Stock ECU is running too lean? - Fuelly Forums

Android Users - Coming Soon! - Migrating from aCar 4.8 to 5.0

Reply
 
Thread Tools Display Modes
 
Old 09-30-2010, 08:49 AM   #1
Registered Member
 
Join Date: May 2010
Posts: 5
Country: United States
Stock ECU is running too lean?

I'm running the stock ECU on my OBDI Nissan SR20DET (s13 red top) motor and everything has been fine for about 15,000 miles. I've always used the same Wideband (PLX) sensor, sending a narrow-band signal to the ECU. Lately under slight load the A/F starts creeping lean. At around 50-80% throttle the A/F will creep up to 16, maybe even 17! I've even seen 20 before on a really hot day because the symptom seems more pronounced with higher ambient temps. However, at higher RPM's at WOT, everything corrects with A/F dropping into the 12's and 11's. What could be causing the lean problem?

Should I replace the 02 sensor? I'd like to run a 2nd sensor to test mine somehow. I've tried another MAFS but had the same symptoms. The fact that it operates properly at WOT elilminates a lot of things like clogged fuel components, bad FPR, etc. Any thoughts?
__________________

1969 Datsun 510 is offline   Reply With Quote
Old 10-01-2010, 04:39 AM   #2
Registered Member
 
Join Date: May 2010
Posts: 5
Country: United States
Re: Stock ECU is running too lean?

I noticed this morning that the lean condition seems to go away as soon as I reach WOT. I guess this is when the ECU switches from closed loop to open loop? So in closed loop the A/F is very lean, but once in open loop it is fine. Seems like a o2 sensor problem maybe? How long should a WB o2 sensor last?
__________________

1969 Datsun 510 is offline   Reply With Quote
Old 10-03-2010, 05:36 PM   #3
Member
 
Join Date: Sep 2009
Posts: 33
Country: United States
Location: New Jersey
Re: Stock ECU is running too lean?

In general...
The ECU will go into open loop mode with WOT and ignore the O2 sensor. If not too expensive I'd try replacing the O2 sensor.
You can also check the other inputs to the ECU like air temp sensor, engine temp sensor, etc.
N2UAD is offline   Reply With Quote
Old 10-04-2010, 06:32 AM   #4
Registered Member
 
kamesama980's Avatar
 
Join Date: Nov 2007
Posts: 742
Country: United States
Location: Columbus, IN, USA
Send a message via AIM to kamesama980 Send a message via Yahoo to kamesama980
Re: Stock ECU is running too lean?

how many miles on the engine/gaskets? if it's going through any oil, it could be damaging the sensor but that it's reading rich at WOT makes me wonder. maybe try calibrating it.
__________________
-Russell
1991 Toyota Pickup 22R-E 2.4 I4/5 speed
1990 Toyota Cressida 7M-GE 3.0 I6/5-speed manual
mechanic, carpenter, stagehand, rigger, and know-it-all smartass
"You don't get to judge me for how I fix what you break"
kamesama980 is offline   Reply With Quote
Old 10-05-2010, 05:56 AM   #5
Registered Member
 
Join Date: May 2010
Posts: 5
Country: United States
Re: Stock ECU is running too lean?

Not using any oil. It's lean at WOT, not rich. How would one calibrate a WB o2 sensor? Send it back to PLX?
1969 Datsun 510 is offline   Reply With Quote
Old 10-05-2010, 09:41 AM   #6
Site Team
 
Join Date: Dec 2006
Posts: 656
Country: United States
Re: Stock ECU is running too lean?

Please refresh me. Do you have a NB connected to the ECM and a separate WB O2 sensor?

-BC
__________________
Think you are saving gas? Prove it by starting a Gas Log, then conduct a proper experiment.
bobc455 is offline   Reply With Quote
Old 10-06-2010, 10:00 AM   #7
Registered Member
 
Join Date: May 2010
Posts: 5
Country: United States
Re: Stock ECU is running too lean?

No, I'm using a PLX (brand) SM-AFR (model) wideband controller and a Bosch 17014 5-wire WB O2 sensor. The controller has an analog output scaled to simulate the output of a narrow-band sensor. This output is connected to the stock ECU.
__________________

1969 Datsun 510 is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
CRX + D15Z1 Timing/CEL Question MakDiesel General Maintenance and Repair 1 03-20-2008 05:53 PM
60 mph - how do you do it? McPatrick General Fuel Topics 91 12-10-2007 10:18 PM
fuel 93dagsr Experiments, Modifications and DIY 5 11-29-2007 06:49 AM
Any Motorcycle MPG sites ? razmataz Motorcycles 15 07-29-2007 07:04 PM

Powered by vBadvanced CMPS v3.2.3


All times are GMT -8. The time now is 11:23 PM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.