Lean Conditions-Long and Technical

[Pacman]

Story-I put my car on the smog machine at school to complete some labs and saw that the numbers showed VERY lean conditions. My emissions are off the charts. My NOx (200ppm-idle, 1150ppm-2500 RPM), HC's are very high, CO2 is about 12.5% and A/F ratio is about 19.5:1-22.5:1. I went to data screening and saw that my short term fuel trim and long term fuel trims are near optimal for being a ODBI car. But, for them being near optimal, my O2 Sensor is not switching lean/rich like its suppose to.

I performed a fuel volume/pressure test and came up with good volume but low pressure. Pressure is about 29PSI regulated, from my understanding, its suppose to be at like 40PSI. I've done nothing to the fuel system except new lines and a 300ZX TT Filter.

-Now, does the Z filter have a different filtering element then the stock 240SX filter (like a tighter weave or different filtering element that could cause a restriction)?
-Is there any other fuel pump tests I can perform using a voltmeter? I don't have the gauges or vacuum pump access since I'm out of school for the holidays.

I just put this motor in since the other motor started burning oil (possibly from the lean conditions?). I don't want this motor going out as well. I commute about 650 miles a week and its my only car. I'm almost to the point of selling since its benn a headache for the last 2.5 years of owning it; just one thing after another.

[idlafie]

Pac,
Check the vacuum line that runs from the BPT valve to the EGR. It might be disconnected or cracked/melted due to long term exposure to underhood engine temperatures....it's a rubber line that gets brittle with age. If the vacuum line is good then check the EGR valve & IAV valve for carbon buildup. The purpose of the EGR valve is to pump hot exhaust gases back into the intake airflow to reduce NOX emissions. If your NOX is off the chart, then it's because your EGR system is not working as it should. You'll also have to check the sensors/valves/vacuum lines for the EGR system to make sure they are functioning as they should be. See your friendly FSM for testing procedures.

As for your fuel flow question, I thought the Fuel pressure regulator limited the fuel flow ratio to 34 lbs, (Possibly up to 40 under load...not sure on that though..haven't worked on a fuel system in a while much less look at a FSM).
As for your fuel filter element, most aftermarket one stocked at your local parts slinger, (Purolator, Fram, etc..), are all pretty crappy. Looks like a paper cardboard type element....crack one open & you'll understand.

Oh..almost forgot. Test your 02 sensor AND your Engine Coolant Temperature Sensor along with the wiring leading up to the ECU and ground. You should be getting a signal off it.
http://www.forparts.com/o-21.htm

One last thing, check the honeycomb in your catalytic converter. Make sure it's not melted, clogged, or cracked. That can also cause bad emissions results.

As for your burning oil, usually not due to a lean condition... could be from wear & tear to valves, piston rings, or running rich.

Anyhow, hope this helps...
ID

[BOROSUN]

34psi with vacuum
43psi no vacuum/under load
29 psi definetly have some restriction. check if the any lines are kinked first.

first, i was thinking partial misfire but co2 looks good 12%. but then again you said hc is high usually signs of misfire and o2 is high too. check ignition, timing, & plug gap...etc. it can be numbers of things also like injectors/vac leak but, i would check that first.

i was thinking the o2s propably saw too much o2 (maybe from a leak) the computer fuel trim tries to compensate and adds more fuel. you been driving like this for awhile and has learned on the lftrim.
also sounds like your o2s is retardly slow. did you do the propane check, i meant o2s test? you should do that before you throw it away.or if its really old just git a new one. haha

as for burning oil is usually worn piston rings. thats why i always heat up my car before i put any load on it. :p

damn its 5:30, ive been watching the venture brothers marathon. time to sleep.

btw your lucky you got to run it on the dyno at your school. i didnt get to do that.

[Pacman]

I thought I heard a *slight* vacuum leak from behind my head but those lines are in good condition. This motor is running real well and i don't want it to become like the last. The line from the BPT to the EGR is brand new, I had that happen to me before.

The coolant temp. sensor is pretty new. No codes there but worth a test since its easy. I had to make a repair on the harness for the O2 sensor (coax part) so a test there with the DMM should be done. I'm gonna try to get my friends fuel pump out of his wrecked S14 and put in mine if insurance hasn't gotten it already. I wanna see if the pump is the problem.

My lines are new as well with no kinks. Slight bends all the way through the system.

CO2 should be in the 14% range, 12% is low from what UTI is teaching. The O2 sensor is new with the engine swap so I doubt that its the O2 function.

They got the smog dyno in there. They won't let us use the HP/TQ dyno for our cars. :(

I'm gonna run some tests on it when I get some time. New job at Toyota is working me 6 days a week but I have nights off.

[BOROSUN]

i guess it vary between engines but 12% Co2 is usually signs of a efficient engine and 14% is more efficient, anything below 12% is a problem.

what did you use to check the vacuum?

my guts is telling me its probably that low fuel pressure problem. i guess its good that your tackle that first. And try changing to a oem 240sx filter. also cleaning the strainer.

neways, so there's no signs of misfire at all?

btw you know if you fix this lean condition problem , Nox will probably drop also.

[Pacman]

I'm gonna change the pump with a different one and get a new filter at the dealer. I'll keep the Z filter around though. Thanks guys.

[idlafie]

Pac,

Did you inspect your catalytic converter?? Hi NOx could be due to a blocked catalytic converter or restricted exhaust system.

What about the pipe that runs behind your KA engine block connecting the exhaust back to the EGR valve?? Carbon buildup in the pipe & the EGR valve could also cause your hi NOx readings.

Try 'em both.....can't hurt. Beats pulling the fuel pump!!

ID

[Pacman]

True, but I replaced the EGR gasket just before the last engine blew and the piping was all clear. There *can't* a restriction ine the exhaust, its a turbo version N1. The cat is in good condition, I checked it all before the swap. I'm almost positive that the pump isn't supplying enough fuel. That would explain the higher HC's. A pump isn't that hard. If I don't get to wasted tonight, I'll check it all tomorrow. :D