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[hatchboy]

type r head, gsr block.
Have had a hunting idle issue that i need to resolve, Starting goofing off with it today finally, when engine is cold it idle's fine, when it is warmed up it hunts from 900-1400 ish. I unplugged the IACV and the engine stalled which tells me the IACV is in fact working, I have taken it out and cleaned it previously.
Started looking underneath and at schematics in the service manual, turns out the passenger side bung on the IACV connects below the throttle body, that is connected fine.

Looked at the other side of the IACV on the drivers side bung, the hose is coming off and plugged with a bolt. I realize that it is supposed to be connected to the crossover pipe on the block but my crossover pipe on the block does not have a bung to connect the hose.

Could this be the causing factor of my surging idle? Considering coolant is coming in to the IACV but not being let out? Or is the line from the crossover pipe actually the feed line?

[DSMR]

Do you have a FITV on your Throttle body? If so, take off the pipe on the throttle body. While it is idling, block off the bottom port with your thumb (IIRC it is the bottom port). If the idle goes down like it should, your issue is your FITV needs to be cleaned/adjusted.

[hatchboy]

Do you have a FITV on your Throttle body? If so, take off the pipe on the throttle body. While it is idling, block off the bottom port with your thumb (IIRC it is the bottom port). If the idle goes down like it should, your issue is your FITV needs to be cleaned/adjusted.

No FITV on it as it is a 98 type r head/manifold. Only hole is at the 9'oclock position going to iacv i assume.

[JaredKaragen]

Stock manifold... Good.

Stock unmolested throttlebody?

[hatchboy]

Stock manifold... Good.

Stock unmolested throttlebody?

Yes, completely stock. I am pretty sure the IACV is working correctly, with it unplugged i can set base idle around 550 with very very minimal fluctuation. With it plugged in it hunts constantly 800-1400.
I am starting to lean towards a vacuum leak somewhere, not to try and diagnose it.

I had it running last night, sprayed carb/choke cleaner over pretty much every vacuum line etc and did not observe and type of rpm change.
Then i hooked up my hand pump vacuum tool, and realized i was a retard because i was not going to be able to pull any vacuum with it at all.

Next step to finding a vacuum leak?

[snm95ls]

The coolant hoses are there to keep the valve from freezing up during cold conditions.

If you plugged the IACV hole iwth your finer and the engine stalled, I highly doubt you have a vacuum leak.  The fact that you sprayed flammable cleaner around the manifold and saw no appreciable change in RPM also leads me to believe there is no vacuum leak as well.

Are you running a non-stock calibration?  If so, what EMS platform?

I would check your minimum air rate.  Bring the RPM up by opening the throttle plate, plug the IACV opening with your finger, and slowing close the throttle plate so that the engine will continue to idle.  I should be about 450-550 RPM if I recall correctly.

I think there is a spec for it in the FSM.

[JaredKaragen]

If the ecu is stock;  it must be vacuum leak, sticking iacv, or low vacuum reading seen by PCM; possibly incorrect TPS reading in ecu also.

Check your sensor output through a DLC of some sort;  if using an ems it needs to be tuned properly...


It's soooo much easier to do this kind of diagnosis in person...

[snm95ls]

If the ecu is stock;  it must be vacuum leak, sticking iacv, or low vacuum reading seen by PCM; possibly incorrect TPS reading in ecu also.

Check your sensor output through a DLC of some sort;  if using an ems it needs to be tuned properly...


It's soooo much easier to do this kind of diagnosis in person...

This.

[hatchboy]

If the ecu is stock;  it must be vacuum leak, sticking iacv, or low vacuum reading seen by PCM; possibly incorrect TPS reading in ecu also.

Check your sensor output through a DLC of some sort;  if using an ems it needs to be tuned properly...


It's soooo much easier to do this kind of diagnosis in person...

This.

P28 w/crome pro tuned by Dave Lee
It has done this since day one of this new engine, with the limited time myself and dave had while street tuning two years ago, we couldn't figure out why it was fluctuating.

[crttaz]

FITV not fully closed?

Brake booster vac leak?

[hatchboy]

FITV not fully closed?

Brake booster vac leak?

No FITV on this manifold/Throttle Body.
Brake Booster is a valid possibility, I didn't spray around it too much. If that was leaking would it affect my braking at all?

I am going to give it a once over again and see if its got a vacuum leak, if not, it has to be the tune..

[JaredKaragen]

If the ecu is stock;  it must be vacuum leak, sticking iacv, or low vacuum reading seen by PCM; possibly incorrect TPS reading in ecu also.

Check your sensor output through a DLC of some sort;  if using an ems it needs to be tuned properly...


It's soooo much easier to do this kind of diagnosis in person...

This.

P28 w/crome pro tuned by Dave Lee
It has done this since day one of this new engine, with the limited time myself and dave had while street tuning two years ago, we couldn't figure out why it was fluctuating.

