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S90 76MM TB Issues?

Got everything fitted back together and fired it up. Idle was around 1600 but then as the car warmed up the dreaded hunting idle between 1500-2k plus came in to it. Not sure where to go from here. TPS was calibrated to 0.49 closed and reading 4.6 WOT on a halfords multimeter.
 
Whats the idle learn?

I was going to clean it but the screws were going to round so I just left it. I messaged the fella I bought it off to confirm there were definitely no issues before removal and he said it was perfect. Took his word as no real reason to lie weeks down the line.
 
Turn on from cold, make sure all election loads are off and hold at 3k fast idle until fan kicks in (thermostat opens/engine reaches usual temp) then let idle naturally for 5-10 mins or something, will tell you in the book. Just lets the ecu re-learn the idle characteristics.

Unless the chap cleaned it I suspect there will still have been siht in there that has congealed and might be sticking the mechanism. If it's the same style TB as an EP3 you can cheat and clean with some carb cleaner and blue roll. Spray a bit down either side and wipe it out. Worked a treat for me as I couldn't get the screws out either, although I had a low idle, not hunting. Other thing to try is a bit of red-line driving to clear it out, although if the carbon and stuff has gone solid that won't work. (Anyone remember what the slang for fixing it by driving is?)


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I pulled the TB back off. Only took a few minutes. Of course as I suspected....the bolts have rung holding the IACV in place. I want to do it right so going to drill the bolts out and use the 2 bolts from the S90 TB which came off effortlessly of course!

Im assuming since these are so tight that they have never been removed and will hopefully be dirty in there. If its clean then I guess i'm back to square one. Then theres always the possibility of using the IACV from the S90 but it could have been blanked off for a reason? Torture but hope to sort it tonight.
 
Got the IACV off and it was fairly gunked up put it back on spotless and still having the same issue. Going to switch the sensors on the IACVs while its on the car and see if this resolves the issue.

If it doesnt, my last option is to re use the s90 IACV amd sensor along with blanking plate and hope this solves the issue. As there was no hunting issues with the s90 on whatsoever.
 
Did you do the learn? I know it sounds silly to ask but you haven't mentioned doing it.

I'd start looking at sensors and for leaks, and I'm not convinced you can totally blank off the IACV on the OEM TB because the butterfly valve closes completely, but someone who knows K20's better will have to confirm or deny that either way.

There's 10's of threads on here about EP3's and so on with idle hunting, so I'd also have a good look around them if you get the chance. The first suggestion is always the IACV but I'm sure there'll be more if you dig down.
 
Sorry Nick yes I did try that. Im now left in a position where....
A) I attach the TB with IACV not blanked and the revs hunt between 1500-2500
B) I blank off the IACV like it was on the S90 by the previous owner and the idle is around 500 and trying to stall until it warms up a little bit.

I'm wondering if the air aasist valve is the next place to look as this was blanked off by a bolt but removing the bolt makes no difference which I found odd .

I have cleaned the IACV as well as swapped sensors from the other one I have here. The readings from the TPS are now bang on. Not really sure where to go from here to be honest.
 
The assist valve is just to get more air in so it warms up faster, wouldn't cause hunting issues at operating temp. Idle at 500 is very low, the ep3 shakes like absolute stink at less than 550. There must be something that's causing it to go skwey. I'd try A) and drive it a few miles to see what happens.


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CTR_Nick said:
The assist valve is just to get more air in so it warms up faster, wouldn't cause hunting issues at operating temp. Idle at 500 is very low, the ep3 shakes like absolute stink at less than 550. There must be something that's causing it to go skwey. I'd try A) and drive it a few miles to see what happens.


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Thanks Nick. Thats what I am going to do. I will refit the TB as it was with the IACV. Check all hoses after the throttle body again. I did see in a thread that someones idle was hunting due to a coolant leak (low level) and I noticed my top hose had a minor split with a bit of coolant leaking out. I believe the IACV does have a small hose that flows coolant so wondering if this would be connected.

Generally I don't keep cars too long but i'm treating this motor as an investment and over time will be tidying up any little things it needs to leave it almost perfect.
 
PROBLEM SORTED!

Feel a bit silly but the issue was the IACV sticking. The video guide I watched showing how to clean it gave no mention to removing the sensor and cleaning there as well as making sure the cylinder rotates freely. Turned out it wouldnt rotate at all despite looking clean. After a good bit of cleaning and soaking in carb cleaner it was free as a bird.

Carried out the idle learn and cold start now seems to be around 1500 and steadying about 1k when warm.

Thanks for all input in sorting this!
 
No worries man, you're welcome. Glad to hear it was an easy fix!! Always good to check a couple of guides make sure you're not missing something.

When I get around to buying some new coolant hoses and bolts I need to do my IACV properly. Hoses were seized and starting to split so I did it in situ. When you drilled it did you drill completely and use a stud extractor or did you just crack the heads and use what's was left to grip and unscrew?


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Ended up getting vice grips on the culprit and got it loose that way so didn't need to drill in the end.

I've something similar to do next week myself. Bought some type 2 coolant and will be draining the system then replacing the top coolant hose which is slightly split at the same time will have to find a how to.
 
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