Failing CA smog over and over. Running lean?

[Raven Tooth]

Long story short:

Just moved to California and needed to get my car to pass smog. Took the first test. Failed.

Replaced the cat, got an oil change and put in 91 octane. Failed by more. (my numbers were like 3000, gross polluter status)

Called my mechanic. The only numbers that were high were the Nitric Oxide, which he said indicated a lean running car. Suggested I replace the o2 sensor (which I should have done with the cat), so I did and failed again by about the same amount as the first time.

My car does seem to have a little hesitation off of idle when you go on the gas, but my car is certainly not running like crap. What could cause my car to run so lean? Bad MAF meter?

I sprayed down the main electrical connection with electrical cleaner spray and put some electric grease on it on the suggestion of the smog tech (said it can get corrosion on it which can effect the sensors. Didn't really seem to do anything when i started up my car this morning, but I only let it run for 5 minutes and it was kind of cool outside. Thoughts before I take it in?

[KenC]

make sure you run the engine for a while before going in. why does your car have a hesitation?

[jlevie]

High NOx is either a lean running engine or bad catalytic converters. Since you've replaced those w/o any improvement you now need to address the possibility that the engine is running lean. The first step in that would be to have a smoke test run on the intake to check for leaks and to run the fuel system tests to make sure that the fuel system is working correctly. After those areas have been addressed there are plently of other possibilities. but it makes no sense to look into those until intake leaks and fuel system problem have been ruled out.

[Raven Tooth]

My injectors are brand new. I will look into having the car checked for air leaks and do a fuel system test. What would the fuel system test check, i.e. what could be wrong besides injectors?

[e30trooper]

You needa new cat. Run the car hard for like 15 mins b4 going to smog , dont turn it off till hes ready to test. Run some 91 oct. gas. And make sure you dont have any vacuum leaks. You should be grand after that.

[Raven Tooth]

I just put in a new cat and failed again. The car was warmed up and running 91 octane when tested. Think I gotta check for vacuum leaks.

[e30trooper]

thats weird. yea check vacuum lines. How do the car run? Idle funky? loss of power?

[Raven Tooth]

The car was running horrible when I first got it, it was super rich because of a blocked fuel return line. Once I fixed that it was a lot better. So I guess it was such an improvement that I don't really know what it should run like if it was perfect. Idle is sometimes a little funny when you start it up, but only kind of up and down a couple hundred rpm. And sometimes there's a little hesitation off of idle... like you press the gas and it doesn't respond much for the first 10% of the throttle. I think it's got to be related to that. I thought it seemed to run pretty good once it was warmed up but obviously something is wrong if I'm getting crazy high gross polluter numbers of NOx. It took the test obviously after it had warmed up.

[e30trooper]

check the AFM, could be bad. you can find them cheap.

[MonkeyMadness]

Did you unplug the battery? and reset the ecu after replacing the cat and O2 censer?

[Raven Tooth]

I had the battery disconnected when I replaced the O2 sensor. Is that all that's needed to reset the ECU?

[gw ix]

Do you have a MIL? Do a stomp test and get the codes.

Oh by the way what car is this?

[Raven Tooth]

The car is a 1989 325i.

Don't have a check engine light or anything. Didn't know what a stomp test until I just looked it up. I brought the car into the shop today though because I needed to get this figured out fast. I'll let you know what he says.

[Raven Tooth]

Mechanic says there were no major leaks, he replaced a couple small cracked hoses but they weren't horrible. The main thing he found was a bad coolant temp sensor. He said changing this has made the car run a lot better. He is also going to do a valve adjustment since my car is pretty loud with ticking valves. So hopefully I can pass Smog with these adjustments. I will let ya'll know how it goes.

[Raven Tooth]

Just wanted to update this thread to let you know I passed with flying colors after the work mentioned above. I think it was mostly the coolant sensor. My car also runs way better and doesn't have the throttle hesitation it had before off of idle.