idle AFR fluctuation 12.1 or 14.6

[EclipticalGS]

I just sort of noticed this, but my aem wb02 has a fluctuating idle afr.

Ill start it up once a day, the idle will sit at 14.7 all the way till my car warms up, ill drive around and come back home, then it will sit and idle at 12.1....

But when i take a drive while my idle afr is 12.1, the car still acts the same and has the same cruising afr's, and wot afr's. Just my idle afr's are different.

Today i started my car and it's at 12.1...shut i down, went back out and started it hour later, its idling at 14.7..

No CEL's

Timing is 5 deg. BTDC

Idle is very smooth @ 750-800 rpms.

As far as i know all my sensors are fine.

wb02 is calibrated

It's 15 degrees out, but my garage was all warmed up at the time i stared it


I do not have a way to check 02 voltages yet, until my logger cord comes.
Havent replaced my Coolant temp sensor either
Power to the wb02 is off my turbotimers extra 12v wire
Noticed coolant drips on my front 02 pigtail (on top of transmission, when i opened cap)

Any inputs appreciated, just trying to figure this out.

 

[viprez586]

Double check all of your wiring, the AEM UEGO tends to get hot - at least mine does. Otherwise maybe a faulty sensor.

Check all connections, make sure they're soldered and insulated as to not be shorting to ground or other wiring. Disconnect the sensor connector, clean if necessary and put a little dielectric grease in there to keep things tidy.

One of my wires happened to be coming loose a while back (due to living in a bad neighborhood, I'd take the gauge out at night). Anyway when the connector on the back of the gauge wasn't inserted properly I'd get a solid reading in the 14.xx to 15.xx depending on conditions.

If you still have problems do the wiggle test and watch the gauge to see if you have any breaks/opens in the wiring.

 

[Sp1kE]

I find it takes a bit for the sensor to warm up or something. It will sit at 14.7ish while cold even if im dumping ungodly amounts of fuel into it.

I'd say your car is just running rich.
Let your car sit there and warm up for a long time without driving it, I bet once its fully warmed up without driving it, the gauge will read in the 12's

 

[BIRDCLAWTSi]

what are you using for fuel control? safc? link? it didnt state in your profile. i have an afc and the uego, i have to pull out like 10% when i cold start, otherwise is will be rich until it is warmed up. once it goes into closed loop it will try to maintain 14.7:1, and you can test the 02 voltage with a dvom.(voltmeter) the two wires that are the same color are either the heater circuit or the 02 voltage, but that is how they are paired. the two white or the gray and black, you will know the difference once you connect. hope this helps.

 

[EclipticalGS]

Yeah I checked all my connections, I used one of my turbotimers extra 12v wires for gauge power, then i used a ground off somewhere in the center console. The ground is the same ground my turbotimer uses, the ground was tested for continuity and is fine.

I pulled the gauge while my car was FULLY warmed up, i wiggled both the 02 harness and power harness. No change, my idle afr sat at 12.1.

I do not "tune" with anything yet, im breaking in the motor. Im running 10psi, the car acts very good on/off boost.

Vacuum at idle is sometimes -18 and sometimes -20. Not sure what that means.

The weird thing is my cruising and WOT afr's never change. It's only the idle.

Makes me think my car either had a:
*Boost leak/vacuum leak
*bad front 02
*bad temp sensor, but why do i "sometimes" have good afr's

Could it be that I disconnected my Fuel pressure solenoid?? (I have vac line straight from IM to fpr)

Thanks

Also...my car will idle at 14.7, but then i take off for 5 minutes, getting into boost, and when i pull into my driveway, my afr's will sometimes hover at 13.6, then they will gradually make their way down to 12.1 to stay for the remainder of the car being on????

 

[Sp1kE]

Maybe that walbro 190 is overrunning your stock fpr?
And it takes a bit of time for it to overrun?
Has the idle afr ever went back down to 14ish after driving?
That could also explain when you let it sit for an hour and come back out it will read 14.7 again. Because of the pressure bleedoff.

Try a afpr or the stock pump?

 

[EclipticalGS]

hmm.. that could be it....

Because After driving and it idles at 12.1, if i shut the car off and start it in 5 minutes, it's still at 12.1.

