mixture to compensate for other problems. In fact, touching that mixture screw is the LAST thing you do. It probably was just right and is not your problem and is better off left alone. Now that you have messed with it you have no choice. Go over all of the previous work to make sure everything is perfect, all of the parts are good and no vacuum leaks. Check the timing and air filter. Make sure all of the systems, idle speed, vacuum and mechanical advance, are working correctly. When you are satisfied everything is good THEN you can try to adjust the mixture screw. To rough it in you crack it till an injector starts to open, and then go on from there. If you are way off you won't hear the frequency valve buzz. Till the motor warms up and gets into "Closed Loop" the meter should have a steady reading. Your best reference is the Workshop Manual.

[dean2526]

Gotcha! The mixture is fixed at 14.7 AFR. The purpose of the adjustment screw isn't to change that, it's to center the lambda system within its minimum and maximum control range.

As long as your meter is swinging back and forth, and you don't hear the frequency valve cutting in and out as it reaches the min or max of its control range, you're in a good spot, as far as that goes.

OK, wish me luck tomorrow, ha!

[dean2526]

Before you even think of touching that mixture screw you must make sure EVERYTHING is PERFECT! No vacuum leaks, good O2 sensor, all of the injectors opening and closing properly and good spray patterns, clean and gapped spark plugs, etc. A TINY movement of that mixture screw makes a BIG difference and you must remove the allen key and plug the hole and wait a moment for things to settle before reading the meter. Never try to adjust the mixture to compensate for other problems. In fact, touching that mixture screw is the LAST thing you do. It probably was just right and is not your problem and is better off left alone. Now that you have messed with it you have no choice. Go over all of the previous work to make sure everything is perfect, all of the parts are good and no vacuum leaks. Check the timing and air filter. Make sure all of the systems, idle speed, vacuum and mechanical advance, are working correctly. When you are satisfied everything is good THEN you can try to adjust the mixture screw. To rough it in you crack it till an injector starts to open, and then go on from there. If you are way off you won't hear the frequency valve buzz. Till the motor warms up and gets into "Closed Loop" the meter should have a steady reading. Your best reference is the Workshop Manual.


So unless anything has happened to the car since May (less than 1,000 miles), all of those things were fine as DMC revamped the whole car (except for the missing CO2 plug which I think came out when I replaced the stock air intake with the cold air intake kit). The issue I was having was when the car was cold it was REALLY sluggish, like to the point where I had to wait until there were no cars coming before I would pull out into the road. Once the car warmed up, it was great. So DMC said to adjust the mixture very slightly, but then I found the Actron dwell videos and figured that was a more accurate way to do it. Once I went down that rabbit hole, I made so many adjustments I have no idea where the screw was when I started. I am thinking it's way too rich at this point, so I will dial it back counterclockwise and hope that it wont stall so I can hook up the Actron and get a reading. Thanks.

[bytes311]

My car used to feel sluggish on cold starts. I had to let it warm up before driving or it had no power. Ran perfect otherwise. That turned out to be a warm-up regulator aka CPR that was out of spec and needed to be re-calibrated.

There's a vacuum diagram on the underside of the engine cover, make sure everything matches it.

[dean2526]

My car used to feel sluggish on cold starts. I had to let it warm up before driving or it had no power. Ran perfect otherwise. That turned out to be a warm-up regulator aka CPR that was out of spec and needed to be re-calibrated.

There's a vacuum diagram on the underside of the engine cover, make sure everything matches it.

They rebuilt the warm up regulator, so it's essentially new. How do I calibrate it?

[bytes311]

They rebuilt the warm up regulator, so it's essentially new. How do I calibrate it?

I had a shop do it. :)

[dean2526]

I had a shop do it. :)

Cheater!

[Bitsyncmaster]

[QUOTE=dean2526;284111]Cheater![/QUOTE

There is an adjustment for cold pressure on top of the WUR. You can insert a screw in it with some spacer to pull it up. You need to press it down if you need to move the cold pressure the other way. So it just moves up and down and stays put with friction. The hot pressure adjustment is under the bottom cover. It is an Allen wrench adjustment. I drilled a hole in the bottom cover after I removed the cover. With our WUR you need to plug that hole when your done adjusting.

