MAF Problem - High Idle

[lidorik]

Hi everyone,

The problem: high idle (1800-2000 RPM)
Car: Silvia S15 Spec-R (Manual)


Modes:
Nistune ecu Type 4
Greddy bov type R (without recycling)
Z32 MAF
HKS Intercooler


What i have checked:
1. TPS on idle 0.5v
2. MAF on idle ~1.6v (increases when i put on pedal)
3. MAF (engine off) - 0.45v
4. AFR i set to ~ 13.5 - 14.0

5. No vacuum leaks (Why? read 5.1)

5.1 First test: So.. i was thinking the problem was dirty Idle Sensor (on Intake manifold), i get it from manifold and cleaned with spec. Spray, yes it was really dirty. I put it on intake again and start engine without MAF and without pipe on intake manifold. The idle was pretty good - 800-850 rpm. I turned pipe on intake manifold, connect wires on MAF and start engine - High idle again...

Second Test: I changed BOV with Stock recycling, correct AFR but again High Idle

Third Test: I disconeccted MAF and connected OEM MAF - again High Idle

And last test: I disconeccted MAF, corrected AFR and IDLE is about 550-600 rpm, not very stable but not bad. the engine not targeted on 2000 rpm



The Map is full Stock, i changed only K Constant for AFR

I tried to change: TTP min, TTP max, Target idle but nothing helps it...


It's fact that when ECU looks that MAF is connected something strong is going on... but Maf voltage is normal

I checkec it with Z32 maf and stock maf, no matter...

What else i must check? What can i do?

Any ideas?

 

[Auss15]

Has the MAP been tuned to run the Z32 AFM ?

 

[lidorik]

Yes, Nistune has special functions "Change Maf", but there is no difference, idle is 2k rpm again

But, with stock Maf as i wrote rpm is the same - 2000 rpm

 

[Auss15]

Seems strange because the resolution between the 2 AFM's is different...

 

[lidorik]

Seems strange because the resolution between the 2 AFM's is different...

I know, i saw VQ map has changed, MAF voltage is normal (both), after VQ map changes it needs to adjust K Constant for normal AFR

I tried to adjust VQ map manually, tried high and low values at working sectors but it's a fact that VQ map is not reason.


Now i must check IACV valve, i cleaned but i have doubt if its solenoid works

 

[Clarkey]

When did this problem start, after what changes?

What happens if you put it in set base idle mode?

Is your MAF/filter shielded from the radiator fan? I ask because I had crazy problems with the idling after my engine swap and it was because of air blowing off the fan into the MAF.

 

[lidorik]

It starts after:

1. I changed BOV (relocated near MAF), STOCK bov was Recycling but this last one - GREDDY TYPE R is not
2. Changed pipe from turbo to intercooler pipe (needed for BOV) - old pipe was stock as i know 2", and new pipes are 2.5"
3. Installed Z32 MAF (with correct wiring) with new K&N air filter

BOV is not working now, cause vacuum is not enough for low boost levels
BOV air direction target is AIR filter (as i wrote bov not working)

The old bov is on it's place but without vacuum line, i left it for testing..

So after this changes, before i start engine i connect nistune to car and i changed VQ MAP (with nistune function "CHANGE MAF")

I started engine and BOOM - here we go, after this i have problems

Interesting fact: when i was thinking that the problem comes with incorrect maps, i was trying to upload base map, sometimes ENGINE WAS WORKING GOOD (with nice 800 rpm), but when i turn ignition off (Burn map changes or upload map) and start engine again the problem comes again


After that i made this tests:

1. working with stock MAF - FAIL
2. working with stock BOV - fail
3. working with stock MAF and BOV - fail
4. turn off MAF - not bad (idle 800 - 900)


New tests i'm thinking:
1. Check IACV valve - if solenoid works under electric
2. if first check fails, make car as stock as it was in old times when it was working (with maf, bov, pipes and etc.) and upload base map again

If problems gone - the reason is hardware

 

[lidorik]

SOLVED!

it was IACV problem

i replaced it and everything works fine

 

[subzero]

off topic but is the nistune software easily got ? ive a nistune ecu in my 180 and would like a nose through it .

 

[lidorik]

off topic but is the nistune software easily got ? ive a nistune ecu in my 180 and would like a nose through it .

You must buy software from nistune.com, soft is easy to use, you can download demo version of nistune from nistune.com