throttle body & idle trouble

[toad660]

Hi i have got a Evo 8 and have a problem with it the last 2 weeks, took the throttle body off to clean out ,refitted it and it will only idle at 1200 rpm now.changed the stepper motor no change, reset the TPS with evoscan no change , no air leaks , i havent got a clue why its refusing to idle at 850rpm, the only time it idles at 850rpm is when i run evoscan and press actuate it drops to 850rpm but when i come out of evoscan it goes back up to 1200rpm..................is there anyone that can help cos its doing my head in..................lol......)

 

[mark]

Hi i have got a Evo 8 and have a problem with it the last 2 weeks, took the throttle body off to clean out ,refitted it and it will only idle at 1200 rpm now.changed the stepper motor no change, reset the TPS with evoscan no change , no air leaks , i havent got a clue why its refusing to idle at 850rpm, the only time it idles at 850rpm is when i run evoscan and press actuate it drops to 850rpm but when i come out of evoscan it goes back up to 1200rpm..................is there anyone that can help cos its doing my head in..................lol......)

private message el
he may have one ray

 

[sponners]

did you disconnect the battery after setting base idle?

 

[toad660]

yep disconnected the battery for over 1 hour after reseting the base idle and throttle position sensor and it made no difference.........its got me pulling my hair out........i am starting to think the fast idle valve isn't working and is stuck open............all this from just cleaning it.........lol

 

[toad660]

now then mark who's el.........????????????

 

[Nickygixer-k5]

now then mark who's el.........????????????

El Dopista

 

[ElDopesta]

I think you need to get some tech help from the Geeks before you spend money on a Throttle Body/ICV/TPS.

I am quite convinced that you will be able to reset the base idle as I feel that you have missed something out.

I am sure that Sponners/HermaN/Simon or Rob will be able to GroupGeek and arrive at a conclusion that they can agree on.


El

 

[Simon@NTS]

i will go with what sponners said about resetting the ecu by dissconnecting the battery

 

[HermaN]

IIRC, there is an idle adjustment screw on the throttle body, might have accidentally moved it while it was off being cleaned? Use EvoScan to lock the stepper motor into position, then adjust the screw until it is idling at 850 RPM, then re-enable the stepper. This is how you set the base idle.

EDIT: In EvoScan under "Actuators" it is at the bottom of the list and called "Speed Adj. Screw Mode", this is used to lock/unlock the stepper. If you don't do this it will keep trying to adjust the idle as you adjust the screw.

 

[toad660]

cheers for that El , just carn't seem to get my head round that all i have done is clean it out, i have reset the TPS and the base idle spot on with evoscan disconnected the battery for a hour and it just goes back to the fast idle at 1200rpm. i am starting to think that fast idle valve isn't working rightand isn't closing when the coolant in the throttle body as warmed up.........not going to give up .lol

 

[HermaN]

No wait, just saw you said when the stepper is locked it drops to 850....odd!

 

[toad660]

cheers for that HermaN, i will give that ago in the morning..cheers

 

[HermaN]

If you lock the stepper and it drops to 850, then the base idle has been properly set. However, the ECU will use the stepper to increase revs when cold to stop the engine dying, and as a nice side effect helps it warm up quicker. If the car tried to idle at 850 RPM when cold it would stall.

I know you never touched it, but if the thermostat was gone, then the ECU will not realise the engine is up to temp and keep the revs up, as if it was cold. Dodgy thermostat possibly??

 

[toad660]

yep as soon as i press actuator on evo scan it drops straight down to 850rpm and it spot on until i come out of it and its straight back to 1200rpm

 

[HermaN]

You posted at the same time as me. As per my above post, possibly the thermostat??

 

[toad660]

i see where u are coming from , looking on the web over the last week i have found out that there is a fast idle valve in the throttle body (dont know where) and it works in conjunction with the engine coolant, the valve is made out of wax / plastic and works the same as a thermostat , when the coolant warms up it closers the air way dropping back down to 850rpm. My problem is if this is true and the engine is warm and i use evoscan it drops straight down to 850rpm when i press actuate to set the base idle??????????

 

[HermaN]

My problem is if this is true and the engine is warm and i use evoscan it drops straight down to 850rpm when i press actuate to set the base idle??????????

Yes, because the ECU uses the stepper to increase idle speed when cold, when you activate the actuator you lock the stepper, so the idle drops, because the stepper is not longer adjusting the idle.

Sounds like it's related to the thermostat or that fast idle valve and coolant temps.

 

[ElDopesta]

What happens if you take the car for a short hard spin???

Does it drop down to 850 temporarily???

Cold Start is usually around the 1500 mark and above so it can't be down to the Thermostat, although it should not be ruled out just yet.

Have you tried to reposition the Idle Adjustment Screw???

Do the Revolutions drop down to 850 when you disconnect the MAF Plug???


El

 

[HermaN]

Cold Start is usually around the 1500 mark and above so it can't be down to the Thermostat, although it should not be ruled out just yet.

Yup, your right, cold start RPM is 1500, but if you look at the ROM you see that as the engine warms the ECU gradually uses less and less steps to bring the idle down to 850 RPM, it's not like an on/off switch, it's a gradual change, so if the thermostat or fast idle valve are partially stuck then it could cause it to idle at 1200 RPM.

 

[toad660]

I totally agree with u on this and i will check the thermostat to start with and if thats ok i really do think it can only be the fast idle valve, unless i am missing something.