Hours later if i start it, it idles at 14.7 again, then after a drive, it'll be back down to 12.1.

But wouldnt the pump over-running my fpr cause rich trims at cruising and wot??

 

[viprez586]

What are you tuning with?

I agree - sounds like FPR over run.

 

[jeffo]

Get your logger working and check the fueltrims. That will help a lot, especially if it is FPR overrun.

 

[EclipticalGS]

Couldnt I just check fuel pressure when its idling at 14.7 and then check it when its a 12.1 and if theres a difference Ill know its being overrun

 

[viprez586]

Couldnt I just check fuel pressure when its idling at 14.7 and then check it when its a 12.1 and if theres a difference Ill know its being overrun

No. Over run is the FPR diaphragm is not opening enough to let extra fuel dump back to the tank.

What are you tuning with?


I have slight over-run. I'm using SAFCII and I have to dial back -20 to get my fuel trims close to 100% aka 0%.

 

[EclipticalGS]

im not tuning with anything at the moment. I am running 12 psi, during a breakin.

I have a 190 and i never thought it could overrun the stock fpr.

 

[GRAVEDIGGER]

A 190lph pump will not overrun the fpr from what I have seen so I don't think that's your problem.

 

[EclipticalGS]

Ok I went out to my car today, started it, it idled at 800 rpms, afr when the car was fully warmed up was somewhere around 12.6-13.1 now??? Then when I took a drive, came back, car was idling lower than normal, it was now idling at 650rpms but still a very smooth idle, and afr was dead set at 12.1

I will try it tomorrow and see if it idles at 14.7 ever again..If it doesnt it has to be a sensor of some sort..

I just rechecked timing marks, and timing is dead set at 5* BTDC

Im not sure what to check? 02 voltages?

Thanks

 

[edsgst]

I had the same type of problem recently, and it was the coolant temp sensor.
My AFR's would stay in the 11's and 12's at idle, but cruise would see 14's and 15's.
It apparently wasn't going into closed loop at idle.

Although it didn't throw a CEL, I had it scanned, and the culprit was the coolant
temp sensor. One second it would read 195*, like it should, then the next it would read 40*. Whatever...

Anyway, I swapped it out, and the idle returned to a normal 14-15 AFR.

 

[Never Satisfied]

If you did the rewire for thd fuel pump, either before or after installing the 190, you could be over running the oem regulator without much difficulty.

 

[EclipticalGS]

Yeah, coolant temp sensor has helped me in the past, I might as well try, ill post back up afterwards!!

Also, any reason to replace my coolant temp switch? or is that just for my temp gauge.

Thanks.

 

[viprez586]

im not tuning with anything at the moment. I am running 12 psi, during a breakin.

I have a 190 and i never thought it could overrun the stock fpr.

Ok, so your running a rewired walbro 190, and 550cc injectors.
Your not tuning with anything. Meaning no MAFT, no SAFC, etc.

Your going to run rich!

Like I said, YES - it is possible to get over-run on a 190 - do a search on members who've had it happen.http://www.dsmtuners.com/forums/newbie-forum/293397-running-rich-450s-190-pulling-fuel.html

Second of all if you have no way of tuning the ECU is trying to correct for this added amount of fuel and it cannot. The ECU can account for 5% to maybe a max of 15% of fuel being delivered. Third - some first hand experience like i said - I have a walbro 190, 2g maf, 550cc injectors - same sh_t. I dialed in my SAFCII 20% richer to get my fuel trims happy(aka 0) and pull a nice steady 14.7-15.3AFR for idle.

 

[EclipticalGS]

Well why does my car dle at 14.7 and cruise at 14-15 all day long. But only SOMETIMES it idles at 12.1??

If my 550's and non-rewired 190 were over fueling me, i would not get 10.6-11 WOT or 14-15 cruising would I?

Also, just to clarify, anyone have a pic of some stock 450's?? I cant trust previous owner saying their RC 550's lemme take that off my mod list too.



EDIT: I have found that they are not RC 550's by any means, they are most likely stock 450 injectors.

So, I have 450's, a 190 fuel pump (NOT rewired), Stock fpr.