slight hesitation on takeoff?

[HULK_I6T]

I have an au series 3 forte with 158000km..

car drives great. But noticed sometimes from a standing start, if you give it a decent shove to takeoff it has a slight hesitation and then then goes. Like a slight miss and then shes away. Not always but sometimes?

ive noticed that if it sits in drive for a bit (like at the lights) and then more than half throttle it just hesitates and then goes.

when driving or kicking down a gear etc never does it. If in neutral and just rev it all of a sudden its fine. Never does it in any other scenario and not always..

car has plenty 98 fuel in it, recently run fuel injector cleaner, new air filter, new fuel filter, new spark plugs, cleaned throttle body, new cat converter and exhaust. Car idles smoothly.

Im thinking a dodgy lead or coil? Or fuel pump?

But never does it at high revs or any other scenario. Only standing start when sitting in drive for a while at low revs and then give it a bit of throttle all of a sudden.

any ideas?? Im being picky but i like my cars perfect.

[XC50077]

My EF11 did this after about 2-3 minutes from cold and new Oxy sensor fixed it. Au3 O2 sensor is due for replacement at 150,000km.

[Maka]

Hi there, make sure your intake manifold bolts are tight & also check each cylinder for spark quality, it may be down half a cylinder due to yellow spark.

Check if your transmission is a little low on fluid. If you can get hold of a ecu scanner, do a scan & see what comes up. Also check your o2 sensor like xc50077 suggested. Good luck!

cheers, Maka

[Sox]

Originally Posted by Maka

Hi there, make sure your intake manifold bolts are tight

This was the problem on my brothers AU a couple years back, vacuum leak.
We had to change the intake gasket.

[Sox]

Originally Posted by Sox

This was the problem on my brothers AU a couple years back, vacuum leak.
We had to change the intake gasket.

I still have my money on this...

[HULK_I6T]

Originally Posted by Sox

This was the problem on my brothers AU a couple years back, vacuum leak.
We had to change the intake gasket.

no funny idle at all and intake manifold bolts on tight.

seems to just hessitate under load, on hard takeoffs just a slight hesitation and she is away. when cruising its fine. idle is perfect

Also now noticed if you are cruising and hit the throttle it hessitates and then goes. I think its getting progressively worse.

now ordered new leads and coil pack. try them out when they arrive. Ive heard changing the coil pack is a pain in the bum.

[Sox]

Originally Posted by f6_benito

no funny idle at all and intake manifold bolts on tight.

seems to just hessitate under load, on hard takeoffs just a slight hesitation and she is away. when cruising its fine. idle is perfect

Also now noticed if you are cruising and hit the throttle it hessitates and then goes. I think its getting progressively worse.

now ordered new leads and coil pack. try them out when they arrive. Ive heard changing the coil pack is a pain in the bum.

Sounds exactly how my brothers AU went.

[HULK_I6T]

Any benefit in pulling out the fuel pump and attempting to clean the fuel sock?

Anything to watch out for? Should I just get a new fuel pump?

I already have a coil and leads coming from ebay..

The issues seems to be getting worse on a daily basis, coincidence that my fuel levels are less and less each day also? I'll give it some new fuel tomorrow and see if it effects condition

[Lajon]

I have the exact same problem on ours..was soo bad one day that we actually stalled in the middle of an intersection!

[HULK_I6T]

Ive ordered an 02 sensor.. ill report back if its the fix.

[HULK_I6T]

O2 sensor arrived so will fit up tonight.

Update is that it seems to have a. Initial hesitation on heavy changes in throttle. Light throttle car is ok but give it a stab off the line there is hesitation and the. She's off.. Or going around a corner and then punching the throttle there is hesitation?

But revving flat stick (after initial hesitation) right to redline the cars goes beautifully.

[HULK_I6T]

Changed o2 sensor but problem remains.

[mcfly94]

mmm, maybe coilpack, dirty fuel filter, fuel sock, fouled up plugs, hi resistance in leads. Lots to check, change fuel filter, fuel sock, and plugs, there all about $20/30 each, then id probably look at the fuel pump or coilpack

[Lajon]

what and where is the fuel sock located?

