I have noticed lately that when I accelerate hard, shifting from 2 to 3 the car will stall ever so slightly before the revs increase with the throttle down in third.

This only happens immediately after going from 2 to 3 when I let the clutch out and have the gas full down. The car is a manual with 30k.

Any ideas on what this is? At first I thought I may be timing the change ever so slightly off, but I can reproduce it and its only from 2 to 3. I would think if its a clutch wearing issue it would happen in all gears.

Any help is much appreciated.

 

First, you probably shouldn't let the clutch out with the gas fully down as you say. Lift off the gas with clutch in to let the RPMs drop slightly then feed the gas back only after the clutch has fully engaged. A properly timed upshift should not cause the RPMs to bog down after you pull out the clutch. Letting the clutch out on full power as you describe instead of rev-matching will wear your clutch out more quickly.

Second, the sign of a slipping clutch is not a slight stalling as you describe. In fact, it is quite the opposite—you press down on the gas and the RPMs rise without the normally corresponding thrust in forward speed.

Apologies if this sounds rather academic.

 

Karl-Appreciate the response but perhaps I was not clear enough. I am not letting the clutch out with the gas fully down! It is after I have disengaged the clutch then press down the gas pedal full throttle that this is occurs, and it is only when going into third.

 

Best check is 4 gear low speed floor it and look for rpm rise with out gaining ground

 

+1 , this is the proper test of a slipping clutch. Get into a higher gear that is close to 1:1 then quickly push down the accelerator and see if the clutch slips. Te reason you have to go into higher gears is you need a much higher load to test the clutches grip limitation.

 

Took the car out and while going slow put it in fourth and quickly pushed down the accelerator.....no slip at all. Speed increased slowly as did the RPMs.

Not sure what it could be?

 

Not the clutch then
Have you tried cleaning the throttle body?

 

You could be running super rich, if so you could actually cause the engine in theory to stall momentarily as the fuel floodgates open. Could also be a sign of dirty fuel Injectors, try running 1-2 full cans of seafood in the gas tank to clean up the entire fuel system, this should help it greatly if it is intact the proper cause of your hesitation.

Best way to know is get e car dynoed with air fuel ratios and see how rich she is running. If you are below 10:1 I could see that possibly causing issues

 

Thanks Mikey and 007-will try both.

*EDIT*-007, I sent you my dynos after the last addition with the CATs....much leaner and holding steady around 12. Did you mean Seafoam?

 

Haha, yes SeaFoam, stupid apple autocorrect. I did not even pickup on that. Although 1-2 cans of seafood could cleans your own system (but that's a different story).

 

Hope ur not thinking about running seafoam through the engine(please stay away from this method untill you know what is the fault), get the car scanned and see if the misfire corrections are learned first..this is a dealer only thing
You could be misfiring at that concern and not even know it due to the corrections not being learnt..

Are the misfire corrections learnt??

 

No, as I stated previously before very specifically, you run it through the gas tank so it goes through the whole fuel system.

 

Do you think you might be experiencing the rev-limiter taking control? The 2-3 shift takes slightly longer than the 1-2 shift, and perhaps it is coming into play. Have you noticed your shift indicator when experiencing the problem?

 

Don-you may be on to something as it was only the 2-3 shift at the limit. I shift off the sound/RPM and am not looking at the shift indicator. But In 2+ years I have hit the rev limiter 2 or 3 times and it's very apparent.

irish- The engine runs brilliant, I don't think its a misfire. Had it scanned recently and all was fine. What do you mean by are the misfire corrections learnt?

 

On the Aston motors, the PCM wants to know it's exact settings for the 36-1...On the crank is a trigger wheels called the 36-1, there is 35 even spread teeth and 1 large spread tooth..aka 36-1 trigger wheel. This reading is compared with the cam sensor, which results into your injectors and spark plugs firing at the right time. The vehicle will run in something like open loop for firing it's injectors and spark plugs untill the drive cycle for the misfire corrections is learnt..which is not a really good thing...

If the misfire corrections are not learnt, a drive cycled road test for the 36-1 relarn has to be performed..untill this is performed..shifting on ASM won't be as nice, the misfire monitoring will not work at all..so you could fry a catalyst due to misfiring and not even get a MIL light due to the corrections not being learnt.

I had a auto trans DB9 recently, guy was complaing that on the highway, when he was about to pass and applied hard load(increased speed to pass), the engine would start cutting out on him...but there was no check engine light at all..

I scanned the car and got no codes at all, I noticed when I datalogged that the 36-1 misfire corrections had not been learnt..performed the road test to relearn the corrections and right away I got a MIL flagging code P0304 on secondary..turned to be a faulty secondary winding in the #4 coil on secondary bank..

Not saying this is your concern, but a lot of Aston I get don't have them learnt, and once I get them learnt the MIL light comes on to inform me whats going on..

There are a lot of dealerships that doin't perform the 36-1 nor bother with it due to teh time it takes them to complete a road test..sometimes takes me 1 hour due to traffic in my work area!!

The biggest thing I see on V8V's with out the misfire corrections being learnt is stalling, client is driving and presses clutch in while coasting..engine stalls because it has not learnt the relation of the engine speed(36-1) and the road speed(wheel sped sensors)..client thinks something is wrong, yet it's just the misfire corrections that had been lost from a dead battery and needed to be relearnt.

I've also had a V8V manual that had the clutch replaced by another garage(corner place) along with the flywheel..engine ran great but when shifting through gearing engine wanted to die if the rpms was near 1000-1500 once shift was complete...ended up being the misfire corrections needed to be reset and relearned due to the new flywheel that was installed(trigger wheels for 36-1 is on the flywheel)..relearnt everything and car ran perfect..

Again, not stating this is your concern, but I would check this step first before investing money and time into things that might not be the solution..get the car scanned to make sure the Misfire Corrections are learnt..get a print out from the dealer to be 100%..then go from there as you wish..

If they are learnt then you can at least know the software in the PCM is not causing your concern..