Hello. I have a Ram that I replaced the heads and headgaskets. Bought broken down. It failed emissions because of high hydrocarbons and carbon monoxide here in Chandler, AZ. Sniffer test on roller. Only indication aside from failed test is smell from tailpipe. Trucks runs beautifully. Cranks 1 or 2 times and boom. Its on. Average compression PSI was 143. Vacuum gauge tells me vacuum is good. 17 at idle 19-20 when I rev and hold engine. O2 sensor, MAP, IAT, ECT all good. New plenum gasket, plugs and wires. cap and rotor. No smoke whatsoever. I am wondering if I am chasing my tail with this smell I have or is that normal for a obd1 5.9 V8. Would the emissions this truck produces ever pass a test now in 2021 in AZ. Don't know how they standardized test. They comparing my emissions to 2021 vehicles. If so I am never going to pass. Or is it actually running slight rich? If it was running rich this obd1 system is supposed to set a code but then again it is obd1. But O2 sensor was varying between .1 and .9. Truck is now emissions excempt because historic vehicle but would still try to fix if there is fixing to do. Only has about 500 miles on new heads and plugs I removed and were not black. Any advice? Am I chasing my tail or what may be wrong. Or is this normal. I replaced fuel pump assembly because I suspected fuel regulator but still the same. I am starting to suspect fuel injectors having too much flow but now I am going into speculation and they don't seem to be leaking. Don't want to be parts changing alot. Any advice/ suggestions/ input? Thank you

 

Keep in mind the PCM controls the amount of fuel via pulse width based on the O2 sensors so it can (within limits) adjust to higher or lower flow injectors. The O2 sensor switching voltages sounds right. You should have two, do they both behave the same ? Ideally look at it with a scan tool but they are far and between for OBD1 vehicles.

The test failure could well be due to a catalytic converter beyond its life span. In that case there is nothing wrong with the fuel injection system and OBD1 doesn't monitor catalyst efficiency.

 

Well I back probed the O2 sensor since I don't think or haven't seen a scanner with obd1 live data. Multimeter was varying the voltage like I stated so O2 sensor is good. Perhaps that signal isn't reaching the ECU. Might backprobe that O2 signal at ECU. Only has the precat O2 sensor since the ECU doesn't monitor the cat. Cat is brand new. Has a high flow cat from flowmaster. Just wondering if I am chasing my tail since the truck drives beatifully and engine seems healthy. Perhaps a smell coming out tailpipes is normal since it is a 5.9 V8. I have been around old carbed V8s and that is what it smells like to a lesser degree

 

How old is the O2 sensor? Just because it appears to be working, doesn't necessarily imply that it is.....

 

Brand new by NTK. Also replaced the ECT with new one since they overheated engine. MAP and IATwere on there but tested out fine. I am gonna remove and clean throttle body with IAC valve. Maybe insufficient airflow at idle.

 

Thanks for your help guys. I messed up and crossed the #6 and #8 wires 😑 the wires I got were not numbered and I can see my 6 and 8 on the masking tape rubbing of or something. Honest mistake but atleast I fixed it myself and I learned ALOT in the process