[Maka]

Originally Posted by Lajon

what and where is the fuel sock located?

The fuel sock is a filter/strainer located on the fuel pump inlet port.

cheers, Maka

[Grippy]

Is it better or worse depending on the amount of fuel in the tank? Sounds like the same thing I had with my old XR6 VCT. It was generally worse with a lighter load of fuel on board and taking off after making a turn it would surge. It was the fuel sock.

[mcfly94]

My fuel pump actually died, so I replaced it with a gss342, problem fixed

[mcfly94]

yeah I don't think the fuel sock can be cleaned, new fuel pump is is about $150 for a walbro and 3 hours labour, standard is $60 and about 2 hours labour

[Maka]

I would check your spark before looking at the fuel pump. Get a spare plug & assistant, remove a lead, fit old plug & earth out plug on tappet cover. Start car & without zapping yourself, observe colour of spark, blue - good yellow - bad, repeat for all spark plugs. Wont cost nothing good luck!

cheers, Maka

[HULK_I6T]

UPDATE

fitted new fuel pump (+ new fuel sock) and fuel filter and full tank fo fuel.

still has hesitation problem...grrrr!!!! fuel sock pretty black and looked abit gummed up so prob good i changed it..

Anyway coil and leads should arrive today or tomorrow so I will replace them over the long weekend and see if it fixes it..

AU is supposed to be super reliable!!

[Sox]

Originally Posted by f6_benito

UPDATE

fitted new fuel pump (+ new fuel sock) and fuel filter and full tank fo fuel.

still has hesitation problem...grrrr!!!! fuel sock pretty black and looked abit gummed up so prob good i changed it..

Anyway coil and leads should arrive today or tomorrow so I will replace them over the long weekend and see if it fixes it..

AU is supposed to be super reliable!!

They are. It hasn't stopped.

Change the manifold gasket and all will be fine.

[JC]

Originally Posted by Sox

They are. It hasn't stopped.

Change the manifold gasket and all will be fine.

I love the way he/she has tried everything except the thing that will actually fix it. It doesn't have to have a bad idle for the intake gasket to be at fault.

We had similar issues on our territory, and intake gasket fixed that too, and it idled ad ran perfectly, except for the slight miss on hard acceleration.

[HULK_I6T]

Originally Posted by JC

I love the way he/she has tried everything except the thing that will actually fix it. It doesn't have to have a bad idle for the intake gasket to be at fault.

We had similar issues on our territory, and intake gasket fixed that too, and it idled ad ran perfectly, except for the slight miss on hard acceleration.

This will be next if the coil/ leads don't fix..

Cold the car is ok, but as soon as it heats up a bit seems worse. Wouldn't intake manifold gasket leak more when cold? Seal up when hot as it expands? Also seems to be getting worse almost daily. A few weeks ago all good and gradual decline.. Intake manifold bolts are tight.

[Grippy]

Good stuff Hulk.

[mcfly94]

mm might replace mine when I do a service, mine has a little idle issue normally not noticeable! did you use a genuine vdo?

[HULK_I6T]

Just bought an ebay cheapie.. $60 delivered

Works fine..

Not that hard to change, just need a 7mm socket and long extensions, 3 bolts

Need to also remove airbox to get your arm under there and air intake from throttle body.

It's an hours job max.

I went on a good drive the other day. piece of mind with a new coil. If hate for it to fail a few hundred km from home

Years back on an el falcon I had one just go cold on me whilst driving. Just conked out under load..

[Maka]

Hey f6, does your au feel stronger down low since replacing the coil or did it fix just the hesitation?

cheers, Maka

[HULK_I6T]

Originally Posted by Maka

Hey f6, does your au feel stronger down low since replacing the coil or did it fix just the hesitation?

cheers, Maka

Na feels the same.. Just fixed the hesitation

[Maka]

Originally Posted by f6_benito

Na feels the same.. Just fixed the hesitation

Ah ok, thats what i thought too. Thanks for clearing that up!

cheers, Maka