Hey guys, new to the forum and fords all together. I picked up a 97 about a month ago, traded my jeep for it. P.o couldn't get it to emissions test. The truck is a 4.6, flareside 4x4. It has Gibson headers and true duals. It also only has 1 cat per side. It has a cold air intake as well. I recently replaced a 02 b1s1 for a slow response cel.

Here's the problem, my truck idles rough, smokes a bit once in awhile and hesitates sometimes. I did a lot of reading on here about it, I've checked all vacuum lines, it has new plugs and wires, clean air filter...etc. So I got a new scanner that does live data...which I know nothing about.... My question is, it says my front 02s are between .400-.800...whatever that means lol and my rear 02s are reading nothing...but no cel. ...is this correct? Thanks, sorry for the long post.

 

It seems odd that your rear O2 sensors aren't setting the check engine light. However post-catalytic oxygen sensors are only for emissions purposes and do not effect engine performance. .4-.8 is a pretty good reading for the front O2 sensors so that should not be the issue.

 

Well, I found a bad crack in the PVC hose today, also changed the fuel filter, the p.o said he had done it but it was plugged solid. I haven't driven it yet but I hope that fixes things. Still am really curious about the rear 02s not showing any live data on the scanner

 

Rear oxygen sensor are not switching sensors to begin with. Only front oxygen sensors switch.

 

Rear oxygen sensors work exactly like front ones. If a catalytic converter is working properly the signal they give will switch much slower and much less but they both work the same.

 

OK thanks guys, guess I have some reading to do on the whole live data thing, it seems like an invaluable tool. However, replacing the fuel filter and fixing that PVC line restored all the power, idles great, no more smoke...tach is working correctly Now, wasn't before and I thought I had a header leak on the driverside which is now also gone...awesome. Now I can start modding it...

 

If that was the case the sensors would be the same for pre cat and aftercat. They do not fuction nearly the same as the front oxygen sensors. These trucks use a 1v oxygen sensor precat. The rear oxygen sensors are operating at specific voltage. The pcm has a specified range before the PCM will trigger a CEL for a cat efficiency code.

 

Live data is a great tool if you know what your looking for. There are certain pids that are useless when trying to diagnose a certain issue.

 

You're right, sorry. I didn't mean to say that both front and rear HO2Ss are the same. However they both work by sending a "switching" signal to the computer. As the exhaust mixture switches from rich to lean, the sensor switches voltage based on the amount of oxygen in the exhaust.