Fuel/Air Mixture

[Toms240420]

I didnt really get anything from my search about my ?, or maybe i'm just to stupid to understand. anyway how can i adjust the Fuel mixture and what can i do to help "Running Rich"? thanks for any info.

[NISTECH]

mixture is not adjustable on an injected newer model nissan. you need to find what sensor is miss informing the ecm of the current condition. i.e. O2 sensor, MAF sensor, coolant temp sensor.

[Q45tech]

The ecu calculates the fuel injector open time from rpm, tps, maf voltage........easy because the displacement is known.It has preprogrammed look up tables for every possible operating condition which are compared to on the fly calculated values.

147 cuin/2=73.5 cuin per rev x RPM divided by 1728 times the volumetric efficiency [10-90%] [TPS - throttle position]= equals CFM which is corrected for density [+- 15%] by the MAF..... then the O2 sensor corrects the result to try to maintain a 14.7 AF at cruise.

....If any sensor is reading wrong by 20% weird things start to happen as the ecu may resort to fail safe to keep the engine running.

All the above assumes the coolant temp sensor is reading 176F and the engine is warm not overheated [above 194.9F starts the safety protocol].

A few tenths of a volt error in the MAF reading [1.20 idle, 1.70 cruise, 4.00+ volts WOT high rpm] can make a difference.

[NISTECH]

OUCH my brain hurts!!!

damn engineers :rant

J/K

[Toms240420]

i have just read these replies. Q45 lost me after "The ec....." great information though, i save it in my Special Car info file. maybe one of these days i will be able to decipher it. So check sensors, but how? could i find all the info in searches.

[NISTECH]

yes I have posted on several different threads on how to test these items but I believe there is a faq on the maf check. the o2 sensor is testable but requires a pretty expensive peice of equipment to check it accurately. Its called a dso(digital storage oscilloscope) i would say if its old replace it. it would be cheaper then the tool. I have one but I fix broken cars for a living and repair electronic housewares for amusement..lol .

[Toms240420]

I would love to be able to figure out and just fix **** all day, i myself dabble in "trying" to fix electronic houseware for amusement. anyway, i will search the threads, but roughly what should i pay for a O2 and could i do it myself with minimal tools.

[NISTECH]

7/8 wrench or if you have an autozone loan a o2 socket from them. price wise it varies but definitly less then the 2 grand for the dso. You can pick one up for less the 50 bucks at autozone. but if you get it there I recommend you get a boush. it is the equivalent to the factory one.

[Toms240420]

yeah 50 bucks opposed to 2 Grand. thanks man, i have already started to look in my book. i am going to change out a lot of stuff, just because i dont know how old everything is. just have to pick at it, i dont plan on getting rid of my baby for a very very long time. thanks again for your time NISTECH.

[Q45tech]

You can purchase cards that plug into a desktop computer for $150-$250..........that emulate oscilloscope functions and of course the old computer stores the data. And you can print hard copies! And post the graphs!Great use for an old Pentium II 350 MHZ machine.You can buy great little adapter that plug into parallel ports on lap tops also free software.

http://www.picotech.com/The best company, best prices most range of products even if in UKhttp://polly.phys.msu.su/~zeld/oscill.html

Check ebay:http://cgi.ebay.com/ws/eBayISA...=4677$105 is the bid!!!!!!!!!!!!!!!!!!!

There is no excuse for every human [car nuts like us] to not have an oscilloscope!