Ls-V, obd1, eg hatch.

car idled fine last week (800-900). Within a 4 day span: the car gets tuned on dyno (smooth tune, no hiccups). After tune, noticed the car revving up to 3k on cold start-up (in the past didn't go as high). but goes down to reg idle.
Car also gets valve adjusted, re-thread of cam bolts that were stripped (maybe a little shavings flew in the head) & new oil, car idles fine, still revvs high on startup.

Car is raced (engine warm, new oil). car does fine. on 2nd pass, cars idles at 2,500 rshared_pm. for example, after i wrote this 1st post, went back to the car, started it and it revved to 5k directly, stayed there for 10s and then went down to 2-1,5k idle! Why does it rev that high on start-uP!?

1st FIX: Since then car will not go lower than 2,5k at idle.
With the help of other members, we were able to get the car to rev to 1500 on idle, still high, but driveable!.

However, on startup, car revs to 4,5-5k rshared_pm... (a little scary). then after a few minutes, as engine warms, car goes back to 1,500 idle.

Diagnostic that were done:
- NO vacuum leak
- changed IACV valve to OEM new one -> NO CHANGE IN IDLE
- TPS sensor within normal limits.

Sooooooo, does anyone have any idea?

The only thing i can think of is, for whatever reason, wiring?
I noticed that on the old and new IACV, if I unplug it, it does not seem to make a difference. Idle is the same... What could that mean?

anyone else have any thoughts? this is driving me crazy?!

UPDATE #1 - ran car from clearwater to tpa. When a/c on, engine idles to 1k. except when fan kicks on where it revs back to 1,5k for a couple of seconds. Left the car for about 30mn in the sun at parking lot, a/c was on when car shut was shut down. Started the car up (a/c on) and the car rev'ed up and down really quickly from 1,5 to 2,3 continously... until I shut off the a/c and idle dropped to 800-900! ( I was liek NICE It's back to normal!!) A/c still off, I go, idle is back to normal for a couple minutes. I put the a/c back on, idle still in normal range (around 1k). Turn a/c off at next light, idle is back to 1,5k... Dang! False hope!...

UPDATE #2 - Car is resting for the next 2 hours. Going to disconnect the battery. WIll see how car does when i head back home. well that didn't do crap!
Car still idles to 5k on cold startup and goes back to 1500 when warm.

 

Does it have a aftermarket throttlebody?and how's the pcv valve look?

 

Tb is oem stock. b16 head/ls bottom.
rangcrx - what do you mean by "how's the pcv valve look"? the one of the head is linked to the air intake. and the one on the Int Mani is plugged (black little plug on it).

 

Has to be a leak. No way around it. Check and see if something is holding your throttle body open, and then start looking for gasket leaks, caps missing off nipples, lines broken..its a big leak and you should be able to find it. Spray starter fluid around all the sealing surfaces and listen for idle changes.

The iacv cracked wide open couldn't make your car go to 5k, and right now its gotta be closed all the way trying to bring the idle down. Stick your fingers in the ports in the bore of the throttle body and see if it drops.

 

Well I wish it were that easy! And maybe we have missed something!
We sprayed carb cleaner over injectors, TB, IACV(because the lower bolt's thread is fucked, it's leaking a little, but not enough to create this problem), tps etc.. the whole top of the engine... NOTHING. No idle surge and nothing!

Did that, car revs dropped.

\
nothing. checked that too.

2 separate peeps have checked for leaks and nothing! IACV is set to factory setup (half way) right now we may try to set it lower and see if it responds... ruling out the IACV.

May try to use different ecu to see if anything changes...

Could bent valve be causing this?

 

If the revs dropped when you plugged the ports..then theres your first clue! Which one was it? The IACV or the FITV? a faulty fitv will cause this every time..they tend to fall apart inside.

And no one bad valve couldnt do this, but bad valve SEALS could.. plug the valve cover breather and see if it builds vacuum and drops the revs.

 

based on the research we i did on spare time, i was curious to rule out the fitv option... I was planning on replacing it with a another unit a friend has laying around to see if that may be the culprit.

Below are some "fun" videos (1mn when "somewhat cold engine". when the engine is really cold, the rev stays at 5k longer!)

 

Well if you plug the lower port and your idle drops to normal..problem solved.

 

did you take out your checkengine light bulb?

 

you don't see it in the vid because I already had turned the key, but it's there and working and not throwing any codes.