rheilman

Hi there, Hoping someone can help shed some light on a strange problem my Toyota is having.

The truck is a 91 4x4 22RE. For the duration of my ownership the truck has ran like a champ, with only a few small quirks.

For a long time the temp gauge would only go up to 1/8th, and only after a lot of highway driving on warm days at that. Also the heater would only blow mildly warm air. When the truck was as hot as it could get (temp gauge at 1/8-1/4 of the non-red portion of the needle sweep) it would stall out if I let it out of gear. I can keep it running with my foot just barely on the gas. This would only happen when I had been running at highway speed on a warm day. During normal driving, even when warmed up, the truck was not stalling. (Infrequent enough not to be a big deal)

I checked the temp sending unit and the gauge, neither of which seem to be the problem. A friend suggested the thermostat might be stuck open. I removed the stat and sure enough it was stuck open. Got a replacement, and installed it.

Heres where it gets wierd.

Now the truck heats right up, with the gauge about in the middle of the safe operating range. But it now stalls out regularly when its up to the now higher running temp. I also hear a click coming from the glove box area when its about to stall, and when I try to keep it alive with a foot on the gas, I can also hear the same click.

Maybe something to do with the idle or some temp sensor other than the one for the sending unit?

Any ideas of where to start poking around would be appreciated.

Cheers
Ray

rheilman

Bump... Someones gotta have a clue for me!

sb5walker

The click is from your circuit opening relay, which powers the fuel pump. The fuel pump switch, which is in the air flow meter, is intermittent, either because you have a leak in the air hose that goes from the meter to the throttle body, or because the contacts of the switch are messed up.

Check for cracks or leaks in the hose, and if you don't find any, you'll have to cut the silicone around the black plastic top of the meter to try to clean up the contacts and perhaps you'll need to bend one of the contacts a little bit. Look in the fsm for which two contacts are for the fuel pump switch, (the left two, IIRC). There's a thread or two on it, also. If you do open up the air meter, be sure to seal the cap with silicone when you're done.

http://personal.utulsa.edu/~nathan-b...33volumeai.pdf

sb5walker

I couldn't find the thread with the person who fixed the fuel pump switch but here's a post with pics showing the inside of the meter. In this post, a different terminal is broken, not the fuel pump switch. But you can see the two tabs of the FP switch on the left side of this pic (not the red circled part):



And you can see the two tabs better on the right side of this pic (BTW do NOT remove the terminal like this poster did):



You can see a metal bar attached to the black plastic in the top photo - that bar pushes against the longer tab of the switch, keeping it away from the shorter side. When the vane of the meter is opened by the air being sucked into the motor, the long arm pulls away from the long tab and it springs toward the short tab, making contact and closing the ground, completing the circuit between the FC lead from the circuit opening relay and E1, which is a ground. So if there are no vacuum leaks in your air hose, then maybe the long tab has lost its spring.

From this thread: https://www.yotatech.com/forums/f116.../#post51233798

BUT. Most likely, the problem is a vacuum leak in the air hose. Even a small one would cause your problem. Probably the reason it happens when the motor is hot is that your idle comes down, and there is less air flow, so all the air can come in through the leak, bypassing the vafm and therefore not closing the fuel pump switch.

rheilman

Sb5Walker,Thank you so much for the detailed response! This seems to be a very likely scenario, it perfectly explains my symptoms!

I checked out the vacuum line this morning, and there is no visual sign of a leak, Ill check it more thoroughly when the weather is not so rainy, and if nothing turns up Ill head to the inside of the AFM and inspect those contacts and mechanism.

Thank you again, and Ill update when I figure it out!
Cheers

sb5walker

Just want to make sure we're talking about the same thing. A "vacuum line" usually refers to a small diameter (less than 1/2") rubber hose used to apply vacuum to something. It doesn't usually have much if any air flowing through. I was talking about the large diameter (about 4") plastic/rubber air hose attached between the VAFM (air meter) and the throttle body, through which the engine sucks air.

Just wanted to be sure.

But speaking of vacuum lines, it is possible that another vacuum leak somewhere else could cause the same problem. So I would check all of the hoses/tubes attached to your intake. You can pass an unlit propane torch or spray starting fluid around the engine while it's idling and listen for an increase in RPM.

There is a check you can do which will give you some more info. First, check that the rpm does in fact drop when the motor becomes warm. That indicates that the cold idle bypass valve (called the 'auxiliary air valve' in the fsm) does in fact close when the hot coolant hits it. Then with a flat blade screwdriver, screw the idle adjustment screw (the big flat head screw on top of the throttle body) all the way in. The motor should stall. If it continues to idle with the idle adjustment screw all the way in, you have a vacuum leak somewhere downstream of the throttle body (in other words, something attached to the intake is leaking air). (It's also possible some ignorant person has adjusted the throttle stop screw which should never be touched.) If it does stall, then you should check that air hose more thoroughly - there's a good chance of a split in it somewhere. The rubber bends are most infamous.

Unscrew the idle adjust screw out the same number of turns after your test to restore normal idle. When you complete your search for (and fixing of) vacuum leaks, and with motor hot, set the idle to 750-850 rpm (spec is 750 for manual trans, I think auto is 800 or 850, but you can set it wherever the motor runs the smoothest. Just don't exceed 850-900 rpm or you run the risk of introducing the dreaded 22RE idle surge problem.

Because the problem occurs mostly at low RPM, I think a vacuum leak is a more likely cause of your trouble. But it is possible to be the fuel pump switch contacts, too.

Good luck and let us know how you make out.

rheilman

Ok, so I finally got around to digging a bit deeper on my idle problem. My alternate vehicle has been running well lately, so that has taken some heat off of my tinkering with this idle issue.

SO, I checked all the vacuum lines leading into the throttle body area. No problems there. Checked the intake hose for cracks and leaks, found none. Checked to make sure the air filter was clean and installed correctly.

After a bit more digging around and finding nothing out of the ordinary, I decided to try the obvious and simple solution. I raised the idle enough that the truck would not stall when warm as it had been doing.

I was concerned that this would raise my cold temp idle too high, and although it is higher than I like it, it is not unreasonable. I dont have a tach so I cant be sure just what the idle is at when warm or cold. The truck heats up quickly enough that the high idle at cold is not a huge deal.

She runs well now and has not been stalling out even when at full operating temperature. My only concern is that I have not really solved the problem (assuming that there really was one to begin with) and raising the idle only compensates for some other problem.

I have yet to put a whole tank of fuel through it, but next time I fill up I should be able to determine mileage and maybe that will at least give me a clue if something else is amiss.

Thanks for helping me troubleshoot this! Will post back any further findings...
Ray

McAtee

I am experiencing this same issue, and have also performed the "band-aid" approach by turning up the idle so it wont stall out. If anyone finds the fix action to this please let me know, I have almost gotten into a couple wrecks from stalling out.