VN IAC Valve Winaldl Test

[88GreenVN]

OK looking at the data I got from the Winaldl test I've done on the 2 VN V6's the base data is about 7 units apart

The 88 wagon sits at 31 and the 89 sedan sits at 24 - both with spikes.

The cars were driven over the same test loop and this is the only real change between the 2 I could find.

Anyone know why this would be?

Added the V8 run plus the 88 V6 wagon Greenfoam tune run in Jan 2008

[88GreenVN]

Here is the coolant temp readings from the 3 VN cars. 2 runs in 2006 (88 V6 & 91 V8)

The 88 wagon twice - 1 with the greenfoam tune in it Jan 2008 The 89 sedan Sat night

[Cheap6]

Different engines.

Different amount of wear, manifold vacuum leakage, oil viscosity, state of tune etc.

Seems normal to me.

[88GreenVN]

The second chart (first post) was from the same car with a standard tune for the yellow line and a Greenfoam tune with the light green line - they are miles apart. Does the memcal tune have anything at all to do with this or is it just the IAC valve doing something different now.

[Cheap6]

Sorry, looking at yellow and red lines, ~31 and ~24, which would be OK. Ask greenfoam ?

[88GreenVN]

Sorry - 2 stories there - 1 between the wagon and the sedan and the other is the 2 tunes between the wagon. My bad.

Greenfoam it is....

[vnv8driver]

You cant trust the ALDL data all the time mate, with my vq which ad a bit of wear & tear, after a full set of new sensors, gaskets, servicing etc, the iac still showed up the same as yours and you could not pinpoint the problem. As mentioned before it comes down to sheer wear & tear.

[88GreenVN]

You cant trust the ALDL ata all the time mate, with my vq which ad a bit of wear & tear, after a full set of new sensors, gaskets, servicing etc, the iac still showed up the same as yours and you could not inpoint the problem. As mentioned before it comes down to sheer wear & tear.

What dose this IAC valve do - what controls it?

[vnv8driver]

Manifold vacuum controls the 'angle' of the iac valve which then communicates with the ecu to maintain a steady/smooth idle, thats why if its gunked up it wont allow your motor to idle properly, i couldnt underdstand even after a NEW manifold gasket, rebuilt injectors, & every single sensor replaced the problem still existed, maybe it was a partially burnt out valve or god knows what but without ripping the thing to pieces there was no way i could determine the cause of it all, i also suspected it was an electrical woe in the wiring which is also a bit hard to diagnose without removing the whole setup (with limited sparky knoledge)...thats why it was easier for me to sell it for a cheap price to my mate : )

[88GreenVN]

So a burn valve or vaccum leak will mess with the IAC valve. The car came with a major miss in the engine. Some injector cleaner has made most of it go away. Greenfoam gave it some power.

But a minor miss still remains.

Car has plenty of poke - spins up the new 215's if you give it a bit of stick. I may just scab a IAC valve from the wreckers on Friday and wack that in and do another dest drive.

[vnv8driver]

also get the throttle body gasket replaced as its bound to break as soon as you remove the t/b, grab some garden hose and use it as a stethescope to listen for minor air leaks whole the motors running although that test isnt exactly the best around sand can be false.

Get a cheapo compression test kit from supercheap if you dont already have one and check compression in each cylinder for consitency, then remove the brake booster hose coming out of the manifold and stick the compression test kit in the end of it (so the test kit can monitor vaccum while the motors running) switch the motor on and look for rapid jumps (low pressure) on the gauge. The kit will have instructions for each test and is relitively easy to do.

[88GreenVN]

also get the throttle body gasket replaced as its bound to break as soon as you remove the t/b, grab some garden hose and use it as a stethescope to listen for minor air leaks whole the motors running although that test isnt exactly the best around sand can be false.

Get a cheapo compression test kit from supercheap if you dont already have one and check compression in each cylinder for consitency, then remove the brake booster hose coming out of the manifold and stick the compression test kit in the end of it (so the test kit can monitor vaccum while the motors running) switch the motor on and look for rapid jumps (low pressure) on the gauge. The kit will have instructions for each test and is relitively easy to do.