[dean2526]

[QUOTE=dean2526;284111]Cheater![/QUOTE

There is an adjustment for cold pressure on top of the WUR. You can insert a screw in it with some spacer to pull it up. You need to press it down if you need to move the cold pressure the other way. So it just moves up and down and stays put with friction. The hot pressure adjustment is under the bottom cover. It is an Allen wrench adjustment. I drilled a hole in the bottom cover after I removed the cover. With our WUR you need to plug that hole when your done adjusting.

So what do you think I should do if it's running sluggish on cold, should I press the screw down or up?

[dean2526]

It was way too lean. I had to turn clockwise almost a half a turn. Now it's running dead between 15-20 on the dwell. Hopefully that will do the trick. Will try tomorrow on cold. Thanks for the help everyone.

[Jonathan]

...the missing CO2 plug

Did you use something else to plug that hole in the meantime? That's a potential vacuum leak if it's not plugged.

[dean2526]

Did you use something else to plug that hole in the meantime? That's a potential vacuum leak if it's not plugged.

Yes, I got a new plug.

[David T]

Just because you had a shop work on the car you cannot assume everything is as it should be. Obviously it wasn't because you had a problem which is now compounded by your attempting to "fix" it by adjusting the mixture screw. That adjustment affects the whole range of fuel flow. Other systems can modify certain ranges of fuel flow to compensate for cold starts, idle, sudden acceleration, etc. The way to correct the problems you now have is to start from the beginning and go over each system and verify it is working properly. I would start with a compression test and "read" and regap the spark plugs. You may also need a valve adjustment. Essentially what you now have to do is a full and complete tune-up not taking any previous work for granted.

[glockworks21]

2 cents

Maybe i missed it, maybe someone can correct me. I remember having a bad 02 sensor and the car barely swung (on a digital gage)
It was a bad one out of box. I went through 2 or 3 sensors before it started swinging again (the 10 or so points). If its only swinging a couple points could it be a bad 02?

[Bitsyncmaster]

2 cents

Maybe i missed it, maybe someone can correct me. I remember having a bad 02 sensor and the car barely swung (on a digital gage)
It was a bad one out of box. I went through 2 or 3 sensors before it started swinging again (the 10 or so points). If its only swinging a couple points could it be a bad 02?

My lambda ECU will not swing as wildly as the stock ECU. Don't go by the amount of swing. Do a small adjustment and the reading should change.

[dean2526]

Just because you had a shop work on the car you cannot assume everything is as it should be. Obviously it wasn't because you had a problem which is now compounded by your attempting to "fix" it by adjusting the mixture screw. That adjustment affects the whole range of fuel flow. Other systems can modify certain ranges of fuel flow to compensate for cold starts, idle, sudden acceleration, etc. The way to correct the problems you now have is to start from the beginning and go over each system and verify it is working properly. I would start with a compression test and "read" and regap the spark plugs. You may also need a valve adjustment. Essentially what you now have to do is a full and complete tune-up not taking any previous work for granted.

It was DMC Orlando, not just a regular shop. Before I bought the car, they took the car in and went over every aspect of the car before selling it to me (replaced multiple parts and gave me a warranty), so the mixture is the only issue. It might be the warm up regulator, which they have offered to rebuild (again), which I may take them up on. DMC Orlando has been great, if I were closer to them I would have just brought the car in. If it were not just a cold start issue (which resolves in 5 minutes after start), I would be more concerned.

[dean2526]

2 cents

Maybe i missed it, maybe someone can correct me. I remember having a bad 02 sensor and the car barely swung (on a digital gage)
It was a bad one out of box. I went through 2 or 3 sensors before it started swinging again (the 10 or so points). If its only swinging a couple points could it be a bad 02?

Did the bad O2 sensor result in poor performance all around or just cold starts? I am only having issues with cold starts, once warm the car runs great.

[dean2526]

My lambda ECU will not swing as wildly as the stock ECU. Don't go by the amount of swing. Do a small adjustment and the reading should change.

Yes, I noticed small adjustments are the key, too much turning either way makes huge changes. When I redid it last night, I turned on the A/C and lights to put max load to see how it changed and then did the adjustment. I'm in FL so I always have the A/C on.

[David T]

Every shop is only as good as it's worst mechanic on a bad day. Everyone makes mistakes and DMC Orlando is not immune. In fact there are a couple of stories about work done there that do not put them in the best light. That is not to say every job they do is not top notch but they have made mistakes. Shooting off the parts cannon will eventually get you going but it is the most time consuming and expensive way to fix a problem. Taking the time to do some diagnosis will avoid replacing a lot of good parts.