Dwell meter results

[coreydmc]

Hi everyone, my car was running really rich. I bought a dwell meter years ago and never used it. Today I connected it and the reading was high around 30. I tried to set it between 15-20. The needle doesn't really swing it stays at 19. Is that a good thing or should the needle swing?
Thank you
Corey

[coreydmc]

I forgot to mention I am using a Actron dwell/tach/volts meter. I'm also using the 8cyl scale. The other day the needle was sweeping and now it's more steady. My car really isn't hunting when warmed up.

[Ron]

After all other setting have been made, the engine warmed up, and the access hole plugged, it should swing (+/-) across 20°.

[coreydmc]

Yes the other setting have been made. I also let the engine warm up and let the fans come on twice. If I adjust it closer to 25 or 30 the dwell meter will swing. When I make small adjustments at a time, each time putting the plug back it for a true reading, when I get between 15-20 the needle doesn't swing it stays more steady.
Thank you for your time
Corey

[Ethan Rode]

Hey Corey,

If your lambda probe (o2 sensor) is more than a few years old, replace it. The quality of data from the dwell meter method is directly effected by the quality of the sensor

[mark w]

what happens if you rev is up? to like 2000 rpm, and then hold it there?

[Michael]

No swing indicates there is no signal or correction in the o2 circuit. As mentioned, if the sensor is old, they are cheap and easy to replace. If the car has had little time to run at anything other than idle, the probe can get contaminated as idle does not generate enough heat to burn off.

Mixture is the absolute last thing to set but one of the first to check to zero in on issues. Problem is you can correct and compensate for a lot of unmetered air or fuel by adjusting the mixture. These engines can run very well with a LOT wrong with them so once all these band-aid previous owner fixes build up to major running issues, you pretty much have to start at the basics and work up.

Without knowing the history, I would just start with a new o2 sensor. If a new sensor doesn't correct the problem, it's back to checking fuel pressure, vacuum leaks, idle circuit and so on.

If/when you do replace the o2, set mixture in closed loop then take it put for a good drive. Get those RPM's up and stay out at least 5-10 minutes, then immediately check the mixture again. You might have to zero it in a bit once the probe has had a chance to function in the right temp range. You should be seeing roughly a 10° swing centered over the 20° mark.

PS: Get a GOOD O² sensor. I ran a side by side with a cheap Dgo sensor and a Bosch from DeLorean Performance. The difference between the two was obvious in both warm up time and voltage ranges.