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Author Topic: 2.5 V6 power and torque (lack of)  (Read 3113 times)

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mtbskills

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2.5 V6 power and torque (lack of)
« on: 10 February 2010, 09:45:48 »
Bit disappointed with performance for a big (ish) v6, mainly lack of low down torque

Seems very flat below 3000rpm, better above that.

Multirams are operating (visually while revving engine), slight blow on centre section of exhaust.

Usually drive a D5 diesel volvo, which has loads of low down torque, so am I expecting too much
or can anyone suggest what to check next ... cant afford to replace exhaust yet   :(

Thanks  :y
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djac

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Re: 2.5 V6 power and torque (lack of)
« Reply #1 on: 10 February 2010, 10:02:53 »
It might be just down to the differing characteristics of petrol and diesel engines.

Diesels produce more torque lower down the rev range, petrol engines produce their main power higher up.

Having said that it might be worth checking some basics like the air filter (also check the air intake system for any other obstructions) and the spark plugs.

Do you have the service history for the car? When was it last serviced?
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mtbskills

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Re: 2.5 V6 power and torque (lack of)
« Reply #2 on: 10 February 2010, 11:17:20 »
No real history unfortunately, but just did the filters, fluids, plugs etc myself, so should be somewhere near good !

I'll try a vacuum system check next, might be leaking somewhere    :y
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cmeonthemove

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Re: 2.5 V6 power and torque (lack of)
« Reply #3 on: 10 February 2010, 19:32:47 »
Is your V6 auto or manual?
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dbr

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Re: 2.5 V6 power and torque (lack of)
« Reply #4 on: 10 February 2010, 19:41:22 »
Quote
Bit disappointed with performance for a big (ish) v6, mainly lack of low down torque

Seems very flat below 3000rpm, better above that.

Multirams are operating (visually while revving engine), slight blow on centre section of exhaust.

Usually drive a D5 diesel volvo, which has loads of low down torque, so am I expecting too much
or can anyone suggest what to check next ... cant afford to replace exhaust yet   :(

Thanks  :y
gets even better above 4500rpm
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Andy H

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Re: 2.5 V6 power and torque (lack of)
« Reply #5 on: 10 February 2010, 19:46:05 »
I used to feel that my last Omega (manual 1994 2.5 V6) was gutless.

I recently switched to an automatic 2003 2.6 V6. Despite being auto it feels quite a lot stronger than the 2.5 did.

I changed the cambelt myself 3 times on the 2.5 but I didn't realise then that there was a special crank locking tool that I should have used. I am now curious as to whether performance would have been improved if I had used one :-/

The time has arrived to fit a new cam belt kit to my 2.6 so I need to get my hands on the cam/crank locking tool first.
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albitz

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Re: 2.5 V6 power and torque (lack of)
« Reply #6 on: 11 February 2010, 01:02:09 »
I am curious as to how you were lucky enough not to have 24 bent valves. :o ::)
But yes, if the cam timing was a tooth or two out on each cam it would affect performance and economy quite badly. :y
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Andy H

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Re: 2.5 V6 power and torque (lack of)
« Reply #7 on: 11 February 2010, 10:14:49 »
Quote
I am curious as to how you were lucky enough not to have 24 bent valves. :o ::)
But yes, if the cam timing was a tooth or two out on each cam it would affect performance and economy quite badly. :y
Give me some credit....

I have the cam locks, the cam belts come with markings that correspond with the marks on the pulleys and there are marks on the oil pump and cam cover backplate.

I also have the Haynes book of creative writing.....

With the tools available (& Tippex  ;)) I checked and rechecked the alignment. If the cam timing was inaccurate then it would have been due to innacurracy in the timing marks on the backplate.

I drove 70,000 miles in that car so I must have got the cam timing fairly close.

I did spend a long time checking the alignment. Strikes me that the time saved and the repeatabilty achieved using the crank locking tool & spectacles is reason enough to justify buying them. More accurate cam timing would be a bonus :y
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mtbskills

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Re: 2.5 V6 power and torque (lack of)
« Reply #8 on: 11 February 2010, 11:04:42 »
Its a manual, 120000 miles recorded  ::)

perhaps its just me becoming a lazy diesel driver then !

Strange thing happened last night, tried to start it from (very)cold, turning over fine but not catching, BUT, regular "thump" from engine as it turned over
Happened 3 times, took key out, back in then started perfect !

Any ideas ? Running ok now, fingers crossed  :)
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tigers_gonads

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Re: 2.5 V6 power and torque (lack of)
« Reply #9 on: 11 February 2010, 11:21:02 »
do a paperclip test mate  :y
guide in the maintenence section
see if they is any codes stored and then post them on here
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mtbskills

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Re: 2.5 V6 power and torque (lack of)
« Reply #10 on: 11 February 2010, 11:29:16 »
will do, thanks.  this weekend most prob
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mtbskills

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Re: 2.5 V6 power and torque (lack of)
« Reply #11 on: 19 February 2010, 11:27:13 »
right then, did the code test, only stored code was 31, but engine wasn't running so
this is normal ?

had the starting thing again, turning over with no sign of catching, then started fine after key out/ back in.

Immobiliser maybe ? Saying that, does it have one as standard ?

Your insight would be welcome   :y
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Andy H

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Re: 2.5 V6 power and torque (lack of)
« Reply #12 on: 19 February 2010, 11:49:42 »
Immobiliser is standard. On my very early (1994) V6 the immobiliser prevented the starter from turning. Don't know if it was different by 98 :-/

I think 31 is 'no RPM' so normal if the engine not running.

I did have a crank sensor fail which didn't bring up any code (other than 31) but that didn't cause a gradual power loss, it just refused to start outside the office (but did start after the AA had towed me the 10 miles home).
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mtbskills

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Re: 2.5 V6 power and torque (lack of)
« Reply #13 on: 19 February 2010, 12:34:11 »
just checked the codes, definitely no rpm so thats ok  :)

lots of posts on here about the crank sensor failing on these, might be worth doing anyway.

did you change yours yourself, andy ?
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mtbskills

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Re: 2.5 V6 power and torque (lack of)
« Reply #14 on: 19 February 2010, 13:14:46 »
just read the maintenance guide for the crank sensor, looks easy enough  :P

this is one helpful site !
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