Outer Limits 4x4 Board

Hi All,

I have lost alot of bottom end torque in my MK V6 3.0L Triton. I have put 31" tyres on it however I didnt notice the loss of power when I did it.

Does anyone have any suggestions as to what I can check?

It has a new air filter etc etc.

Thanks

Air Flow Meter or check fuel pressure. AFM's are pretty common but expensive. Try cleaning it with a very light solvent and see if it improves.

I was lacking down low power in my 3lt. Pulled the return line off while running and no fuel was returning to the tank. Replaced the crappy Fuelmiser pump with a Bosch one and the car has never run so well.

Not saying that it is the fuel pump. but I would expect that if the pump was sus, it would starve the engine for fuel at high loads - high revs/high load. I would be looking for a vacuum hose either fallen off or perished, whic allows air to get into the engine at low revs, mucking up the air/fuel ratios.

Another possibility is a spark plug or lead breaking down.

date wrote:Not saying that it is the fuel pump. but I would expect that if the pump was sus, it would starve the engine for fuel at high loads - high revs/high load. I would be looking for a vacuum hose either fallen off or perished, whic allows air to get into the engine at low revs, mucking up the air/fuel ratios.

Another possibility is a spark plug or lead breaking down.

Sorry date, but i bed to differ. Engine "load" and demand for fuel is quite high when at low revs, especially when trying to turn 33" tyres (in my case) from a static start. Once moving with bigger diameter tyres there is a lot less engine load required to maintain speed. In my case, it was very sluggish off the line and took a lot of right foot to take off and get up to speed. Once moving, the engine felt as normal. I assure you that when fuel pressure and flow was increased from fitting a descent, genuine Bosch pump, i can now actually spin the 33's off the line. Top end revs did also increase.

Shaun, does it have a missfire down low or is it just lacking torque, power? If there is no missfire i would rule out an electrical fault like plugs, leads etc. I would put a fuel gauge in line to determine whether correct fuel pressure is being met. Roughly 300kpa @ idle and 350kpa when revving or with the vacuum line to the reg disconnected. If this is within specs then i would be turning my attention towards and AFM out of range (quite common on these especially if they are used offroad in dusty conditions) or possibly injectors that may be down on flow. A good test for this is to clamp the return line off at idle and if the idle improves then its possible that the injectors require cleaning or replacing. Hope this helps.

Hudson44: Whilst you are on the right track, I strongly suspect that an engine at full throttle at, say 1500 R/min, will use considerably less fuel than one at full throttle (at say 5000R/min), meaning that if it was the fuel pump or filter causing the problem, it would be obvious at the higher revs/loading. Anyway, the torque output at lower revs is way down on its peak levels (around 3000 R/min).

You can be running on 5 cylinders and it will still run smoothly, albeit with noticeable less power over the whole range. I still suspect an air leak somewhere - this will lean out the mizture at low revs and because the leak is relatively small, at higher revs ithe leaning effect will be less noticeable.

Sweet man, thanks for the tip. Can you please explain to me how I had a dramatic , extremely noticable increase in bottom end torque when A new pump was fitted thus bringing the pressure and flow back to normal?

hudson44 wrote:Sweet man, thanks for the tip. Can you please explain to me how I had a dramatic , extremely noticable increase in bottom end torque when A new pump was fitted thus bringing the pressure and flow back to normal?

Semi-random guess: fuel injectors generally work best within a defined pressure range - too high or too low and the spray pattern is wrong.

If your dud fuel pump wasn't producing enough pressure to permit the injectors to generate a decent spray pattern that could affect low rpm torque (inadequate fuel dispersion, incomplete combustion) but at higher rpm the higher air flow might improve fuel dispersion enough to generate close to normal performance.

At a guess.

I'd say you would be spot on Scott, hence why I suggested this as a possible fault in my first post. I've still got my money on a faulty Afm though.

Is it the flux capacitor?

NJV6 wrote:Is it the flux capacitor?

That was my next guess!

hudson44 wrote:

NJV6 wrote:Is it the flux capacitor?

That was my next guess!

Really? Surely he should change the blinker fluid and adjust the wiper shims before spending that much?

Hi Shaun.

If you are near SE Qld you can come over tomorrow and watch me put new rocker cover gaskets on my 3l v6 triton.

OH the joy.

Rod

.

hudson44 wrote:

date wrote:Not saying that it is the fuel pump. but I would expect that if the pump was sus, it would starve the engine for fuel at high loads - high revs/high load. I would be looking for a vacuum hose either fallen off or perished, whic allows air to get into the engine at low revs, mucking up the air/fuel ratios.

Another possibility is a spark plug or lead breaking down.

Sorry date, but i bed to differ. Engine "load" and demand for fuel is quite high when at low revs, especially when trying to turn 33" tyres (in my case) from a static start. Once moving with bigger diameter tyres there is a lot less engine load required to maintain speed. In my case, it was very sluggish off the line and took a lot of right foot to take off and get up to speed. Once moving, the engine felt as normal. I assure you that when fuel pressure and flow was increased from fitting a descent, genuine Bosch pump, i can now actually spin the 33's off the line. Top end revs did also increase.

Shaun, does it have a missfire down low or is it just lacking torque, power? If there is no missfire i would rule out an electrical fault like plugs, leads etc. I would put a fuel gauge in line to determine whether correct fuel pressure is being met. Roughly 300kpa @ idle and 350kpa when revving or with the vacuum line to the reg disconnected. If this is within specs then i would be turning my attention towards and AFM out of range (quite common on these especially if they are used offroad in dusty conditions) or possibly injectors that may be down on flow. A good test for this is to clamp the return line off at idle and if the idle improves then its possible that the injectors require cleaning or replacing. Hope this helps.

No misses what soever, just lacking in torque. Once up to speed its fine......

Thanks to all for your input.

where is the fuel pump on the 3 ltr mk triton ? might change mine around see if that fixes my problem

Probably way way off field, but how long since the timing belt was changed, and how tight is it? If it has slipped a tooth or two, that will affect the performance greatly, and more importantly, if it slips teeth again, could cause major engine damage. I hope it isn't this, but it may be worth checking.

Thanks guys, Is it easy to check the timing on these, I have a timing light etc??

Cheers

Not sure of your vehicle, but on mine (an NL Pajero), I cannot even see the spark plug leads, netherthless get to them and clip on a timing light. The way to do mine (and probably yours) is to remove the timing belt covers, align the thing at TDC (by the timing mark on the Crankshaft pulley) and check the index marks on the cam pulleys. A bit of a fiddle. If you can do it by a timing light it would be far easier and give you the same answer.