PitMyShants

Hi all. Posting for a friend here, trying to get his truck more... mobile

Friend has the following symptoms:

• truck starts fine cold
• after 20-30 minutes, truck will notice a wandering idle
• not long after the truck will stall out
• truck seems to work fine in gear and on the throttle
• truck doesn't want to start after stalling out while hot

My first thought + bit of research here and elsewhere.. seems like an issue of fuel/air. After reading my plan is to..

• Get the vehicle up to temp where issue occurs, let it stall
• Try jumping the wires that go into the circuit opening relay (COR) to bypass the AFM and run the fuel pump; if it starts well, I know I have an issue with the AFM or the COR; if not, cry (maybe check fuel lines to see if they're properly heat insulated)
• Replace COR to it's wiring. Remove starter solenoid wire and listen for COR clicking while turning the key; if no click, probably a bad relay; if clicking, try to clean AFM/MAF
• Clean the AFM/MAF (WITHOUT TOUCHING THE SCREWS!! that are visible here)
• If no start after spraying cleaner, open the top of the AFM and ensure contacts are making a good connection (seen
  here
  )
• If no luck after this, check the intake boot for any air leaks. Is there a way for me to test by blocking something to see if it starts better?
• Lastly, maybe replace the O2 sensor? I get stuck here..

Am I missing anything? Did a couple hours of google-fu around here, 4crawler, and toyota-4runner.org. Essentially I should know after jumping the fuel pump if it's COR/AFM related. Doubt it's COR related as I would think I'd have issues starting cold. Wondering what I could be missing but will give this a go tomorrow. All help appreciated

snippits

Test the ECU temperature switch...not the temperature gauge switch. Also, I would take a look at the idle air control. Pretty sure yours is different than my 92 22RE.

coryc85

I think I am with snippits here on this one, test the temperature sensor, as he says, not the gauge one but the ECU temp sensor. Some people have also reported idle fluctuation due to air pockets in the cooling system, so might be a good idea to burp it and make sure there is no air in there, search this site for how to burp cooling system. Also, I would check for a vac leak, look hard at the EGR vac system, because that one in particular I believe only starts applying vac after engine warms up. Also make sure EGR routing is all correct.

Any more information on this truck? Like did it run completely fine and this problem just recently started happening or has this been a long standing problem that has never been fixed. Sometimes if there was recent work done, like for instance someone replaced all vac lines, then I would look very closely at the vac line routing to make sure it is all correct.

And last thing, I would not open up that AFM and do anything to the guts unless you absolutely knew for certain it was a problem....and I don't think we are there yet.

PitMyShants

Is this is what I should be looking to test? Any documentation on how to?

https://22reperformance.com/22re-eng...cu-temp-sender

Not really sure what I'd be looking at as far as the idle air control. Any more reading on this? Wouldn't something bad here also give me issues before getting hot?

As for other info:

• He said that the radiator was replaced by a shop, so I assume it was bled properly. Will go ahead and burp it again anyway.
• He has had the truck for less than a year, but the problem started a few months after he got it.
• He said truck can be a little bit harder to start in warmer temps (even with a cold engine)
• Not noticing any oddities in the coolant temp gauge, doesn't seem to be overheating..

Going to check out a bit more in person today and will report back.

coryc85

Link to the 1988 4Runner Factory Service Manual : https://web.archive.org/web/20110102...4runner_88.pdf

The FSM has detailed specs for the resistance of the temp sensor at temperature. The general idea is to heat up some water to a specific temp, soak the sensor in it and measure resistance, do the same at normal ambient temp. Compare resistance to the range in the FSM.

snippits

On my 92, I would get sporadic idle when the engine was hot only. It would idle up and down, idle too high, but it did not ever die. And it was just random when the engine was hot. Idle air control was bad. Never did it again after I installed a new one, and that was years ago.

coryc85

On the 1988, the Idle Air Control Valve, or I think sometimes it is called Aux Air Valve or something like that, it sits under the intake, it has 2 small coolant hoses going to it, and it has in and out air lines, one feeds into side of upper intake plenum, and one comes off side of the throttle body. At ambient temps it should be open to allow air to pass through it, then as the engine warms up and coolant flows through it, that little wheel inside it should move and block off the extra air flow. There are some on vehicle tests sortof. I believe one of them is to start up the vehicle and then while cold, pinch the air hose closing of the extra airflow, and engine should stumble, if it does that means that engine was pulling in extra air and you pinched it off, if engine does not stumble, then the IACV is likely closed at cold engine temps. Then when engine warms up, do same test, this time though, in a working system, engine should not stumble because IACV should already be closed.

Download that FSM, it will tell you all of this in greater detail.

snippits

Yup I thought the 88 was different than the 92. Thanks for clarifying that. Not sure if bad part symptoms would be the same as 89 to 95 IACV.

lledwod

iTrader: (2)

Could your TPS be out of adjustment?