Topic: Ethanol Free Gas, High Idle w/Surging

[jssgbsn]

During beginning of warm up to operating temp idle stays around 750-800rpm (Has been for a while now).

However, during the first few miles of driving the idle will surge from about 900rpm up to 1200rpm (idling at stop light, etc) in a rythmic 0.5sec interval.

Further into the drive, it will hold an idle between 1100-1200rpm.

If I blip the throttle a few times and get it around or over 5000rpm the idle will drop back down to the 800-900rpm range.  A few minutes later it will slowly start creeping up to the 1000rpm range, might eventually go higher but I couldn't sit and watch it idle for a ling time cause I was in a hurry.

I'm gonna see if the symptoms stay consistent and if I can duplicate the process every time.


I'm about halfway through my first tank of E0.  Anybody think this is a coincidence or has anybody heard of this type of symptom when going to E0.  This is definitely not in my head and is beyond noticeable.  Anything else that can cause this type of surging and high idle?  I don't wanna adjust the idle back down to 800rpm range since it would then drop it below the range to have it idle during the beginning of warm-up.

Something makes me want to think it isn't the E0, but it started happening right after my first tank of using it.

[helipilot77]

Need more information on your truck. Is it carburated or fuel injected? I have read that ethanol can really mess up carburated engines. It leaves a lot of varnishes on carburetor surfaces and can really gum them up. I don't know how that would specifically contribute to your symptoms. I would think going to ethanol free would only solve problems not create them. 

[jssgbsn [OP]]

Sry, 85 4Runner, 22RE, 5Speed

Agree E0 should help not hurt.

Curious if E10/15 causes a lower idle.  If it does then I can see how it would idle higher now on E0.

Just wanting to see if anybody heard of this before looking at any number of things that can cause surging.

[old runner]

Did you get it figured out? I switch between real gas and the crap with no side effects(except a better running rig for a little while).

You should probably run a few tanks through before you make any real changes.

[Wainiha]

Agreed, on needing more info on the truck.  What is it?

Agreed on no ethanol in the gas being better not worse.

My friend is dealing with this idle surge issue as well.  He has an EFI Nissan hardbody.  Here are the things we have do with no solution....

Changed:  Fuel lines
                 Fuel pump
                 Fuel filter
                 TPS
                 Spark plugs(new ones are already black and we can smell it is running rich)
                 
Checked: Gas quality
                Plug wires
                Vacuum leaks
                Exhaust and intake leaks

Need to check injectors timing and some other sensors.

What causes this?  I know most of us or Toyota freaks but the issues and solutions may be similar.

[jssgbsn [OP]]

Haven't figured it out yet.

I haven't had the time to trouble shoot much yet.

Gas Mileage is up from the E0.  I have let the truck idle for 20+minutes.  Definitely hits operating temp.  Stays idling at 750-800rpm the way it should.  But once I start driving the idle will jump to 1050-1100rpm under 'normal driving conditions'.

Same thing as before.  If I gas the throttle (clutch in) up to at least 4500-5000rpm and let off the gas it will drop the idle to 750-800rpm.  Once I start driving again the 'higher than normal' idle will resume.

My gut still wants to think it is something with the throttle cable or possibly fuel delivery.  But I have thought about some of the other things you have looked at already, vacuum/air/exhaust leak of some type. 

I'm sure I'll figure it out eventually.  When I make headway, I'll update this post for certain.

Thanks for following up and keeping me aware of problems, lol!!

[toyodaaddict]

next time it does this try sticking your foot under the gas pedal and push up on it. If its in the throttle linkage/cable this might make the idle go back down and let you know where the problem is. My DD (84 toy) idles at 800 but from time to time when I come to a stop the idle will hang at 1000, if i pull up on the pedal it drops right down to 800. it happens so rarely I never seem to get around to fixing it.  If the vehicle in question is carbed and the idle surges when stopped try replacing the o ring on the idle fuel cut solenoid. get one from toyota not the hardware store.

[jssgbsn [OP]]

I'll try that on the gas pedal next time I am out.  Hopefully that is it!  Will save me some troubleshooting time.  (EFI tho)

[jssgbsn [OP]]

Not sure how but the nuts where the throttle cable terminates (throttle linkage) at the intake backed away a thread or two.

I pulled them back, drove around and it seems to have solved the high throttle issue. 

Haven't had an issue at start up either...yet. 

http://board.marlincrawler.com/index.php?topic=88811.0

Pics are already in the post above.