[dale]

For EFI engines, what are symptoms that the O2 sensors are NOT working. When my engine is cold, no issues. When warm it "bucks" at low RPM, under low-load conditions. Does this sound like an A/F issue?

I've got bungs in 1 and 5, and also in the collectors; location of the sensors makes no difference to symptom.

 

[d42davis]

Did you check codes?

 

[dale]

Ignition system is apart right now.Will run codes when back together. Just wondering if malfunctioning sensors could result in symptom.

 

[snakelake]

I would check to see if they are wired right, left for left, right for right. Also what mods have you done to your engine, mine has lightly mods and I had a chip put in to help with the same problems that you described. Also check your voltage on your TPS at key on engine off

 

[tirod]

O2 sensors basically send a signal that the ratio is either low or high. After the element warms up, it transitions from one to the other according to the fuel/air ratio. When they "go bad," it's because they don't change rapidly enough - literally worn out at the molecular level. Bosch claims they should only last 80,000 miles.

Diagnosing them requires getting them to operating temps, which is why so many now have heater elements to speed things up for the EPA cycle. Secondly, they have to have input voltage to put out a signal, and third, they need to switch states rapidly enough that the computer doesn't flag them for slow response.

This is why more pro touring and competition cars have a running display of the EFI program on the dashboard to modify and diagnose things. It's really just one big multipurpose gauge displaying all the inputs.

 

[dale]

Thanks for the input. Will address when I get the ##@@* distributor back in. Having issues with the oil pump shaft.

 

[Wayne Presley]

The bucking is due to the tune, too much timing at lower rpms.

 

[tirod]

Oh, yeah, O2 symptoms - generally, as they age, they slow down, and the system goes rich, taking about 2mpg off the top. Don't know why it goes rich, I suspect that's better than lean and holing a piston.