Idle adjustment question

[Burntboot]

I know this doesn't help you, but it sure is nice to know that I am not the only one in the world that suffers from odd problems, that aren't easily resolved.

Last straw in the box
- How is the transmission mount (aka rear engine mount?)

[MyToy]

Yeah, same goes for me. I am honored to be part of the club


As for the mount.

It sucks. It is the one weird one that mounts from the top with a single hole for mounting.

I was going to change it but could not find.

It looks like this. It has some cracks and is no doubt original.

[MyToy]

Just wanted to keep all of you updated on my idle issue. The plan was to install a wide band O2 sensor and mixture gauge so I could adjust the mixture correctly . Well to get that done a Bun has to be put into the exhaust pipe. So I went to a shop and they noticed that I had a leak at the junction from the front exhaust pipe to the manifold assembly. Turns out the meat ball that install this warped the flange that mounts the pipe with will cause the donut gaskets to fail in less then a year. So I have to fix that first. Can't find one anywhere. So my intension is to remove it and bring it to a machine shop to have the flange replaced or planed. Once completed the bun will go in an I can make my adjustment.

Just wanted you to know I have not died yet

[MyToy]

VanCo and crew, the verdict is in. Installed the Wide Band sensor as instructed. See photos.

When first started or idling it showed 18 to 19. 19 is the max the WB D2 will go.

Then, once on the road and cruising down the highway it drops to 14.6.

Any thoughts on this? Is the rich 18 to 19 screwing up my idle? If so then if adj correctly I would screw up my cruise, right?

[VanCo]

The higher the number the more lean. For example 18 parts of air to 1 part fuel vs 14.6 air to 1 fuel. More air is leaner. Anything over 16:1 at idle on these engines causes a sporadic lean misfire. 18:1 would cause a pretty bad idle, and it really wouldn't want to run.

Usually with readings like yours you want to look for vacuum leaks first as well as a host of other things. 99% of the time that's the issue, but I know the back story so we can go straight to messing with things the factory says not to touch.

First, when cruising does the wideband bounce extremely quick between 14 and 15, or does it just sit at 14.6? When floored for more than three to five seconds does it go into the 13 range? When cruising and you lift off the gas (deceleration) does the air fuel go into the 19 range? These are important details that help determine if the computer is controlling the fuel in open or closed loop, and if the TPS is working correctly.

The AFM has and idle air fuel adjustment. It's technically the only "serviceable" adjustment on it. This adjustment does slightly affect cruise, but only if a drastic change is made. Also, whatever change is made the ECU should compensate in closed loop.

There is a small round aluminum block off cap on the top of the AFM. Pop that off, I drill a small hole and pry it out. There is a flat head adjustment screw inside. This screw basically allows air to bypass the metering vane. Essentially it's an intentional vacuum leak. Close off the airflow here, more metered air, which means more fuel. Open it up, less metered air, less fuel. I don't remember which way is what. I like to write down how many turns it currently is from fully bottoming out. That way I can return to factory if needed.

The computer controls the injector pulse width within a given (small range) percentage to achieve a stoichiometric air fuel. The base starting point for this is the fuel table (what it directly references for open loop running). If the deviation between fuel table and reported air fuel is too large, the ECU cannot compensate. When setting the idle you need the ECU to supply its programed pulse width, and not be trying to compensate as you adjust.

I would only make the adjustment if you know the computer goes into closed loop when warm (but is not currently in closed loop). Also, you want to adjust it to 14.7 in open loop, fully warm. The best way to ensure the computer is running in open loop on preprogrammed perimeters is to disconnect the oxygen sensor while making the adjustment.

As a best practice document all changes in detail, just in case you need to undue what you did.

In addition, do not freeway cruise or wide open throttle at anything above a steady 15.0. oscillating up to 15 and back down is fine. You just don't want to run it loaded and lean for any amount of time. Doing that can mess up engine internals.