This explains it.

100% tune related is my guess if it's not a sticking iacv.

I have had some cars be a royal PITA with idle; especially ones that like to dip down very low after a pull.

Most of the time I can smooth it out and get it right.  The rest of the time I was able to get it out on a retune later down the road.

I've been able to get stage3+ cams to idle smooth and return to a smooth idle at roughly 900rpm on 1k+ injectors...   It takes a LOT of fancy timing/fuel table modification, but it can be done...  It's just tricky; like the idle on some vehicles.

[hatchboy]

If the ecu is stock;  it must be vacuum leak, sticking iacv, or low vacuum reading seen by PCM; possibly incorrect TPS reading in ecu also.

Check your sensor output through a DLC of some sort;  if using an ems it needs to be tuned properly...


It's soooo much easier to do this kind of diagnosis in person...

This.

P28 w/crome pro tuned by Dave Lee
It has done this since day one of this new engine, with the limited time myself and dave had while street tuning two years ago, we couldn't figure out why it was fluctuating.

This explains it.

100% tune related is my guess if it's not a sticking iacv.

I have had some cars be a royal PITA with idle; especially ones that like to dip down very low after a pull.

Most of the time I can smooth it out and get it right.  The rest of the time I was able to get it out on a retune later down the road.

I've been able to get stage3+ cams to idle smooth and return to a smooth idle at roughly 900rpm on 1k+ injectors...   It takes a LOT of fancy timing/fuel table modification, but it can be done...  It's just tricky; like the idle on some vehicles.

That is what i am leavning towards as well, I am going to pull off the IACV one more time and soak it in cleaner, if that doesn't clear it up, im going to have to see if i can get ahold of leed to come do his work again.
I can't find any vacuum leaks whatsoever, the only other thing it POSSIBLY? could be, is that i have the GM 3 bar coming off the vac manifold, should it has its on source directly from the IM?

[92CXyD]

If the ecu is stock;  it must be vacuum leak, sticking iacv, or low vacuum reading seen by PCM; possibly incorrect TPS reading in ecu also.

Check your sensor output through a DLC of some sort;  if using an ems it needs to be tuned properly...


It's soooo much easier to do this kind of diagnosis in person...

This.

P28 w/crome pro tuned by Dave Lee
It has done this since day one of this new engine, with the limited time myself and dave had while street tuning two years ago, we couldn't figure out why it was fluctuating.

This explains it.

100% tune related is my guess if it's not a sticking iacv.

I have had some cars be a royal PITA with idle; especially ones that like to dip down very low after a pull.

Most of the time I can smooth it out and get it right.  The rest of the time I was able to get it out on a retune later down the road.

I've been able to get stage3+ cams to idle smooth and return to a smooth idle at roughly 900rpm on 1k+ injectors...   It takes a LOT of fancy timing/fuel table modification, but it can be done...  It's just tricky; like the idle on some vehicles.

That is what i am leavning towards as well, I am going to pull off the IACV one more time and soak it in cleaner, if that doesn't clear it up, im going to have to see if i can get ahold of leed to come do his work again.
I can't find any vacuum leaks whatsoever, the only other thing it POSSIBLY? could be, is that i have the GM 3 bar coming off the vac manifold, should it has its on source directly from the IM?

YES 

[JaredKaragen]

It's always ideal to have the map on its own dedicated vacuum source with the largest connection hose possible....   

Moving it I highly suggest a retune as well.

[hatchboy]

possible bubble in coolant line at temp switch. It's happened to me a few times on a b16.
it's worth checking it out.

I have drained coolant three times since i built this latest engine, i would think that a bubble in the same spot is unlikely yes?

[JaredKaragen]

I doubt it.

If you ever doubt bleeding cooling systems look into the "airlift". Worth it's weight in gold.

It puts the cooling system in a vacuum, then using that vacuum you can assess potential leaks; and finally use it to draw coolant into the system.  It will fill all crevices and leave little if no air bubbles in the system.  No bleeding, no burping, no stress or chances of issues.  Fill and drive away without sweating anything.

[hatchboy]

I doubt it.

If you ever doubt bleeding cooling systems look into the "airlift". Worth it's weight in gold.

It puts the cooling system in a vacuum, then using that vacuum you can assess potential leaks; and finally use it to draw coolant into the system.  It will fill all crevices and leave little if no air bubbles in the system.  No bleeding, no burping, no stress or chances of issues.  Fill and drive away without sweating anything.

Well when I filled it this last time, i had the front of the car on jack stands and burped it with squeezing the hoses etc. Today when i get home from work i am going to re-route the vacuum hose from the map straight to the manifold instead of on the very end of the vac manifold and see if it makes a difference.

