High NoX, misfiring badly after inspection.

DeanWinchester

Registered User
I went down to get my SC inspected today and it was running fine. Got it on the machine and it failed the inspection, super high NoX readings, over 1100 on both tests. So, I take the car home and about halfway there, I go to pass someone and it's stuttering like all hell and I hear pinging. I immediately backed off on it and started to take it easy. 3/4 of the way home, it's stuttering and pinging even with partial throttle, no boost at all.

Engine temps were fine all the way through the test and all the way home. Codes are:

126 - MAP/BARO sensor - I have had this since I bought the car, I just unplugged the damned thing.

181 and 189 - Adaptive fuel too lean both banks.

So, obviously I have a nice lean condition, but what can cause this? I am on my way out right now to check the fuel pressure. Please tell me that those chuckleheads didn't melt my ~~~~ing pistons when it was on the rollers.
 
plug the sensor back in and see if it gets better, my understanding is that uses atmospheric pressure to determine how high above sea level, which determines how much fuel is used.
 
plug the sensor back in and see if it gets better, my understanding is that uses atmospheric pressure to determine how high above sea level, which determines how much fuel is used.

I had it plugged in when I went to get the inspection, unplugged when it started acting up, the way I worded it wasn't clear.

Fuel pressure:

Pump on - 40PSI
Pump off - 37PSI
Engine run - 35PSI
Engine WOT - 28 PSI

Those numbers seem way too low for me. Clogged fuel filter or weakening pump maybe?
 
Fuel filter did nothing, but the old one was dirty, so job well done there. Fuel pressure readings are still the same.

Bad pump, bad regulator or leaking vacuum/boost refrence hose on regulator.

WOT pressure should be about 40 psi plus 1 psi for every pound of boost. So if you are making 12 pounds of boost you should be seeing 52 psi. I'd start with the regulator and refrence hose.

David
 
Bad pump, bad regulator or leaking vacuum/boost refrence hose on regulator.

WOT pressure should be about 40 psi plus 1 psi for every pound of boost. So if you are making 12 pounds of boost you should be seeing 52 psi. I'd start with the regulator and refrence hose.

David

I just started reading about that. Sounds like the vacuum hose fell off or wasn't put back on when the previous owner changed the engine. Fortunately I found the misfiring issue, while under the car looking for the FPR, I found a spark plug wire hanging. They were tugging on the wires trying to find one to attach the RPM sensor to, they probably pulled it off.
 
The fpr is behind to the right of the return plenum

Found it. There was no gas in the line, but when I sucked on it I could lightly taste gas fumes. It held vacuum against my tongue just fine, so I doubt there is anything wrong with it. My vacuum diagram on this car is showing completely different ports on the return plenum than what I have. I moved the FPR vac line to where the boost gauge is hooked up now and the boost gauge to where the FPR was hooked up. Boost gauge still works, but I haven't checked the fuel pressure under load yet.
 
Found it. There was no gas in the line, but when I sucked on it I could lightly taste gas fumes. It held vacuum against my tongue just fine, so I doubt there is anything wrong with it. My vacuum diagram on this car is showing completely different ports on the return plenum than what I have. I moved the FPR vac line to where the boost gauge is hooked up now and the boost gauge to where the FPR was hooked up. Boost gauge still works, but I haven't checked the fuel pressure under load yet.

Lines for the FPR and the boost gauge should be hooked up to the return plenum (after supercharger), so they get vacuum and boost signals. If hooked to the inlet plenum side (before supercharger) you will only get a vacuum signal .

David
 
Lines for the FPR and the boost gauge should be hooked up to the return plenum (after supercharger), so they get vacuum and boost signals. If hooked to the inlet plenum side (before supercharger) you will only get a vacuum signal .

David

Yeah, I get that. I fixed the BARO sensor and it seems to be running fine now. Only thing is that the check engine will flash if I get into boost. No doubt showing lean. I will hook up my pressure gauge again tomorrow, check what is going on. Also have a few exhaust leaks I need to seal up, which can cause the high NoX.
 
I believe a flashing CEL is caused by a misfire. If you had a plug wire unhooked it is possible that the plug itself is fouled with unburnt fuel. A lean mixture will cause your high NOX readings.
 
If you still have problems with high nox. Pull the spout connector and put 3oz of pure acetone to 10gallons of gas. Then get it tested. My 5.0 went from 1000ppm to 250ppm after adding the acetone and pulling the spout.

Nox is also affected by the egr system.
 
Also pulling the spout plug will decrease the Nox. One of the local guys here did that to finally pass.

Thats what i had to do plus I also ran a can of seafoam though the intake system and fuel system. Numbers went from 14XX to 4XX Ca has the worst emission laws around:mad:
 
I believe a flashing CEL is caused by a misfire. If you had a plug wire unhooked it is possible that the plug itself is fouled with unburnt fuel. A lean mixture will cause your high NOX readings.

This is more of a stay on for 20 seconds, then go off. My old F150 would rapidly flash and it was a misfire. Where exactly is the spout plug on this car? Can't seem to find it.
 
Got the fuel pressure readings, the FPR is functioning properly now, jumps to 42PSI with a quick blip of the throttle. I have exhaust leaks, which is likely the reason for the high NoX as well as the lean codes. Oh and I found the SPOUT connector, it's right by the DIS. Going to get this crap fixed and retest.
 
If your vehicle is an early model it should be near the DIS module. It has two wires that terminate at a connector with a dummy plug in it.

Edit: To slow!
 
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Well, I found the source of my exhaust leaks. Couple of the rear manifold bolts backed out. Got those tightened back up and was still getting the lean code. Went through and checked for vacuum leaks, which I couldn't find, but I decided to go ahead and reseal the inter cooler/return pipes since I hadn't done it yet.

Holy crap what a difference, went from 11PSI of boost to nearly 14PSI and pulled hard all the way to 5K RPM, where before it felt out of gas by 4200. It was quick before, but it's downright nasty now, barking and spinning 2nd gear. Check engine light came on once during deceleration, then went out and didn't come back on, so we will see. I don't think that it's actually leaning out since I run cool and I get no pinging at WOT. I am sure that my injectors are maxed out though with the mods on it.

Going to go get a retest tomorrow.
 
After fixing those things you should disconnect the battery for 5 minutes so the computer will clear it's learned settings. Since these setting were learned with issues, it's better to clear them and let it learn the new configuration.
 
The spout plug is over on the passenger side of the firewall where the EEC test plug is and can be hard to find in the tangle of wires and connectors. If you look at the small connector with a plug in it on top of the A/C compressor it looks just like that.
 
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