VN V6 Idle speed?

[IvegotaCommy]

Anyone know what RPM and how to set the idle speed of a 3800 V6 Auto? Mine is running about 1100 which seems to me to be too fast.

[Cheap6]

Yes, 1100rpm is too fast.

No you can't adjust the idle speed - idle speed is controlled via an air bypass port around the throttle plate, the size of which is determined by an ECM controlled "plug" (the IAC motor).

You can adjust the base idle speed which is the result of the minimum throttle opening with the IAC port blocked (or IAC motor fully extended).

You shouldn't try to adjust the base idle speed without good reason but someone else may have tried to do so. If there is no green plastic tamper evident cap over the throttle plate stop screw, post back and I will explain how to adjust/check the base idle speed. (There is already a thread on here but I may as well explain it again as try to find it.)

Your high idle is likely to be due to another problem, a vacuum leak somewhere. Likely sources are broken/split/disconnected hoses or perhaps an inlet manifold gasket leaking.

[immortality]

howz about we try the easy things first. what does the inside of the throttle body (TB) look like, i bet it's covered in black gunk. disconnect the battery first. then remove the TB from the car and clean thoroughly with a can of carb cleaner. best if you can remove the idle air control valve (or IAC) and clean out all the passages to this also. make sure you don't soak the TPS in carb cleaner.

once all is clean, re install and make sure all vacuum lines/hoses are connected. the reason we disconnected the battery first is because we want to reset the ecu, which normally means disconnecting the ecu for at least 10secs. you've already done this. reconnect battery and rev engine to 3000rpm for 10-15seconds. this resets the IAC. let throttle go and return to idle. intially it will be idling high, this is normal, then the ecu will adjust the idle speed using the IAC. when it's settled properly it should be about 800rpm


if it's still idleing high then either you have a faulty IAC or the base idle is set to high

[Cheap6]

OK, if the idle is inconsistent, try the TB clean. I prefer to avoid the carb. cleaner or at least be very careful with it. It tends to wash the lubricant out of the throttle spindle bushes/bearings, which allows the bushes or bearings to wear - another potential source for a vacuum leak. A kero soaked cloth works well, with particular attention to the edges of the throttle plate and the tip of the IAC motor pintle.

Yes, a stuck/dead IAC can cause a high idle.

The 3000 rpm reset procedure isn't necessary though, the ECM will (re)learn basic IAC motor settings if let idle, when the engine is at operating temp., A/C on and off, in P and D.

[Emackulation]

Yeah, do what Immortality said, you could have some build up which is wedging the butterfly open.

[dazzavp]

hey instead of makin another threat may aswell add to this one. my vp v6 idols like ****. drops n raises from 700 to bout 900 everytime im sitting at the traffic lights..what could this be from?? i have removed the bellmouth but seems the erattic idol started a few months after removing it. sometimes when i change into neutral or park it drops as low as 500 then back to imbetween 700 n 900...hmmmm

[Bz Kn33z]

yeah sounds like the IAC Idle Air Control there is a How To to clean the TB, just get some carby cleaner and spray it into the TB when car is on and into the IAC the holes in the TB Take the Black pipe off to get to it.

[immortality]

i'd also be checking for a vacuum leak. did you damage any gaskets when you removed the bellmouth?

[IvegotaCommy]

Well, now I know. Been driving the commy around and it stopped on me twice. Each time the car went fine until I stopped and switched off the engine. Then it would not re-start. Waited around for 15-20 minutes until the car cooled right down then it re-started OK. Again ran fine until I stopped. Then would not restart. Eventually drove home and motor idled OK. Switched off then immediately tried to re-start. No start.
Mechanic thought it might be the fuel pump. But I can not see how. Why would it run and idle OK then not re-start. If there was a problem with the pump it would cut out when driving.
I think this might be a long standing problem which I have inherited from the previous owners. That's why the thermostat had been butchered and put back in. The car will only re-start when cold.
What do you think it might be? I would like to find and fix it as I need the car to be reliable.