[MyToy]

Thank you for your input VanCo. I don't want to tell you what I went through to get that Bun put into the exhaust pipe. Wow, the amount of data learned from this exercise is fantastic.

I guess I must have got the number wrong. So now I know, low is rich and high is lean.

I will have to get all those numbers for you today. I will log them down as I use the van.

I will get as much detail as I can.

Thanks !!!!

Mt

[MyToy]

VanCo:

Ok, did another run of tests both to and from work yesterday.

When cruising it is pretty steady at 14.6. Ever so ofter it will pop up to 15 but not as much as it pops down to 14.5.
When floored for 5 seconds eventually will hit 13.
When let go it very quickly goes to 19, then to 18 and back and forth.

Then of course at idle she will stay at 19.

What is your take on that?

MT

[VanCo]

Everything sounds good (except idle), though it's interesting that at cruise the readings don't bounce back and forth more often. This could be due to the placement of the wideband O2 bung, which is fine, just interesting.

There is a way to monitor the reading coming from the factory O2 as well. You can tap into the signal wire going to the ECU and connect it to a narrowband O2 sensor. I had both a wideband and narrowband hooked up when I was tuning my AFM. This told me what small changes the ECU was making to try to achieve the proper air fuel (and that meant it was in closed loop), and the wideband told me what the air fuel actually was. With this information you can lean, and richen until the ECU cannot compensate any longer. This helps determine the limits of the ECU so that you can tune the middle of these limits. I don't think a narrowband is totally necessary, but it is useful and interesting. It's also useful in determining the health of your oxygen sensor.

Here is a video from a few years ago. In it I touch on the wideband and narrowband. Don't pay much attention to the specific readings; this was post severely modifying the AFM and fuel system. It wasn't perfect by any means. https://www.youtube.com/watch?v=pJduqIX3n0Y

At this point you could unplug the factory O2 sensor, warm it up, and drive around to compare readings. With the O2 unplugged it should run more rich at cruise than when the O2 is hooked up. This forces the ECU into open loop, and to use the preprogrammed fuel table only.

You can also pop that idle cap of the AFM and try to get that idle number to 14.7 with the factory O2 unplugged. Just document changes to the screw.

Most wideband O2 controllers have a PC serial connector so that you can log your drives using a laptop. Making that feature work might be helpful too.

[MyToy]

Nice video VanCo!

OK kind of sorta worked. Did what you said and removed the O2 sensor after van was hot, right after highway driving. Removed adjustment cover, just popped that baby off just like you said.

Counted my rotations, 3.5 turns to bottom. Backed it off, ran the van. Let it stabilize a bit and went for the adjustment. It was not super effective but it did reduce the idle mixture to about 15.5 after letting her settle down. Howeve; that is with the adjustment all the way down. Can't go no more.

The idle went up a bit. Reconnected the O2 and it stayed about the same. Took it out on the road and she continued to run very smooth at 14.6 at 80MPH. Stopped to idle and she hung in there about 15.3 to 15.5. A hell of a lot better than before. Need to do a lot more driving to see how it response to the shaking. I am going to reduce the idle down to see if the shaking remains. Will let you know.

MT

[MyToy]

Final on this chapter. The mixture adjustment that VanCo brought to the table has worked remarkably. I was almost ready to throw in the towel and just live with it. But now, after a week of use, it maintains performance at idle and the heat soak issue has reduced by almost 80%.

Job well done. Now it is off to my next improvement and that is the hard ride. I am off to the suspension areas of the forum.

Thanks Again
MT

[timsrv]

[VanCo]

Super awesome! I'm glad it helped!

[Toyota2RZ-E]

I had a similar problem turned out to be leaking diaphragm within the aircon idle up vacuum device 88606D located on the throttle body.
Took some time to find.
Suck on the hose connected to the vacuum chamber of the device, there should be a vacuum ie no contentious flow of air.
Regards Mike