TFOUR

So I bought a 1993 4runner 8 months ago that had 200k on the body. The previous owner had done a complete rebuild with new pistons head gaskets the works and had a tick in the valves. I knowing the valves probably just needed adjusting added some weasy cams (through Colt cams yes you can still get them) adjusted the valves to spec along with a host of other things.

So now the engine runs like a champ when the overall timing is set but has to idle around 1050-1100 rpm's to stay running. When done around 800 the idles fluctuate and the engine stutters. Timing is 10-12 degrees near stock. I put in a new TPS and also found that the AFM between E2 and Vc reads closed, with 5 ohms i recently have checked 4 rebuilt units and they all read similar.

Is it possible they all could be bad?? The stock fsm calls for 100-300 ohms. I'm wondering if their all like that or if that really is the root of my problems.

The exhaust is leaking at the cat not too bad, and the gas was a month old so i put in some stabil and half a can of octane booster for the whole tank. Next ill probably drain the gas. The only other thing i could think were the weasy cams need the afm to be adjusted from the get but they are designed to be stock replacements.

Other than that i'm not sure what else to check? Anyone have any ideas or knowledge about the AFM? I have done alot of searching but can't seem to find the answer's i'm looking for.

Thanks for the help any comments would be appreciated.

abecedarian

Depending on the cam grind, you may not be pulling enough vacuum to operate the VAFM correctly- for example if the intake pulses aren't smooth it could cause the VAFM flap to oscillate too much.

There is an adjustment screw on the VAFM, buried under a non-tamper cap, which allows you to bypass air around the VAFM which would in turn will give you some control over the air/fuel mixture at idle. It is similar to the idle-air bypass screw on the throttle body for adjusting idle speed.

TFOUR

Yea i'm hesitant to adjust until i know if the AFM is bad or not. Alot of the guys go two clicks and have better performance, but i have yet to see someone else have the same problems by not adjusting. The cams were designed to be factory replacements with no adjusting. I probably will try to adjust after i figure out if the AFM is good or not.

abecedarian

I'm not talking 'clicks' at all. There is a screw on the VAFM, near the duct that goes to the throttle body.
It may have a blank cover on it, so it would look like a circle with a flat, featureless insert.


it's towards the bottom/left side of the image above, just above where the duct would connect.

TFOUR

Oh that screw, well i won't be able to adjust it until I figure out if the AFM is good or not as right now i have a rebuilt one that I haven't adjusted yet. From all research I could not find anyone that adjusted it to make the cam specs and i'm hoping once i get a rebuilt one that it'll be set to the factory normal, I guess i'll save it for one of the last adjustments if nothing else will work. I'm hoping it's something i can fix without having to alter any factory adjustments. Thanks for the help!

Green93

I've noticed the same issues as you have. My truck runs great. Lots of power, but the idle is low and rough. I've tested and checked pretty much
everything. (although I didn't know about the screw on the VAFM) it seems to run the best with the timing way advanced. Almost off the scale advanced. Not sure if that is a sign of another problem, but for now it works best.

abecedarian

A problem with some cams is that they don't produce enough "vacuum", per se. This is a misnomer of sorts since they do produce vacuum. It's just that the vacuum isn't steady or consistant... it is lumpy, lopey or whatever you want to call it: it surges.
Allowing some air to bypss the AFM will smooth some of those pulses. I wouldn't count on it fixing everything though.

TFOUR

Green93, Does your VAFM give you a 5ohm reading between E2 and Vc, maybe you can try the adjustment screw while i'm looking at AFM's and report back my setup is almost exactly like yours bored 20 over just no valves.

TFOUR

Anyone else with any ideas?? Or that could check their Vafm on a good running car. Checked a different manufacturer same issue but another one of the contacts was out as well.

MudHippy

Resistance between VC & E2 should be 200-400 Ω(not 100-300 Ω).
http://personal.utulsa.edu/~nathan-b...92volumeai.pdf
http://personal.utulsa.edu/~nathan-b...04services.pdf

Mine reads 286.8 Ω for reference.

FYI, it's called the Idle Mixture Air By-pass Circuit. And, technically, it needs re-adjusted anyway. Since it was set at the factory based on the engine's performance in stock configuration. Which, obviously, no longer applies.

If you search around a bit you might find the thread where I described how I went about adjusting mine. If not...whatever...you'll figure it out...

abecedarian

You can't provide a link to your post?

I searched around a lot and couldn't find it. I searched some more, and with loose search terms, your first mention of it is in 2011. I've mentioned that screw as early as 2008.

MudHippy

Well, this might surprise you. But I felt your explanation of how/why it should be done was sufficient. Probably even more so than mine in this case. And, as I state in the post in question, it shouldn't be taken for granted that the adjustments I made to mine will apply to somebody else's engine. Particularly so in this instance since the engine's been substantially modified.

Anywho, I guess I should have provided a link. I apologize. And feel free to provide any due criticism of what I've said in it(which I'm sure you will).

