VT Gen 3 intermittent low idle

[Anglosaxon]

Sometimes when I pull up to a stop my engine sounds like its about to stall, it almost sounds like when you slow a manual right down with the brakes without pushing the clutch in (but its an auto), if i slip it into neutral the idle pops up to normal. It never actually stalls, and it only does it sometimes. Anyone come across anything like this before?

[m1lky]

Could be a small vacume leak?

If you think it's tranny related, I would just change the fluid. Nice and easy and it will be smoother for it

[Anglosaxon]

Yeah I'm thinking tranny, due to the fact I can actually hear the load come off the engine when I put the trans into neutral, I guess I was wondering if its a known symptom of something (serious or not) that im unfamiliar with, I'll service the trans hopefully that'll help.

Cheers.

[wassup353]

What's the best way to change the fluid without letting too much air sneak in?

[Munz]

don't worry about air getting in, I'd be more worried about spilling the fluid over the engine

[wassup353]

Because i topped up my fluid and got the same intermittent idle as discussed above. I'm guessing it was because too much air got in?

[Munz]

Try a PCM reset

PCM reset Proceduce

Motor at operationing temperature a MUST

1.Turn ignition ON
2. Model VT Remove PCM/BCM fuse number 4 which is F31 Note: for VX,VU ,V2 remove fuse F29 10amp Eng Cont/BCM

3.Wait 20 seconds for the Car to chime to you.
4. Turn ignition OFF.
5.Model VT Replace PCM/BCM fuse 4 which is F31 Note: for VX,VU ,V2 remove fuse F29 10amp Eng Cont/BCM
6. Proceed to the idle learn Procedure.

CLEARING THE DTCS
To clear a current diagnostic trouble code from the memory of the PCM, the PCM power feed must be disconnected
for at least ten (20) seconds, or the Tech 2 scan tool must be used. The battery power feed can be disconnected
by:
• Disconnecting the negative battery terminal
• Removing the Fuse F31 in the engine compartment fuse/relay panel.


CLEARING THE DTC HISTORY CODE
The Tech 2 scan tool is the only tool capable of clearing the DTC history code. Disconnecting the battery will not
erase DTC history. The Tech 2 scan tool sends a special message to the PCM to erase the DTCs.

IGNITION CYCLE DEFAULT
If the ignition is cycled (OFF and ON) 50 times without a particular fault resetting, that DTC will be cleared from the
PCM memory and the ignition cycle counter in the PCM will reset to zero. This is another way to clear any code, but not all, but might help you out.



Then follow the idle learn procedures

Idle Learn Procedure

Anytime the powertrain control module (PCM) or the battery is disconnected, the PCM loses power
by removing F31, or the PCM is reprogrammed, the PCMs learned idle position is lost.

Perform the following procedure in order to return the learned idle to the correct position:-

Automatic Transmission

1. Turn OFF the ignition.
2.Restore the PCM battery feed if removed, or replace fuse 4 which is F31.
3.Turn OFF the A/C controls.
4. Set the parking brake and block the drive wheels.
5.Start the engine.
6.Ensure that the engine coolant temperature is more than 80 Degrees.( Check in Mode Up button).
7.Shift the transmission into Drive.
8.Allow the engine to idle for 5 minutes.
9.Shift the transmission into Park.
10.Allow the engine to idle for 5 minutes.
11.Turn OFF the engine for 30 seconds.

Manual Transmission

1.Turn OFF the ignition
2.Restore the PCM battery feed if removed, or replace Fuse 4 which is F31.
3.Turn OFF the A/C controls.
4.Set the parking brake and block the drive wheels.
5.Place the transmission in Neutral.
6.Start the engine.
7.Ensure that the engine coolant temperature is more than 80 Degrees.( Check in Mode Up button).
8.Allow the engine to idle for 5 minutes.
9.Turn OFF the engine for 30 seconds.

[wassup353]

Tried the PCM reset and if anything it made things worse, nearly completely stalled at one point during the 5 minute idling period!

[Munz]

Did you try the idle learn procedure?

[Not_An_Abba_Fan]

Faulty TPS or coolant temp sensor.

[wassup353]

Yep tried the idle learn procedure as well straight afterwards like the guide says.

I'm going to reset the sensors first to see if that changes anything.

This idle problem literally happened the second after i added some more transmission fluid to the car. I don't know how but it seems that the tranny fluid was the cause?

Idles the same when the clutch is in and when it is out.

Ideas??

[kangavxss]

Sometimes when I pull up to a stop my engine sounds like its about to stall, it almost sounds like when you slow a manual right down with the brakes without pushing the clutch in (but its an auto), if i slip it into neutral the idle pops up to normal. It never actually stalls, and it only does it sometimes. Anyone come across anything like this before?

I had the same thing happen a few weeks ago - as i pulled up to a stop the revs would drop to about 200-300 and almost stall so i got my tuner to adjust the fuel trims and it
fixed it straight away.....

[Munz]

How clean is your throttle body/IAC?

I'm more leaning towards a vacuum hose, pretty sure behind the manifold it splits into 2 hoses, check there