VY Stalls under Deceleration only

[JasG]

Hi , I am new here great forum. I have a VY 03 V6 auto Ute, I am in need of help Please.
It runs great, Idles fine at lights never stalls otherwise, starts first turn. But once warmed up & only at speed(fine at lower speeds) Stalls as you decelerate say coming into a roundabout or down a hill. If i keep just a breath of throttle(drive double footed) to keep idle at say 1000rpm it fine, driving me nuts as if i let drop under that on decel it stalls & loose steering & brakes, put it in neutral hit key all good back in action. Its like the throttle body needed cleaning So did that, was a little dirty nothing major, pulled out Idle control solenoid cleaned as well. No difference, does have a slight vacuum sound especially when cold i don't recall being there before this started, i cannot find an air leak, no fault codes, no lights on, runs fine, idles everywhere else, but this is getting dangerous as if it stalls at wrong time as it doesn't always do it i could cause an accident. Its like i need to wind up idle just a bit, but i am aware you should not adjust the set screw. Been reading all the other comments with similar but worse issues & people advising changing coils, cam sensors, fuel pumps, ox sensors etc.. If it was any of that it would die all the time, it's more like you take your foot off throttle shuts and it starves for air & cuts out. I am thinking Idle control solenoid or Throttle position sensor or maybe air leak causing vacuum issue. Has anybody ever seen this? Really could do with some advice, Please. Thank you.

 

[PlenumBiscuit]

Cant give u a definite answer but once it heats up then it turns bad usually means crank angle sensor or dfi

But if like u say it just cuts out... or does it puff n spit n whinge and then stall

My initial thought would be to check fuel regulator if u go for a drive and after u can see the hose on the back of it is wet then its screwed

Else id lean to fuel pump relay or dirty fuel filter. Put injector cleaner through it or premium fuel. Swap pump relay with horn relay

Clean up battery terminals and get em on tight

Do u know how to test the coils?

Vaccum hoses u can get cheap from sprint auto park out the front and replace them all clamp them up tight. Theres about 4 all up to renew

At the back of driver side rocker theres a device where 2 vaccums hoses run to. Check if they're on tight and not split

Even check if oxygen sensors are in tight

All adds up

 

[JasG]

evBenji Thank you, I appreciate any help here & advice. I'll check what you suggested see what happens. Not 100% on testing of coils though. Or crank & cam sensors. As for your first question, hard to say really as I see the tach start to waiver up & down & battery light flickers then it either kicks back into life or cuts dead, no puff n spit n whinge so I am able to feather throttle most times as all I need to do is breath on it keeping around 900-1000rpm fine. Most times I don't actually realise its stoped until I see the battery light on & steering goes heavy as its coasting. Would not the crank or cam sensor cause a larger issue than this? As I never plays up other than say above 60kms on decel, I read somewhere today possibly speed sensor but that would cause other issues as well if failure. Or EGR valve blockage, dam such a tough one. I feel vacuum as I said I hear it louder when cold as worms up goes away. I'll test what you said & reply when done with outcome. Thanks again, very grateful.

 

[PlenumBiscuit]

Can u start it straight away after it stalls

U have 3 coils. Test coil one at a time... turn car off. Take the 2 leads off 1 coil only. Start car. Watch the coil if the lightning bolts join neatly... the coil is ok.... if the lightning bolts frizz around go buzzurk its fkd..... turn car off... put 2 leads back on it... then try the next coil same way

I would try a new tb sensor... see if u can get 1 cheap off a gumtree wreck unless brand new is cheap

All weird if not getting errors on the dash? Could be ecu playing up (last resort)

 

[JasG]

evBenji Thank you, legend mate, Yes starts straight away, no carrying on. When it happens I put into neutral hit key, back in action. Hard to do that all when your steering/turning, braking with a car up your clacker. Most times I can coast & do it, sometimes pull over. Hit key, on again. hard to turn a roundabout with no brakes & steering assist, nearly hit gutter a few times. Not good on P/Steering system, G/box etc as well as Autos don't like rolling at speed without converter turning. So this can cause many other issues the longer it continues.
My thoughts are throttle position sensor(computer going haywire when throttle returns to base) or idle control solenoid, or air leak as found rats have been living under manifold cover, they can do nasty things, see that before. Only seems to be one hose(oil breather) going into TB & a few small hoses(into cabin & FPR I think) & booster at rear of manifold, need to check more as fuel pressure vac line etc. Wondering if a manifold leak maybe.. as when I bought car invoice in glove box for manifold leak repair, but does not show any signs of ever being removed, as old oil & dirt says to me never been removed. I will see if I can find the procedure to test TPS etc, look more into air leak. Dam mystery that is weird & frustrating situation. Keep looking. Thanks for your help again. More heads are always better than one to bounce ideas off.

 

[statey1975]

Not sure of the V6 setup, but on my old LS1 the joiners in my PCV hose were all perished causing vaccuum leaks, wreaked havoc on my engine when taking the foot off the accelerator. fixed them up and all good!

 

[JasG]

statey1975 Hi Mate, Thank you, i have not had any time to look further so far, but yes good choice, i read somewhere similar issue can cause issues like this if vacuum leaking or especially if PCV is blocked up with gunk or in open position causes mixture issue confusing ECU. I only see a hose for breather coming off bottom of Throttle body S shaped going into manifold, it looks ok but by site only so far, i saw a diagram saying PCV valve lives between plenum & manifold dam i don't want to lift that area if i don't have to, hoses i hope/pray. I appreciate Any advice or direction. If anyone has diagrams or test procedures i'd be grateful also. Thanks again.

 

[greenacc]

Does it idle ok and accelerate smoothly? It doesn't sound like TPS to me if the only trouble you have is cutting out when you back off.

 

[JasG]

greenacc Thank you, Yes idles great, great smooth power, perfect otherwise than stalling on decel, its not doing it every time which is weird Never cold only once wormed up I believe when cold mixture is richer due to cold start etc, as worms up mixture leaner which brings me back to air leak. I can drive on freeway up down speed, stop start, but say come into roundabout or off ramp or at top of hill about to decline back off throttle at about 1000rpm tacho gives a little wave if it wavers down past say 500rpm out with the lights(well light come on as stalled), sometimes it will come back to life, I find if I just rest toe on throttle keeping at approx 900-1000rpm no issue. Driving me nuts trying to find issue. I have thought maybe throttle set screw may have a dent in centre ( Have seen this over years) from were it hits back to base, thought about tweak but they are set factory but over years it maybe worn a groove, as idle approx 800rpm in gear, maybe give it 1/4 of a 1/4 turn in see if it improves if I cant find a vacuum leak first, as if it was electrical it would cut out more regularly. Thanks for help.

 

[speedyvn]

Have you checked the operation of the brake booster? I know its odd and not the same car but a mates Subaru used to always do this, it ended up being the brake booster, doesn't take long to test its operation and whether its working or not.