[mjeffries]

2003 Nissan SE-R

Car has been running just fine; usually idles around 14.7. No complaints there!

A few days ago it started to idle extremely lean. My wideband only reads up to 18.0 and I was going beyond that, wideband would just read "---". Its not a problem with the wideband. Sometimes I'll notice a shudder or studder from the car when idling and the RPMs may drop for a second or so, so theres definitely a problem.

A/F ratios under cruise conditions are just fine.

A/F ratios under load, while I haven't done much of it, seem to be a little leaner than they used to be.


I cleaned my MAF and air filter today, didn't help one bit. I do have a piggyback fuel controller but that isn't going to help since the car runs in closed loop during idle.

Any ideas?

[grandprixgtp_91]

Well as long as its going into closed loop for sure then there is no reason for it to be that lean the computer should pick up on that and fix it, so its possible that maybe your o2 heater is bad or just a defective o2 sensor. if your o2 heater is bad and the o2 sensor is far enough away from the engine it wont go into closed loop, maybe while cruising from the heat but not at idle.

If this is the case then that would indicate a poor ecm tune, basically the computer is tuned to run lean and the ecm tries to compensate for it under closed loop operation so if it does turn out to be the o2 sensor you might want to get the ecm tuning taken care of.

thats just a guess, you could try changing your plugs, and giving it an all around tune up too though.

Jake

[Robert]

Originally Posted by mjeffries

2003 Nissan SE-R

Car has been running just fine; usually idles around 14.7. No complaints there!

A few days ago it started to idle extremely lean. My wideband only reads up to 18.0 and I was going beyond that, wideband would just read "---". Its not a problem with the wideband. Sometimes I'll notice a shudder or studder from the car when idling and the RPMs may drop for a second or so, so theres definitely a problem.

A/F ratios under cruise conditions are just fine.

A/F ratios under load, while I haven't done much of it, seem to be a little leaner than they used to be.


I cleaned my MAF and air filter today, didn't help one bit. I do have a piggyback fuel controller but that isn't going to help since the car runs in closed loop during idle.

Any ideas?

Have you checked your plugs lately? If one of them is fowling causing that cylinder to run rich the car will over advance timing to compensate for it causing you to run lean.

[mjeffries]

There was a vacuum leak at the PCV thingamajigger; an O-ring was missing. That corrected the issue with running lean at idle. A few days later a new issue popped up.

Idle and cruise are fine but under WOT the car runs lean. Previously the Turbonetics reflash would have my A/F ratios in the 10s under WOT, I had to subtract up to 20% in some cases with my piggyback fuel controller just to get in the 11.5-12.0 range. Now under WOT with no corrections on the piggyback fuel controller (in other words, only running off of the Turbonetics reflash AND my water/meth injection) I am running lean. Two to three full points higher than what I used to see.

I changed my plugs today and that helped out a lot. Now on the reflash + water/meth injection my A/F ratios are in the 11.5-12.0 range. There is still a problem though, as I used to subtract up to 20% of the fuel to achieve those A/F ratios. I still have a weak link somewhere. A buddy of mine is going to help me test my fuel pressure next week. In the meantime, anyone want to help me read my old plugs? Two shots of each plug starting with the one closest to the drivers side.












They were all gapped at .033.

[zeniac]

My Spec V idles at 17++. Very lean.
It's been that way since I installed the turbo kits.

http://ehomey.com/Video%20Gallery/Ca...ges/WarmUp.mpg

No problem for 1.5 years.

[zeniac]

i believe i have solved this extremely lean condition at idle. for some reason the ecu was in "open loop" at idle (even after warm up), which is incorrect. in general, "open loop" - ecu ignores heated O2 sensor input in determining air/fuel mixture. "closed loop" - ecu uses heated O2 sensor input to determine correct air/fuel mixture.

above 3000 rpm, ecu defaults to "open loop."
under 3000 rpm, ecu uses sensor and driver's inputs to determine "open loop" or "closed loop."

when my car was idling in "open loop", AFR was extremely lean.
i replaced crankshaft and cam position sensors (69$ at dealership) because the ECU registered a P0335 SES (bad crankshaft sensor). double check my vacuum hoses, and tightening some bolts.
now it idles in "closed loop." AFR is in 14.x and 15.x at idle. i am pleased.

you have to make sure your car idles in "closed loop."

[mjeffries]

Thank you for the input. Currently the vehicle is idling perfectly (14-15) about 90% of the time. The other 10% my wideband will drop below 18.0 (the lowest it reads) and the car will studder a little bit.

The only code I'm currently dealing with is P0172 (System too rich Bank 1)

Fuel sys 1: CL
fuel sys 2: CL-Fault
Calc Load %: 34.51
ECT (F): 186
STFT B1 (%): -1.56
LTFT B1 (%): -27.34
Eng RPM: 2462
Veh Speed (mph): 62


It says too rich but I didn't notice anything unusual on the wideband.

I'm starting to think this car has a few too many demons to track down.

[Robert]

Originally Posted by mjeffries

Thank you for the input. Currently the vehicle is idling perfectly (14-15) about 90% of the time. The other 10% my wideband will drop below 18.0 (the lowest it reads) and the car will studder a little bit.

The only code I'm currently dealing with is P0172 (System too rich Bank 1)

Fuel sys 1: CL
fuel sys 2: CL-Fault
Calc Load %: 34.51
ECT (F): 186
STFT B1 (%): -1.56
LTFT B1 (%): -27.34
Eng RPM: 2462
Veh Speed (mph): 62


It says too rich but I didn't notice anything unusual on the wideband.

I'm starting to think this car has a few too many demons to track down.

Its likely registering this because its detecting abnormal behavior when it adjusts the long term and short term fuel trims. You can certainly continue hunting but I long ago stopped worrying about any Sentra I owned not throwing a code. Sure for the most part the kit will leave you codeless and with more power but as you add more parts and tune the car more or add other things they will throw codes. A small piece of black electrical tape fixed my SES light and I just ran a Palm powered OBD2 scanner in the car with me to laugh at the codes I threw in my track car.

[mjeffries]

I'm not so much worried about a code like the one above as I am the problems that only show themselves every now and then. For instance, the car will run great for a few days. Then for a few days it will go extremely lean at WOT. Then it'll go back to acceptable A/F ratios at WOT for a few days and the cycle begins again. I'm having one hell of a time finding that one.

I'm trying to talk myself into parting out the car and buying a 350Z. Its just so hard to do when I think about all of the money I've wasted in this grocery getter.

[Robert]

Originally Posted by mjeffries

I'm not so much worried about a code like the one above as I am the problems that only show themselves every now and then. For instance, the car will run great for a few days. Then for a few days it will go extremely lean at WOT. Then it'll go back to acceptable A/F ratios at WOT for a few days and the cycle begins again. I'm having one hell of a time finding that one.

I'm trying to talk myself into parting out the car and buying a 350Z. Its just so hard to do when I think about all of the money I've wasted in this grocery getter.

You may want to check the same sensors that zeniac did if you haven't already. The Spec V is a great car. Hell I owned one before my 350Z and i have to admit that despite all the fun I have had in my 350Z I still miss my Spec V. It was far and away my most favorite car of the one's I've owned. And I wasn't even boosted in the Spec. .