1997 4Runner SR5 - Idle Problems

W

werminghausen

New member
I bought a SR5 with some engine problems.
Car starts hard… takes some long seconds to fire up when cold.
And idle was warm @ 1500, way too high.
I then took off the intake rubber from air flow sensor to throttle body.
Took off the TB and replaced the Idle Air unit: the thing that controls the idle air flow in 3 stages : neutral (4mm open) closes (2mm open) and open (fully open).
I cleaned out the TB…there was some carbon residue but not crazy. I adjusted the stop for the butterfly with the vacuum pod ‘on ‘ (on vacuum). Butterfly closes well. Then put all back in place.
After replacing Idle Air unit the idle seems to be different but not consistent.
Engine starts with high idle (starting not any better..still takes a while to fire)…then gradually drops to 1000rpm…(much better than 1500..but).
But when I step on the gas and release idle will be back to 1500 for a two seconds and then it drops to 1000..sometimes even to 800. So there is a step now….1500…then 1000.

It seems to me that the Idle Air unit is still not working properly? It shifts not instantly. It sticks (high idle) then shifts (idle drops)?
What controls the Idle Air unit? What tells the thing what to do? Maybe something is wrong here?
Intake vacuum was 22”Hg at idle engine cold… I think okay.

Do people have any idea what to do from here?



Best, Martin
 
Register to hide this ad
what motor does it have? have you replaced the plugs, air filter, and fuel filter? those could help with the "hard start".
 
Did you use an aftermarket idle air control unit? If so, I'd say find a good used OEM toyota part.

You may have clogged injectors. This may be why it takes several seconds to fire-up. Try gumout fuel injector cleaner (one bottle fora full tank of gas, and you might need few rounds).
What I think why it takes several seconds to start is because the injectors may drop gas into the combustion chamber than spraying. When it is sprayed it is easy to catch fire.
(vapors are more flammable than liquids)
 
werminghausen said:
I bought a SR5 with some engine problems.
Car starts hard… takes some long seconds to fire up when cold.
And idle was warm @ 1500, way too high.
I then took off the intake rubber from air flow sensor to throttle body.
Took off the TB and replaced the Idle Air unit: the thing that controls the idle air flow in 3 stages : neutral (4mm open) closes (2mm open) and open (fully open).
I cleaned out the TB…there was some carbon residue but not crazy. I adjusted the stop for the butterfly with the vacuum pod ‘on ‘ (on vacuum). Butterfly closes well. Then put all back in place.
After replacing Idle Air unit the idle seems to be different but not consistent.
Engine starts with high idle (starting not any better..still takes a while to fire)…then gradually drops to 1000rpm…(much better than 1500..but).
But when I step on the gas and release idle will be back to 1500 for a two seconds and then it drops to 1000..sometimes even to 800. So there is a step now….1500…then 1000.

It seems to me that the Idle Air unit is still not working properly? It shifts not instantly. It sticks (high idle) then shifts (idle drops)?
What controls the Idle Air unit? What tells the thing what to do? Maybe something is wrong here?
Intake vacuum was 22”Hg at idle engine cold… I think okay.

Do people have any idea what to do from here?



Best, Martin
Click to expand...



Not sure what help I can be but I do know that the ECM controls the IAC. Now that gets it's signal from various sensors (engine Temp, O2 etc)

Never heard of the 3 stage IAC operation you were talking about, so that's all news to me, but I haven't had to service my IAC. Also, never heard of anyone adjusting the stops for the butterfly. I would think that if you did have to adjust that and it was never adjusted by anyone else then that would be indicative of another problem. I have read that some have had problems with the butterfly being off center in the TB bore and have had to disassemble the TB completely to recenter the butterfly.

One thing to be sure of is that you put the TB gasket on right. I think if it's not on it blocks a passage.

As far as you hard starting, that COULD be something else entirely or directly/ indirectly related to your idle problem, but if it wasn't I would look at fuel pressure first or maybe a bad fuel pressure regulator or , as someone else said, the injectors. Just giving ideas as this is tough to diagnose without looking at it.
 
Last edited:
Thanks, I bought a used Toyota part..no after market ...should work okay. But you never know. I am not so concerned about firing late at start up.... it will be probably ignition/injection as other people pointed out.

Martin
 
The story continues.

My wife was driving today and the car was worse than before...I thought.

It started idling at 2000 rpm! She did not hesitate and shut the engine off because it was so loud. I imagine if she had waited a few seconds the idle would have come back probablt to 1000. This happened to me too. 2000 rpm of course is frightening and I have not seen this before.

She then told me that this (the 2000rpm) happened to her before I fiddled with the Idle Valve unit.... so this is not new obviouslt. If she shut off the engine during super high idle the engine won't start easily again. This is what happened today.


So assuming this behavior (super high idle) was there before and had nothing to do with exchanging the Idle Air unit ...then at least I could see an improvement that idle will go down to 1000 or even 800 (before there was no way to get it down to below 1500)

Who has experience with the idle of the 3.4 engine? Why does the engine start idling with 2000rpm? I need to get this car going. My wife is frightened and hesitant now using the car with these problems.

Best, Martin
 
I did not replace the plugs or wires or fuel filter yet.
Will need to change the drive belt and with this I'll change a bunch of things.
The engine is running fine except for the idle problem and starting/firing issues. I assume the idle problem has not much to do with the starting issue?
 
Idle Air Valve adjustment?

I was looking at the Idle Air Valve which I removed yesterday..