[immortality]

when you say it doesn't start, does it turn over on the starter but doesn't fire or it doesn't crank at all? if it doesn't crank, can you hear the starter making a click (ing) noise? i'd suggest you also change your fuel pump and starter relays and see if that does anything

edit: the tacho not reading correctly is a common problem. when it's idling and reading 11-1200rpm give the dash a few firm taps above tacho, it should drop to a more accurate reading. it's most likely a dry joint onthe back that need re-soldering. fairly common, normally the fuel level guage doesn't read correct either, same problem etc

[Cheap6]

OK, this is likely related to the thermostat replacement? If so, perhaps coolant temp. sensor or ECM? You can check the temp. sensor easily with an ammeter (a $10 cheapie multimeter is OK) across the terminals:

110C = 110 ohms
100C = 190 ohms
90C = 250 ohms
70C = 450 ohms

So about 130 ohms would be operating temp.

ECM is a bit harder without a means to determine what it is actually "seeing". Do you have a diagnostic cable (or are willing to make one) and access to a laptop with a DB9 232 port? Actually, you could use a PC, just not be able to travel further than the power cable allows . It would be OK to use idling in a driveway/garage if you have no other option.

Any fault codes? There are two circuits used by the ECM to process the coolant temp. signal, one being switched in only above a particular temp. reading (which I can't recall). Sometimes the circuit fails to switch in (ECM fault) = dodgy temp. input to ECM. It may not set a code if the temp. is within range though, it will just read something like -10C when it is actually above 70C . => Too much fuel can cause a hard start.

It is also possible that in attempting to set the base idle with the thermostat absent, it is now too low, so the engine stalls. The hard restart is a bit odd though.

[IvegotaCommy]

Have been talking about this problem and someone pointed out that cars are designed so that when the motor does not run the fuel pump shuts down so that in the event of a crash and/or fire it will not 'feed' the fire.
Reading the book it seems that in the VN the fuel pump relay only runs for 2 seconds and then switches off. Only when the engine starts and runs does the oil pressure switch turn on the pump again.
So my idea of the fuel pump had to be good because it ran ok with the engine running might be a tad wrong . It might well be the fuel pump relay that has a problem and it is purely coincidence that I replaced the thermostat. Another thought is that maybe low oil pressure for whatever reason is causing the pressure switch to be slow to operate when cranking. However this most likely would need a pressure leak in the fuel feed to be feasible?
Replacing the fuel pump relay is the direction I will be going in trying to fix this. Thank you everyone for your comments.

[Cheap6]

If the fuel pump relay fails, the car will just be slow to start because the oil pressure switch has to close ie. there has to be oil pressure present, before the fuel pump will operate continuously. It's not that the relay "hands over" operation of the fuel pump to the oil pressure switch, they operate in parallel and if either is working and the engine running, the fuel pump will be powered. The ECM provides the fuel shut off by not powering the fuel pump relay if it doesn't detect that the engine is running. The oil pressure switch is powered off the ignition switch.

To check the over fuelling hypothesis, associated with a dud coolant temp. reading: will the car start in "clear flood mode", ie. with the accelerator pedal pushed to the floor will the engine fire?

If you think it may be the fuel pump (I don'think so either but..) hit the centre of the fuel tank with the palm of your hand when the car won't start and try again to start the car.

It could also be a crank sensor or CS wiring; the 3X signal is only used on starting and can fail when it is hot.

[IvegotaCommy]

I have set up a small light, connected to the diagnostic connector. This shows me when voltage is being supplied to the fuel pump. Operation is clear, the light comes on when the ign. sw. is on, stays on for about two seconds then goes off. Once the engine starts, the light comes on and stays on until the engine is stopped. Even see the oil switch pulsating on/off when cranking.
Yesterday, the car again would not start. Operation of the light as above. So I can rule out all problems with the relay and oil light switch. I now think it must be the fuel pump. I think the commutator is dirty and it stops on the dirty spot. What I should be able to do is hear the pump running. But every time this happens I am in very noisy surroundings so I can hear nothing from the pump.
Anyone know how much for a new pump?

[Cheap6]

The gasket and in tank filter are ~$25 (new) and a pump and sender another $25 (used) . (Maybe new would be better but $$ ??? from me).

