jonrdory

I did blow out that tube. MAP sensor check out too.

NOX failure Colorado emissions. The balance of the gases pass with substantial margin. I have numbers and graphs… Fuel trims and O2 sensors appear to be working fine per the report numbers. Nothing high or way off. Long term trim on both banks read 0.001 for every speed STFT O2S, both banks, S2 show 99.2%... I believe that means the CAT is working Here are the steps I’ve performed: Replaced elbow to upper plenum, it was cracked and hardened… 2nd check, NOX higher… Replaced small rubber tube that connects the EGR valve to the EGR-BP valve, it was completely failed. 3rd check, slightly lower NOX but still fails Removed EGR solenoid, bench tested. Clicks and is tight Removed EGR-BP valve. Provided positive pressure to lower port, valve opens remove pressure valve closes- Appears to work fine. Replaced all vacuum lines from EGR solenoid to EGR-BP valve and to EGR valve. Applied vacuum to EGR at idle, car runs rough and dies as expected… Replaced power brake boost tube… cracked Pulled and inspected MAF. Clean as a whistle Pulled and inspected EGR valve, clean, no build-up, but blew out every port Did not pull EGR tube down to exhaust manifold… maybe I should inspect this, low probability…. Installed a vacuum gage between the EGR solenoid and the EGR-BT valve and drove the car. Needle showed vacuum as I accelerated but dropped as I eased the throttle, repeats as I accelerate and ease (shows vacuum then drops). At steady 55mph there is no vacuum going to the EGR-BP valve. I read in a separate blog that one person found that as the solenoid heated the resistance bumped to about 5k indicating a bad coil. I tested this solenoid valve cold at 36ohms, then at 42ohms with the valve at 137F (laser thermometer)…. not heat related…. So, this is where I’m stuck. Does the ECM hold the EGR solenoid valve open, then the EGR-BP valve switches vacuum based on exhaust pressure? IF this is true, then something is wrong between the ECM and the EGR solenoid… Am I on the right track? Any other suggestions? Pathfinder has 247k miles, no leaks, runs great, wife owed it new and handed down to daughter who loves it and wants it fixed!… J help