I cleaned it out with Silicone oil and it works again! It was gummed up , partially at least.
After the clean up it works again.
The opening in neutral was about 1mm (still a mm-guy) measured with a caliper. And I saw that there is an adjustment possible... 2 screws opposite the magnets/3 pin receptacle.
I opened the 2 Philips screws and underneath I find the return spring that keep the flap to neutral or Zero. The cover plate for the return spring is sealed.. So I will use some sealant when I put it back.

The flap positions are as I described before... there are 3 flap positions:
Position One is neutral (defined by the return spring position)
Position Two is wide open (when Power [+] comes to one of the outer pins...middle pin is ground [-]...don't know which one...will check!
Position Three is almost closed...he flap closes almost (when Power [+] is applied to the other outer pin ..middle pin is ground [-].

My question to the experienced people: What is the set point of the flap?
How wide is the flap open in neutral (no power on the outer pins)

Tonight my theory is that the used idle air valve I bought is only partially functional...not much better than what I had before.
 
Last edited:
update Idle Air Valve adjustment.
The return spring position is not defining the flap gap at neutral as I thought.
It defines the resistance and opening size for wide open position.

I still think that with a fully functional Idle air valve my car will idle beautifully...
Let's see I'll install as soon as I can. tomorrow night I guess.
Martin
 
Idle is still shaky

Idle is still shaky after I put in the ‘old’ Idle Air sensor cleaned up… Same picture as yesterday.
What I did : I removed the ‘new’ Idle Air valve and installed the old one again and put all back together.
The engine started fine at 1300-1500. Warm idle was lower at 1000 when I put it in Park. After some seconds at 1000 rpm however engine starts speeding again…up to 1500…then probably 1800 then goes back to 1000 or even 800…then goes back up to 1500…. And so on. The change is idle speed happens in steps… it is not continuous. For instance 10 seconds at 1000 …then goes up to 1500 stays there for 10 seconds… goes further up to 1800… then the same thing back.
I think the Idle Air valve is fine but
something is fishy here: could it be that one input signal for the Idle Valve is faulty
Could this be the Air flow Sensor or Engine Temperature input?

Martin
 
First, check your vacuum hoses, make sure there are no cracks anywhere and all are attached. Then, as was mentioned before, have a look at your TB valve plate to make sure its centered and does NOT rub on the wall when closed. (My High Idle... CURED!!!)
 
Swede said:
First, check your vacuum hoses, make sure there are no cracks anywhere and all are attached. Then, as was mentioned before, have a look at your TB valve plate to make sure its centered and does NOT rub on the wall when closed. (My High Idle... CURED!!!)
Click to expand...

Mein lieber Schwede... thanks.

I checked the vacuum hoses around but could not find anything obvious, no obvious leak at least. Is there a more scientific method for finding a leaking hose? Best would probably be to replace all of them.

The TB butterfly closes very well, not as bad as the one in the write up.
Maybe it should be a tick tighter but not much.
The thing is now that idle will go down to 700/800...then after some 10 -30 seconds it will go up tp 1500-1800 and then after 10 -30 seconds back down to 700....and so on. What might cause this?

Is the ECM/ECU learning (I read something mysterious about the ECU). What does it learn really?
I was thinking replacing the Engine temp sensor... giving a signal to the ECU.

replacement of the vacuum hoses: can I just use standard straight hoses or would you recommend the Toyota formed hoses.

Can it be that the brake booster might be faulty? I had some minor issues during heavy braking while towing a trailer... I thought ohoh... it is hiding now without the trailer...but.

Best, Martin
 
I have the same problem. If I put it in drive and let it idle down the road, it still does it. At a stop light I have to keep my foot firmly on the brake.
 
Spray brake cleaner around the engine. Intake manifold gasket surfaces too. Any change in rpm is suspect. On American vehicles the idle air control is a stepper motor and easily unplugged while spraying so the pcm can't react to the spray. Don't know if that will work with the toyota.
 
update:

I installed the old Idle Valve with adjusted spring...and it seems to work now.
It idles now at 600-700 warm... 1200-1400 when cold.
I assume at this point it was the idle valve.
At least this is good news.. and I hope the idle stays that way.

I didn't find out if the engine electronics are 'learning' because idle improved now over the course of 2-3 days.

Now I another problem came up: drone during driving at 60 mph... car is humming and rattling loudly... I started a new thread.

Best, Martin
 
update Idle:

Car idles still badly especially if not really hot.
If it is hot (driving at least 10-15 miles) it mostly idles okay at 500-700.
Before the engine is hot the idle fluctuates. It jumps from 1200 to 1600 and then back 1200 and so on.

I have not sprayed the engine bay with carb cleaner in order to see if it is vacuum related.... But my logic says: if it were vacuum then it should be a constant high idle and not fluctuating (or how would you explain that it idles perfectly at 600 when hot).
This means something is giving the computer mixed messages...a changing signal? This signal is switching the Idle Air valve on and off.
What are the main signals for the computer at idle?

Engine Temperature
Air Temperature
Air Flow
???

In theory if the computer is working and the Idle air valve is working...then the signal does not work correctly?

Martin
 
Where are the people who know about this engine?

I admit my 4runnner is rundown but still it is a 4runner!
I resurrected it for the winter(lots of welding) and it drives great for a 'dead-called' car.... except for the idle.
Today it didn't want to idle even when hot.
So I need a plan what to do here. I hate idle at 1600rpm.

Need help.

Martin
 
You must log in or register to reply here.

Members online

No members online now.
Total: 304 (members: 0, guests: 304)

Forum statistics

Threads
278,309
Messages
3,554,068
Members
248,016
Latest member
Advally Service

Share this page

Trending content

Back
Top