[hatchboy]

i would think that a bubble in the same spot is unlikely yes?

not unlikely at all, the bleed off screw is the high point of the system so air bubbles go there.
Having the front of the car up on jack stands will throw off the high point. You are supposed to bleed the coolant system on level ground.

michael,
Last time i checked, My car didn't have a bleed screw.......
98 jdm itr head.
I think they stopped the bleed screw stuff in the higher years for some reason.

[hatchboy]

Hey don't act like I should know if it has one or not. I don't buy any hype r stuff.

however I still say double check it again can't hurt.

What wire harness are you using?

Custom harness that i built. And no, it does not have a bleed screw. I think its all 96+ motors or something that don't have bleed screws, not positive on the year, but almost positive that the higher years dont have one.

[hatchboy]

[hatchboy]

could the ecu be looking for a FITV?
Have you replaced the IACV yet?

no and no i havn't replaced it, just taken it off and cleaned it a couple times.

[Tim]

Edit:

My IACV does have coolant lines, nevermind.

[JaredKaragen]

Ya the cooling lines are just for very cold temps...  Not much of a worry.

[hatchboy]

Ya the cooling lines are just for very cold temps...  Not much of a worry.

I am almost 100% positive its the tune. With myself and dave not having a lot of time on it, and precision 1000cc's i suspect it just needs to be massaged out a little more.\

I took the IACV off again, cleaned it again, checked it with 12v source and the plunger is operating normally. I moved the MAP to its own vacuum source with a big hose, no change in idle.
Warmed it up, unplugged IACV and set base idle, although it was still fluctuating at 500rpm slightly, so it haz to be the tune.

Everyone agree?

[92CXyD]

Ya the cooling lines are just for very cold temps...  Not much of a worry.

I am almost 100% positive its the tune. With myself and dave not having a lot of time on it, and precision 1000cc's i suspect it just needs to be massaged out a little more.\

I took the IACV off again, cleaned it again, checked it with 12v source and the plunger is operating normally. I moved the MAP to its own vacuum source with a big hose, no change in idle.
Warmed it up, unplugged IACV and set base idle, although it was still fluctuating at 500rpm slightly, so it haz to be the tune.

Everyone agree?

Agreed 

[hatchboy]

Ya the cooling lines are just for very cold temps...  Not much of a worry.

I am almost 100% positive its the tune. With myself and dave not having a lot of time on it, and precision 1000cc's i suspect it just needs to be massaged out a little more.\

I took the IACV off again, cleaned it again, checked it with 12v source and the plunger is operating normally. I moved the MAP to its own vacuum source with a big hose, no change in idle.
Warmed it up, unplugged IACV and set base idle, although it was still fluctuating at 500rpm slightly, so it haz to be the tune.

Everyone agree?

Agreed 

Also. TPS in closed position reads .51  Close enough yes?

[92CXyD]

Ya the cooling lines are just for very cold temps...  Not much of a worry.

I am almost 100% positive its the tune. With myself and dave not having a lot of time on it, and precision 1000cc's i suspect it just needs to be massaged out a little more.\

I took the IACV off again, cleaned it again, checked it with 12v source and the plunger is operating normally. I moved the MAP to its own vacuum source with a big hose, no change in idle.
Warmed it up, unplugged IACV and set base idle, although it was still fluctuating at 500rpm slightly, so it haz to be the tune.

Everyone agree?

Agreed 

Also. TPS in closed position reads .51  Close enough yes?

I use my datalog screen to adjust my TPS to be near zero -1% to 2%.

If ya reading like 10% on datalog , or the TPS has a dead spot when moving the throttle real slow, could cause some problems with idle. 

[hatchboy]

Ya the cooling lines are just for very cold temps...  Not much of a worry.

I am almost 100% positive its the tune. With myself and dave not having a lot of time on it, and precision 1000cc's i suspect it just needs to be massaged out a little more.\

I took the IACV off again, cleaned it again, checked it with 12v source and the plunger is operating normally. I moved the MAP to its own vacuum source with a big hose, no change in idle.
Warmed it up, unplugged IACV and set base idle, although it was still fluctuating at 500rpm slightly, so it haz to be the tune.

Everyone agree?

Agreed 

Also. TPS in closed position reads .51  Close enough yes?

I use my datalog screen to adjust my TPS to be near zero -1% to 2%.

If ya reading like 10% on datalog , or the TPS has a dead spot when moving the throttle real slow, could cause some problems with idle. 

No dead spots, everything said .49 to .50 is dead on, I am .51 and thats how it was when i was NA and it ran like a raped ape.

[HiProfile]

i have the GM 3 bar

I found your problem, that and precision 1000's are that precise at idle. Watch the datalog for AFR's and vacuum, I'm going to guess both start swinging unusually when you unplug the IACV port. By swinging I mean they read wrong since the MAP isn't giving the correct value, and the tune at idle isn't that great.