Maybe try bridging (shorting) the switched side of the fuel pump relay to confirm that the pump doesn't operate when the car stops ie. remove the fuel pump relay and join the 87 and 30 female (car) terminals. The pump should then operate with the ignition on.

[vnv6s]

found one on ebay for a decent price
vn fuel pump - eBay VN, VP, VR, VS, Holden, Car Parts, Cars, Bikes, Boats. (end time 03-Jan-08 12:45:35 AEDST)

[Just_a_stocker]

yes clean the TB, clean the IAC (or replace only if needed $80.00), jiggle and push the tip back to < 28 mm (if it is the oldr adjustable style) from the base.
replace yr TB gasket and reset the ecu.
be carful and use a decent carb cleaner, see how it goes as a preliminary.
If it doesn't help you may have to look further.
I have onwned a Vn an VP and 1000 rpm idle is fine.


cheers

[IvegotaCommy]

Today, I thought I would try something else. I thought it important that I be certain that it was either fuel or spark. So I drove until the car was good and hot, found myself a shady spot and shut down the motor. Tried to restart and nothing. So I connected a strobe flash timing light to a handy sparkplug lead and cranked it over. No spark. Nothing. Nada. Zilch.
As well, I could clearly hear the fuel pump run. So nothing wrong with fuel at all. Problem is no spark.
Cheap6, you said something about the CS giving problems. What did you mean?

[lilredwagon]

it's behind the harmonic balancer (crank pulley) and is known to cause problems when beginning to fail - hot start issues etc...
another thread on this site mentions pouring cold water in behind the balancer to cool it down as a quick check, but I haven't had to try this myself...?

[Just_a_stocker]

Yes about a bucket full enough to cool the Crank sensor and revive it for a bit, probably enough for a restart.

Its an easy test so if your having troubles diagnosing the prob, give that a try next time it stalls and if it starts you can bet its your CAS.

[Cheap6]

Today, I thought I would try something else. I thought it important that I be certain that it was either fuel or spark. So I drove until the car was good and hot, found myself a shady spot and shut down the motor. Tried to restart and nothing. So I connected a strobe flash timing light to a handy sparkplug lead and cranked it over. No spark. Nothing. Nada. Zilch.
As well, I could clearly hear the fuel pump run. So nothing wrong with fuel at all. Problem is no spark.
Cheap6, you said something about the CS giving problems. What did you mean?

On a V6, there are really two crank angle sensors in the single package, one that is used to measure both crank position and crank speed - with 18 "slots" = on/off switches (18X signal) and one used to determine which cylinder should be firing - with 3 "slots" (3X signal).

The 3X sensor has slots of 1, 2 and 3 times the width of the 18X slots, each corresponding to (or close to) TDC on a pair of cylinders; the end of a compression stroke on one, the end of an exhaust stroke on the other. The number of times the 18X signal occurs per 3X signal is used by the DFI to determine which coil to fire. Once that has been determined on initial start, the 3X signal is not used again until the engine stops. Here, the DFI is performing the function that the distributor cap and rotor button perform in an engine fitted with a distributor.

If the 3X sensor/signal is only failing when hot, the engine will continue to run but will not restart (because the DFI can't determine which coil to fire) if/when it stops. I guess it could also be the circuitry in the DFI that performs this function too, but I can't recall seeing that before.

To test the CAS:

There are 4 wires to the CAS; one 12V (power) via the DFI module, one earth via the DFI mod. and the two signal wires which earth signal voltage sources from the DFI mod..

The wires are:

white/black = power supply to sensors; ~12V

grey/red = earth for sensors

dark blue/yellow = 18X sensor signal earth

light blue/white = 3X sensor signal earth

Two options for testing:

The CAS wire can be awkard to get to so to make it easier, pick up a CAS harness connector, with some of each of the wires attached, from a wrecker. Unplug the car CAS and plug the test connector in instead. Breaking the retaining tab off the test connector makes it easier to get on and off. With some of the insulation stripped from the ends of the wires, it's now easy to connect the appropriate wires to the battery and an earth. Use a test light connected to ~12V and each of the sensor signal wires to check the operation of the sensors (the test light alternates on and then off) as the crank is rotated by hand.