TFOUR

Hi Mudhippy, thanks for your replies. I guess I am a little confused by your posts. In your first post you appear to be referencing the adjustment screw on the actual VAFM that the first gentleman recommended adjusting. In your 2nd post and your link you reference adjusting the Idle Adjustment screw on the throttle body and the A/F settings on top of the VAFM. I have spent a lot of time messing with the Idle Adjustment screw and can never maintain a perfect idle. It always fluctuates. I Have probably spent four hours on this. Could you please clarify your first post for me? I also checked out your links and realize that on the link given to me that they reference different terminals. http://personal.utulsa.edu/~nathan-b...33volumeai.pdf
That is what i have been using, I'm assuming its wrong. I won't be able to check against the fsm you posted till tomorrow.

*Slaps self over the head* it seems i pulled the 22re fsm page out of a link for a v6 without double checking it.

So once I install the new one i'm assuming i should try Mudhippy's method in his post first before messing with the actual screw on the VAFM?? Which is how I was doing it the first time?

abecedarian

If it's a lumpy cam (maybe "lopes" is a better word?) it won't pull consistant vacuum: there will be spikes in vacuum and lulls between the spikes.

The VAFM will be literally "flapping": swinging from open to nearly closed... and it is possible it may actually turn the fuel pump off.

You will have to increase idle speed on the throttle AND let some air bypass the VAFM in order to smooth the AFM signals to the ECU.

MudHippy

Oh boy...now what have I done?

Let me start again here.

I'm pretty sure the engine is going to idle considerably rougher than stock with those cams no matter what you do. And I don't know how much adjusting of whatever is going to help that. However the adjustments that I think might help are ignition timing, idle speed, idle mixture, and/or recalibrating the VAFM(VS circuit). But I don't know how much, or how little, adjustment of whichever may be necessary, or in what particular order you might want to try making those adjustments. These suggestions are all given under the assumption that there is an issue that needs corrected/is correctible, and that it doesn't have anything to do with a malfunctioning VAFM. And throwing out the notion that the valves simply need adjusted. Which may or may not be the case. But I wouldn't think that it would have an appreciable effect on the smoothness of the idle either way.

I hope that's clarification enough. Because that's about as simply as I could put it.

TFOUR

Yes That's clarification enough. Thank you both for your help. The valves are fin e took for ever to get them right. I will double check the correctness of the AFM, and I agree they are going to be lopey somewhat so I will not worry about that.

My main question was if their was a factory way to measure, the settings of the bypass on the VAFM and also what order to adjust the others. Since the Cam was designed for factory specs. I will put in the new AFM adjust timing and idle to factory specs. Then probably advance timing and see what happens. Most weazy cam owners notice improvement by adjusting. If there is no change i'll then go to the Bypass screw. Ill let you know how it works out.

abecedarian

As mentioned, idle speed will be affected by a lopey cam, so keep an eye on that too- you may have to raise your idle speed to get the results you want.

Adjusting the spring in the AFM is similar to adjusting the bypass screw. The difference mostly being that the spring is a coarse adjustment and the screw is a fine adjustment.
Adjust the VAFM spring one click, then see if you can get a good idle with the bypass screw. If not, bottom the bypass screw and adjust the VAFM spring another click, then see if you can get a good idle with the bypass screw.

I've you've ever tried tuning a carburetor with a 'cammed' engine, this whole do this, that, this, that, the other, go back and change that, the other and this thing will be familiar.

TFOUR

Ok good i'll try that I have a feeling I will be going back and forth alot. Ill let you know how it goes.

TFOUR

So today I swapped the gas out and insured the VAFM was correctly set and the car immediately ran better off the bat. I set the timing to 12 degrees and the idle to around 800. It ran slightly rough I didn't mess with the AFM adjustment yet just tried to see if it could run close to stock.

The IDLE would raise as the car's coolant got hotter. There are two issues i'm trying to correct. One the oil pressure seems low sits near the bottom of the gauge and never makes it half way unless i'm revving high. The engine only has 10 miles on the break-in period and i'm wondering if the oil pressure will be low until the rings seat. Also the motor overheats when it's idling, it ran ok while driving but as I slowed down it got worse. Fan runs fine, Both the coolant and oil are at normal levels.

I'm wondering if the overheating is partially due to break in and needing to adjust the settings talked about earlier. If there related to something else I want to fix them before I mess with it. I still have an exhaust leak dunno if that could be related.

TFOUR

So after doing a ton of searching here's what i came up with, for the cooling problem, possible bad thermostat gonna try the toyota unit and make sure it's at 12 o'clock positioning. Possibly needing to burp the coolant lines. And worse case that the headgaskets fot reversed, someone mentioned it's possible they will show a 1/4 of an inch on the backside if installed improperly anyone wanna confirm this? The radiator, water pump and thermostat are all new.

As for the idle, i noticed that the ECM does not drop the timing after pulling the jumper wire, i tried checking the IAC valve the engine does shut off when turned all the way in, I still have to check it immediately on start up. I am going to add a new fuel filter since I found out it has bad gas.

Other things on my list to check per the FSM are EGR, Oxygen sensor, Coolant temperature sensor. I will adjust the VAFM but i know the motor should not just jump 200 rpms because of the coolant. Anyone else want to add to my list or have some suggestions??? I feel like i'm almost their saturday is Dday.