running a little lean..

[evolution23]

His engine goes lean when cold (when o2 sensor is initially not looked at for A/F ratio adjustments), then doesn't if left for a period of time in the sun. That makes me think it's the ECU coolant temp sensor giving incorrect readings or something inside cooling system got stuck on coolant temp sensor.

Exhaust leak can allow oxygen to enter exhaust which o2 (oxygen) sensor can pickup.

Try asking someone to block end of exhaust for a short period of time (when engine is idling) while you listen for exhaust leaks around dumppipe (also known as outlet pipe or down pipe), etc.

i did the thermostat and new coolant, i read about engines getting air locked after something like this, is that a possibility? my water temp gauge seems to be reading normal 180 - 200 Fahrenheit

as for the exhaust check ill give it a try early next week!

[Skym]

Doubt it, as engine probably would overheat.

There's 2x coolant temp sensors. One sensor for dash, the other sensor for ECU (both located on engine side, close to top radiator hose).

Faulty ECU coolant temp sensor would trigger coolant temp sensor error code on ECU.

[evolution23]

Doubt it, as engine probably would overheat.

There's 2x coolant temp sensors. One sensor for dash, the other sensor for ECU (both located on engine side, close to top radiator hose).

Faulty ECU coolant temp sensor would trigger coolant temp sensor error code on ECU.

hmm alright ill get out my trusty piece of wire and jump the pins and check for codes lol. by the sounds of it though its not a big deal and isnt harming my engine. so hopefully its not lol

[beacher1B0]

Check for loose valve covers.
During my yearly self inspection, i noticed my valve covers were loose. Definetly loose enough to cause a vacuum leak thru the pcv system. So i tightened em. Brought my idle back down to the 700s apposed to the high 700s low 800s rpms it was idling at. Also fatten up my AFRs at all ranges. Not much but a couple points. My RB20 runs alot better, not that it was running bad in the first place.

[evolution23]

bumping an old thread with some dreadful new info/pics.. need some help

[trunks_phil]

When I start my rb25 it goes from 15-16 and sometimes 17 for a bit then goes down to 14-15 when it's fully warmed iono if that's normal ?

[markdett]

To me this sounds like a coolant temp sensor issue. As the ECU uses the coolant temp sensor as a main input specially for cold starts, when these play up it can lead to all types of wierd symptoms.

These will not always log a fault code within the ECU. Since your running a STD ECU anychance you can get consult connected (or any other scanner which can monitor data) and check what your coolant temp sensor is reading?

You can also stick a variable resistor between the two terminals of the coolant temp sensor wiring, play around with the resistance and see if that changes your problem (or move the temp when viewing data).

Hope that kind of leads you in the correct direction!

[markdett]

When I start my rb25 it goes from 15-16 and sometimes 17 for a bit then goes down to 14-15 when it's fully warmed iono if that's normal ?

Your vehicle will run lean when its cold, to help get the engine up to operating temp.

When your coolant temp sensor is faulty, 9 times out of 10 it will cause the vehicle to run lean all the time, which usually only happens at idle.

[Skym]

Should run richer than 14-15 A/F ratio when cold, then leans out to 14-15 A/F ratio. If ECU coolant temp sensor is faulty it probably would select wrong part of tables (leaner parts). If have Nistune tuning software + Consult cable, can download maps, tables, etc and see what part of tables ECU is using in realtime.

[trunks_phil]

So is it richer or leaner when cold?

[speed]

wouldn't have this problem if its driven more korbin!! ahha

[evolution23]

I run slightly lean when cold/idle. When cold at idle aNd under load i see 15/16/17 (17 rarely) but see normal numbers under boost.

When warm (either been sitting in the blazing sun all day or been driving and all up to temp) numbers are fine (maybe a little more in the 15's than id like) but only idles very slightly lean. Under load and boost is fine when warm.

Im leaning towards a vac leak that wasnt noticed or the coolant temp sensor. Either way it doesnt seem to run very lean and is actually not even on the roads anymore so not that big of a deal to me for now.

And wht you talkin bout james? Its still on the road more than your gtr and your still plated! Lol

[Skym]

As far as I know, it should be into 12's? when cold (can go richer when in snowy conditions where coolant temp is colder). It's lean, but not 14-15 lean.

[fullthrottle]

After reading all of this I think you are all very silly. At idle and cruise it.can be as lean as it wants to as long as your car die. Under accel and wot is the only time you should care about your wideband. Your wideband is making you freak out about.nothing.

Sent from my SGH-T769 using Tapatalk 2

[evolution23]

After reading all of this I think you are all very silly. At idle and cruise it.can be as lean as it wants to as long as your car die. Under accel and wot is the only time you should care about your wideband. Your wideband is making you freak out about.nothing.

Sent from my SGH-T769 using Tapatalk 2

Basically what i said a few posts back i believe. Talked to a few shops they said people get their cars tuned to idle 16's to try and save fuel/hold temps/etc.. Once they told me that i realized my numbers are perfectly fine although it did seem odd that right after doing 100k servicing it suddenly stopped idling in 14's and started idling 15/16 but again, im not worried about this at all anymore as i know now im not damaging the engine (except maybe when cold as the car does hit 17's when i come out of my underground parking which has about a 45 deg incline... Only see those numbers coming out of parcade when cold though) but with the car being parked for now, not a big deal. Im going to probably be doing a lot of work to the car whileits parked for a few years so ill have a lot of tweaking/tuning to do when i finally get it back on the road anyways.