shudder when slowing..?

[ECOJET]

Hi all... hopefully a simple answer for this one!
In my AU Monty as of late i've noticed when braking and coming to a stop the car will sometimes shudder like it's going to stall (hasn't stalled as of yet)
anyone what generally this be due to, or can it be a plethora of possibilities?

[Lukeyson]

do you feel the shuddering in the brake peddle ? ifso warped disc's maybe?
but you do indicate you think it may be about to stall .....

[Stattic]

its ABS lol... were you braking hard or in the wet?

[JC]

What have brakes got to do with the engine speed?

I'd check/clean the IAC/ISC valve, and also the power steering switch. mine shudders too, almost to stalling point, and I'm fairly certain mine is the power steering switch - which reminds me,; I should ring up for a new one!!

[aye you]

i had a similar problem and it turn out to be a dying PCM after cleaning the ISC, resetting the ECU the whole lot

[JMO]

The PCM is the ECU isn't it?

[Stattic]

Originally Posted by JC

What have brakes got to do with the engine speed?

because when abs kicks in it feels like the whole front is shuddering.. its just a suggestion...

[AUbigfoot]

It is on lpg? Mine does this sometimes but I'm not sure if it's an lpg problem or not (I have only noticed the shuddering on lpg mainly)

[JC]

Got my power steering switch thing from AutoPro for $37 - hope it fixes my shudder!

[GK]

Originally Posted by JC

Got my power steering switch thing from AutoPro for $37 - hope it fixes my shudder!

Do a "how to" on the install.

GK

[ECOJET]

Originally Posted by JC

What have brakes got to do with the engine speed?

I'd check/clean the IAC/ISC valve, and also the power steering switch. mine shudders too, almost to stalling point, and I'm fairly certain mine is the power steering switch - which reminds me,; I should ring up for a new one!!

yeah i should have probably clarified this is all engine, brakes work fine no shuddering there...
She has never stalled but came close. IAC valve makes a lot of sense, ill try the quick clean out of that tomorrow.. p/s switch is interesting too, if the iac makes no difference then that'll be the next area of focus.
Where abouts is the switch located? near the rack or... ?

[Swordsman88]

THe suggestions made by JC are probably a good place to start. Also consider auto transmission. If the auto is failing to engage first fast enough (remember btr box has very tall ratios) then the rpm will drop too low in second gear and you risk stalling it. It isnt' all that common but it can happen, even if the shift is jsut delayed a bit. Often dirty/burnt fluid or other auto issues (which we all know can happen on high km btr boxes).

Edit: torque converter lock up issues also cause this sensation....if it doesn't unlock fast enough its basically a manual in too high a gear with the clutch out....

[JC]

Originally Posted by ECOJET

yeah i should have probably clarified this is all engine, brakes work fine no shuddering there...
She has never stalled but came close. IAC valve makes a lot of sense, ill try the quick clean out of that tomorrow.. p/s switch is interesting too, if the iac makes no difference then that'll be the next area of focus.
Where abouts is the switch located? near the rack or... ?

The switch is a PITA to replace - yes it is down on the rack near where the steering column/intermediate shaft join the rack. I did mine today, and while it seemed to make a difference initially, it really is no better at idle. It doesn't shudder when you turn the wheel though at idle, so that is fixed. I just cleaned my ISC as well, so I'll see how that goes tomorrow.

[JC]

Originally Posted by GK

Do a "how to" on the install.

GK

It's not hard tod do, just need a "special" 15mm spanner (By special, I mean shortened 2 inches, and the edges of the spanner head flattened out to get enough spanner on the nut).

[smally289]

Originally Posted by Swordsman88

Edit: torque converter lock up issues also cause this sensation....if it doesn't unlock fast enough its basically a manual in too high a gear with the clutch out....

This is what Im betting is the problem. Have seen it many times on these vehicles.
Not all that hard to diagnose. Try slowing to a stop before the convertor has had a chance to lock - it should be ok. Then go drive until it does lock, then stop. If it shudders / stalls then you have a lock up problem.

[JC]

Well, ISC is clean, and it works, but car still shudders/nearly stalls; that is until I adjusted the idle screw. The white paint used to mark it from factory was cracked, and a bit over half a turn saw the pattern in the cracked paint line back up, so i think thismay just have worked it's way loose over the 180,000+ km. i've used a 4mm nut to act as a lock nut now, so we'll see how that goes tomorrow. Idle is now more 750 to 800 instead of 650 to 700, which just sounds a bit better and is as per specs in the haynes manual.

[JC]

Idling is good - when coming to a stop, it drops down to about 650 and then stabilises at about 750 (previously was dropping as low as 500 rpm, and on the odd occasion, it was stalling).

[GK]

Originally Posted by JC

Idling is good - when coming to a stop, it drops down to about 650 and then stabilises at about 750 (previously was dropping as low as 500 rpm, and on the odd occasion, it was stalling).

Good news!

GK

[vbomber]

A little bit off topic, what is the idle rpm for an AU I6

[JC]

Originally Posted by vbomber

A little bit off topic, what is the idle rpm for an AU I6

Between 700 and 800 according to the haynes manual. I set mine closer to 800 in P and N, so it ends up at around 650 to 700 in D.

[vbomber]

Originally Posted by JC

Between 700 and 800 according to the haynes manual. I set mine closer to 800 in P and N, so it ends up at around 650 to 700 in D.

thanks for that, I will double check tomorrow night but I believe mine sits at 580-600rpm in D :

[JMO]

That is where the problem lies with mine. It is a touch under 600rpm in drive but the idle screw has never been touched so it must be a sensor or such that connects to the ISC that is playing up. I've tried almost all of them. Finding my problem seems to be harder than finding Bin Laden...

[JC]

Originally Posted by JMO

That is where the problem lies with mine. It is a touch under 600rpm in drive but the idle screw has never been touched so it must be a sensor or such that connects to the ISC that is playing up. I've tried almost all of them. Finding my problem seems to be harder than finding Bin Laden...

My advice is to turn the idle screw half a turn in and see how you go.