Over revving on start up

[aboulsimm]

Hey all,

So when I start my engine, 50% of the time it over revs before returning to normal idle...by over rev I mean going up to 3k rpm or a little above.

Doesn't sound normal...and seems a bit harsh on the engine while still dry!!!

Anyone had that before?

Cheers

Sam

 

[kidglove13]

Thats extremely high 3k really?
I have read about high idle at start around 1800 rpm
Throttle body probably needs to really cleaned

 

[Frankencruiser]

Definitely have a problem. What year is it?

 

[aboulsimm]

it's a 1996 1-FZE engine ...around 240k km on it

 

[retrofive]

1800-2k seems to be normal, 3k no.

What maintenance has been done?

 

[aboulsimm]

All regular maintenance done...that's how it was acting since I bought it used!

 

[71fj40cruiser]

Check your idle air control valve---make sure it and the bore is clean, free from carbon. Check the o'ring also

 

[JohnR]

I know what's wrong! hahahaha. Sorry.

I recently rebuilt pretty much every aspect of my fjz.. including new marine style battery terminals for the pm-1. I 'cheaped' out on doing it, instead cutting / boring out the stock positive cable lugs to fit the 3/8" stud, including the fusable links. Well, I started it up,and it would rev to 3k-3.5k and IDLE there. No matter what I did. Turns out, if one of the fusable links ISNT making contact correctly, it will do that. I removed all of them, scuffed them up, and put them back down on the terminal. It now starts and revs to 1,100rpm and settles down to 650 within 5-10 seconds. Check your links / battery terminals!

 

[JohnR]

Forgot to add. I overtightened a marine terminal, and cracked it, so I had to replace it the other day. Went bought the replacement, and installed it outside advanced.. went to start the truck, rev'd to 3k again. Loosened the wingnut, wiggled the wires, then tightened it down again. Problem solved! I'm pretty sure it's the link that has 2 wires going to the same terminal side by side that is giving the problems, so check that!

 

[71fj40cruiser]

Every time you disconnect the battery the ecu must do a relearn. Usually if you have an idle problem (due to something else) disconnecting the battery will cause the idle to relearn, it will go to a low rpm for several start-ups and then go back to high idle if the problem is not fixed.

Hope you got it fixed though

 

[CJF]

Next time it happens, pop the hood and see if you can cure it by manually closing the throttle.

 

[Jimkost]

Hi all. I know this post was started in 2011 but I don't think it was resolved.
It was good for me to see that someone else was having the exact same issue is me with the engine reving to about 3000 on start up and quickly dropping to normal tickover.
I have fixed mine. I have a boat with two Toyota 3L turbo diesel engines. Both my engines developed the problem this summer. After months of trying I finally found the cause.
It was the turbo pre boost. The thing on top of the injector pump with 4 screws and a diaphragm.
Take out the 4 screws. Remove the diaphragm and pin with the groove in it. Look inside and you will see the small thin pin sticking out. It needs pushing back. Mine was stuck and caused the pree boost to be at maximum all the time. I had to temove the 17mm bolt with the small spring inside to enable the pine to be pushed back. Re fit every and it should have stopped the high reving at start up.
I think I caused my problem by over reving the engines while chasing dolphins.

 

[SpenserAK]

Mine always cold idles around 1300, then down to ~1000 after a few minutes. Fully warm, low 600s in drive, mid-upper 600s in park.

After doing my VC gasket, PCV & hoses (all OEM), it "flash" revs to maybe 1600-1800 at first on a hot re-start, but immediately settles to normal. On occasion hot idle in drive will barely dip under 600, but never feels weak and is nicely smooth.

TB & IAC are clean, wondering if I have a tiny crack in the big intake hose after removing it a variety of times, despite not tugging/bending it. Cable is adjusted properly, etc. Hmmm..

Not worried as it's so mild, just interesting something changed a hair. Haven't done any testing yet.