OK, hope this is the right forum for this....

I've been chasing an apparently random miss on my 383 SuperRam setup, and been DIY prom-ing as well. Can't seem to get it consistent so did some more trouble shooting and here's some of the details of things I've found.

Initial driving in the morning (cooler temps) is the best. And that's while in closed loop.

Turning on the A/C with the fan on high when temps are high (95-100 here in Dallas) is guaranteed to cause it to almost stall at idle, and causes the miss to occur very noticeably.

While datalogging with Datamaster, I noticed that the battery voltage is usually only showing 13.5 or so volts, and when the A/C is turned on that drops to about 13 or possibly a little bit less.

Thinking this was too low, I went by a shop and they hooked up their meter to the battery while the car was running to try and check the alternator output.

The interesting thing here was they were showing 13.8-14.0 volts even with the A/C turned on as well as the headlights and radio. But Datamaster was reporting that the ECM was seeing right at 1.0 volt less than they were reading on their meter (12.8-13.0v).

I know the ECM varies the pulse width based on the voltage it's seeing, so I'm wondering if this is a source of my miss.

Suggestions, ideas, fixes?


- Vern

 

Were they reading the voltage as it was coming off the battery while the engine was running?

 

Yep, they were hooked up to the two battery posts.