Stutter / hesitation under heavy acceleration

[850 2.5 10v]

When putting my foot down and getting the revs up I get a slight hesitation or stutter when changed to the next gear (not the gear change itself!!).

The car then recovers and all's well.

Only seems to happen under heavy acceleration which is not often but is a pain when changing down to pass a tractor on a B road....

Anyone any idea of what might be causing this?

Thanks All

[timbo_1975]

I would start with the plugs, leads, rotor arm and cap. When were these last changed?

The 2.5 10 is usually a willing worker, but blighted by overly high gearing..

Tim..

[mk3phill]

i had the same proble,. changed plugs/leads/cap n rotor arm still the same :(

[850 2.5 10v]

It's had:

Dizzy and Arm back in Sept 07

Plugs - 2 weeks ago (done by Volvo while reading a code)

Leads were done 3 years ago if I remember correctly - PFV ones.

It's had quite a bit spent over the years - mostly at Volvo.

Could a fuel pump be the issue not 'keeping up'?

It only happens under heavy acceleration and when changing gear - either up or down

PS: car is manual.

Other than that its a great car -HLM are just sorting my ABS should have module back today. (I have not been driving it since I removed the old one!!)

[timbo_1975]

Give the throttle body a clean, (remove it to do it properly) check for vac leaks, and that the MAP sensor hose isnt kinked, blocked, or rubbed through on the rad cowling..

You can of course check the fuel filter is recent too..

[850 2.5 10v]

Timbo thanks for your replies.

What is the MAP? I have heard of MAF no MAP - any pics as to where it is?

TB was cleaned by Volvo just last week as was the Throttle Position sensor and all working fine.

VAC pipes - are they the yellow ones with black ends that sit on the christmas tree under the plastic throttle cover?

[timbo_1975]

On the Fenix managed engines (the 10valvers) the map sensor is on the rad support bracket next to the fan relay and connected to the throttle body via a white hose with black rubber ends. There is NO MAF on this engine, only an air temp sensor in the maf position..

Check all the other vac hoses to the christmas tree, and the o-ring was replaced on the vac tree when the throttle body was removed.

There is also a connection to the manifold under the PAS pump at the other end with a rubber elbow that likes to split..

Tim..

[c70Portree]

id put money on it being the air flow meter, my c70 t5 man was doing that, felt like huge turbo lag? disconnected the air flow metre and problem solved, that was three months ago now and still have the airflow metre disconnected.

[850 2.5 10v]

On the Fenix managed engines (the 10valvers) the map sensor is on the rad support bracket next to the fan relay and connected to the throttle body via a white hose with black rubber ends. There is NO MAF on this engine, only an air temp sensor in the maf position..

Check all the other vac hoses to the christmas tree, and the o-ring was replaced on the vac tree when the throttle body was removed.

There is also a connection to the manifold under the PAS pump at the other end with a rubber elbow that likes to split..

Tim..


I had a look at a few of these hoses and some of the black ends did look a bit tired. I might try Rufe and see about costs for them...

Is it just a matter of pulling off the old and popping on the new ones?

- Nothing else special to action first?

cheers

[Niles]

MAP = Manifold Absolute Pressure

[mk3phill]

id put money on it being the air flow meter, my c70 t5 man was doing that, felt like huge turbo lag? disconnected the air flow metre and problem solved, that was three months ago now and still have the airflow metre disconnected.

they run a map sensor mate, there isnt a maf on this engine