The second option is to check the sensor operation at the DFI module connector, using the car/DFI mod. power and earth. Undo the wiring harness to the DFI mod. (7mm head bolt) and connect jumper wires between the power supply and earth wires from the DFI mod. to the disconnected DFI mod. harness connector. This can be tricky because the male pins are quite close together and it's easy to touch two at once but it does check the wiring between the CAS and the DFI mod. as well as the CAS. You could also source a DFI harness connector from the wrecker, as for the CAS connector, to use as the jumper wires. (I haven't felt it necessary because I have the CAS connector and an ohmeter to check the wires for an open circuit or short to earth). Again use a test light between either an external (on car) ~12V source or the 18X and 3X signal pins on the DFI, and the wires to the sensor signal earths. (The ignition needs to be on for this method to work).

[Cheap6]

Bump after adding CAS test methods.

[IvegotaCommy]

I went down to the local wrecker and he had a crank sensor so bought it. Problem though. Mine is automatic. How do you lock up the engine in order to remove the bolt from the harmonic damper? The book talks about some inspection cover on the flywheel which is removed to stop the flywheel from turning. But I can not find anything. Anyone have a pet method they would like to share?

[Cheap6]

How are your fabrication skills and how involved do you want to get . I use a tool I made which fits into the slots in the front of the balancer (early balancers don't have the slots though) and rests on the chassis rail. Actually, I made two, because the slots in one non-genuine balancer weren't slots but holes . Some 25mm square RHS ~5mm wall plus two 8mm shank bolts, nuts and a drill (although I welded mine) would probably do it. (I know a picture would help). Or, you may be able to borrow something similar from a workshop.

I understand that some people have used an old accessory drive belt wrapped around the pulleys - maybe search on here (sorry if that is too vague).

To access the ring gear, you would have to drop the starter motor or remove the "beaming brace" - the cast metal cover that extends under the rear of the engine sump. That usually means dropping the steering rack.

You can undo the balancer bolt by cranking the engine while holding the bolt using a breaker bar with a pipe over the handle for leverage (disconnect the CAS first - you don't want the engine to start) but doing it back up again may be difficult - usually that is done using an air gun.

Generally, much attention is paid to undoing the bolt and not much to doing it back up. The bolt has a pretty high torque spec., beyond most torque wrenches. The trick is to mark the bolt and balancer before you undo the bolt, loosen it off and retorque to a value within the range of the torque wrench, then note the angular distance between the marks. When refitting the bolt tighten it to the value used before with the torque wrench, plus a bit to properly seat the balancer, then back it off and tighten it once again with the torque wrench and add the angular distance noted before. The bolt will then be at the same tension it was before being removed.

You also need to remove the old sealant from the crank keyway groove and from inside the balancer and replace it with new sealant - I prefer Permatex Ultra-Blue - or there will be an oil leak. Replacing the oil seal in the front cover, which has to be lubed w'engine oil befor putting the balancer back on too, is also a good idea (although I don't always) because disturbing it can cause it to leak even if it isn't now.

You could, of course, just pay a workshop to do the job .

I take it that you did find the CAS to be the problem?

[IvegotaCommy]

There is no doubt about you guys. Especially you Cheap6. You were right on target with diagnosing the CAS as the problem.

I eventually went back to the guy I had bought the sensor from. Figured he got the 'new' one off, he should be able to get it back on to mine. He used a rattle gun to do it. I have driven around to try it out and it always starts, no matter how hot it gets. So seems to be cured.

After reading your comments re sealing, however, I am not so sure I went to the right mechanic. I suspect he never cleaned anything and never used sealer. I doubt he used a torque wrench either. Since getting it back, there has been a large vibration from the motor, too. I think I read in the book about the sensor needs to be set for clearances when installing. Maybe he didn't do that either. I think I am going to have to find a real mechanic to do it all properly. Might go to the GMH agent, they should be able to do the job properly.

At least the failing when hot problem seems to be cured, so thank heaven for something. Thank you, all.