With my hearing - no hope of finding a leak.

Compesion test is next on the to do list - maybe Friday if my brother passes on welding up new A frame on his trailer.

I think the car got new plugs on April - should check that too.

[vnv8driver]

what other programs are you running? i found that efi live v4 and tuner pro rt are the best out of them all

[88GreenVN]

what other programs are you running? i found that efi live v4 and tuner pro rt are the best out of them all

Just the Winaldl program. I could not get EFI Live to work and got annoyed with it.

Fig I have data from several runs over the same test loop so kept with the Winaldl program. I want to understand how it all relates to the health of the car and what to look for so I'll keep studying the data and making graphs

[vnv8driver]

ask greenfoam for the files you need for a vn ecu to be recognised in efi live & tuner pro, you need to open the program and load the special file which supports your car/ecu. My laptop is off getting fixed as it just died under warranty so i dont have any links or files at the moment.

[Cheap6]

What dose this IAC valve do - what controls it?

The Idle Air Control valve controls how much air is allowed to pass around the throttle plate giving the ECM some control over engine speed. If you have the throttle body off and the IAC valve out you can see the passage the air passes through.

The valve is on a screw thread wound in and out by an electric motor controlled by the ECM, thus closing or opening the valve, depending on which way the motor turns. The motor is a 'stepper' motor (with two sets of windings) which basically means that it moves through discrete angles (steps) each time power is applied to it.

The numbers you are seeing in the WinALDL logs are the number of 'steps' the ECM has commanded the IAC to open. The range is 0-255 i.e. 256 steps. Somewhere between 5 and 40 steps is usual at idle, accessories off but the value is not critical.

To reset the position to a 'known' value, the IAC is commanded at least (possibly more - I don't know) the full 256 steps open when the throttle is held open for long enough (during normal driving).

The number of 'steps' used to maintain idle speed with/without A/C and in/out of gear (auto only) load on the engine is learned by the ECM and used as the initial value when the car returns to idle. Then it adjusts the motor position to maintain the desired idle speed.

The actual IAC position may not match the position the ECM thinks that it is in. This might happen if the IAC motor sticks and doesn't move when the command pulse is given. This is why sometimes a stalling condition occurs if the IAC +/or throttle body (bypass port) are dirty.

Re. high steps values. One thing to check might be the base idle speed. It shouldn't need to be altered but often it gets messed around with, usually out of ignorance.

This is adjusted by altering the postion of the throttle stop screw. It should be covered by a little green plastic cap (to prevent tampering) but if not, it's suspect.

If the cap is present, leave it. If it's not and the throttle body/IAC is clean and engine tune is good (prerequisites), run the engine up to operating temperature and with all accessories off (including the cooling fan - wait 'til it cycles so) and with the air duct removed, block the port to the IAC valve with a finger. It will be hot so if you don't have asbestos fingers, use a cloth.

An alternative is to force the IAC closed by creating a vacuum leak (disconnect a vacuum hose) to artificially raise the idle speed, letting the ECM try to correct it and then disconnecting the IAC motor connector. You can't be totally sure that the valve is closed though, so I use the finger.

The engine speed should drop to, depending on the series, ~450-550rpm. If it's not in that range, adjust the throttle stop screw until it is. The engine will be very nearly stalling. This is correct. With everything back together, let the car idle in/out of gear A/C on/off to relearn the IAC motor position.

Otherwise, greenfoam may have changed something in the mapping, so we're back to asking him.

If swapping in a used IAC valve, check the profile on the end of the valve (pintle) carefully. There were a couple of different shapes used.

[88GreenVN]

I just printed that ^^^^ - Wow thanks for that info cheap6. I think the engine is idling just a little high when you pull up to lights and hold the brake - it just seems to want to creap forward - but only a little and has just a little harshness throgh the body. New engine mounts in last week fixed most of the harshness - but not when stopped at the lights.

Looks like I'm getting grubby tonight.

Thanks again