Vt s2 v6 ( flat spot/ power loss )

[foxrox]

I have a prob that 2 mechs and a auto elect couldn't figure out.The prob is a flat spot/power loss from idle to 2400rpm under load, the car has been scanned by all mechs with no codes. I've spent a fortune changing everything with no luck. The fuel system is fine, eletrically the same with the coil pack and dfi being changed over and again with no luck with plugs and leads the same. I had the auto elect change the computer again no luck, he had a mech mate drive the car and he thinks the trans could be the prob (trans was recond 12mths ago before I brought the car???????).I also changed the lifters recently because they were a bit noisy (the engine has done 270) thinking that could also be the problem and again no luck. As you could imagine I'am ripping my hair out so any input would be fantastic......Cheers steve

[graham7773]

Just a suggestion, check all your vacuum hoses for loose, split, hanging off (there is one at the back of the inlet manifold prone to this). check the valve that lets engine gas blowby back into the manifold for loose,(it should rattle when shaken) if the hose is hard or split, replace with new, check inlet manifold bolts and tighten if needed and only to specified torque. Make sure your fuel rail bolts are nipped down. Then look at your crank and cam angle sensors for dirt, oily deposits and clean. If any of your vacuum hoses are hard or split, replace them asap. Hope this helps

[foxrox]

Thanks for the reply graham,I intend on going right through the vacum side of things and the sensor issue is also valid being if they were dirty they would not always through a code....cheers

[foxrox]

I also forgot to add it only seens to do it when the temp rises above 1/4 as it is only very slight when cold.......

[VH commodore]

i think i have a very similar problem as you, only when it at operating temp. very annoying....im a 3rd year app mechanic and i got no idea, i have checked everything eninge wise and serviced the auto...im thinking it something to do with the auto/torque converter...

[VH commodore]

i thought it may have been the knock sensors stuffing up and retarding the timing, i tryed testing them but the results were inconclusive..

[foxrox]

yeh,it's doing my head in. I though about torque converter lockup but the mechs said it would be doing it all the time.....as suggested by graham I'll check the CAS for dirt ect, as the car was covered in red (desert like) dust when I brought it ???......it's worth shot,so if you figure it out let me know...cheers

[Cameron P]

im a newb but im gonna express my opinion anyway... so correct me if im wrong C=

if there was a problem with the lock up then take off would be sluggish as it wont allow the engine to rev more then the gearbox right?? and once you get over 2400rpm you will have more power to get going so thats why it is only sluggish under 2400rpm if that makes sense

just a theory as i've learnt a little bit about torque convertors :P

[Brett_jjj]

i thought it may have been the knock sensors stuffing up and retarding the timing, i tryed testing them but the results were inconclusive..

To test the knock sensors,just tap the alternator bracket or engine block with a hammer.The revs of the engine should noticably change if the knock sensors are working properly.

[showbags]

hey foxrox, i've been chasing the same problem with my vt for about 12 months. i've replaced every sensor on the engine,new plug and leads twice(just incase the first set were dodgy) new coils and dfi module, new injectors, new inlet manifold gaskets, new vac hoses,new air flow meter to no avail,it's still the same. i'm fitting a new harmonic balancer and crank angle sensor this weekend to see how that goes. if that doesn't work. i think i'll throw 20 litres of petrol and a match at it!

[Coast_Calais]

... I think i'll throw 20 litres of petrol and a match at it!

have you seen the price of fuel!!!!

[Coast_Calais]

oh, on topic.. soz..

I'm thinking CAS would be a good check first (easy)

But it sounds like your trans is locking up way too early... and it's only an effective lockup as it gets warmer.
drop by a trans shop mate, about 30 seconds of driving and they'll know if it's the trans!
(Or yourself, if you stab the loud pedal from a standstill, what revs are you getting? also note in gear at speed with lower revs, if you apply another 1/4 throttle do the revs increase in that gear or is it maintaining revs and just loaded up?)

[Cameron P]

thanks coast! thats pretty much what i was getting at but as i said... im a newb :P

[VH commodore]

the converter on mine isnt always locked...but i found when it does lock up at around 70 kph it takes its time un-locking when ur speed drops.....the prob seems to be related to temp as its much worse when at operating temp

[showbags]

replaced harmonic balancer abd cas last week end. still hasn't fix it. i was thinking some sort of heat sok issue, then this morning when i went to leave for work my radiator decided to drop its contents all over my garage floor. i'll replace that tommorrow and see what happens. don't trust you factory temp gauge either, mine sits half way between 1/4 and1/2 but the coolant temp was accually 112degrees! WTF!

[showbags]

replaced radiator, replaced coolant and bled system. went for a drive-all symptoms gone. running perfectly. 32 degree day went cruising around town for 45 minutes in stop start traffic(usually it would only take about 10 minutes to start playing up).

[foxrox]

Hey there,so do you thing it could have been your radiator all along? and have you had any problems since.....