Loss of Power

[Luke]

Hi Folks, upon return from a day trip my 2000 NM Pajero auto petrol was reduced to 40km/hr. Anything over this and the car spluttered until 40km/hr was reached again. I assume that it put itself in a 'limp home mode' which enabled me to travel the last 10kms home. All fluid levels appeared ok upon reaching home and there were no warning lamps flashing. Not being mechanically minded, is this something I can diagnose and have a go at myself or best left for my local mechanic or dare I say a Mitsubishi dealer with their specialst diagnostic equipment?

[trustytriton]

Rather than start a new thread, i can probably add to this one. I have a 1998 3L Auto Triton, and have experienced the same trouble (to varying degrees) on and off. Some times it just shows itself as a surging if i put my foot to the floor, and just not generating power. One time I got stuck doing 20 km/h for 80 km as i limped into Cobar at night. Half way along i drained and cleaned (as best i could) the fuel filter near rear passenger door (using a pen torch). It didn't help that much, and then i drained the tank completely at Cobar, and filled up and away i went, no problems. The problem seems to only arise when the tank is low, and i used to think it happened when it was hotter day, but i think this less now. I don't drive the car that much, so i just kept the tank more than half full. just the other day, I hadn't moved the car for a couple of months, and i drove it, and it started doing it after about 80km, and i was struggling to maintain 100km/h, and at lights it spluttered as it accelerated. Going through the other threads (and there are a few related to this topic) it seems that it can only relate to three areas
1) A partially blocked filter inside the tank (i am led to believe there is one)
2) a faulty fuel pump
3) a faulty ecu or related sensor

Now I believe i have a faulty ecu, as the car doesn't get the same fuel consumption as it used too. but that wouldn't make sense for diferent amounts of fuel in the tank making a difference.
So is it tank filter, or the fuel pump, or something else?

[Luke]

Interesting points Trusty Triton. It also happened to be a very hot day, lots of kms travelled with the air con on and the fuel tank was very low indeed. Coincidence? Anyway I'll take it to my mechanic for a look over and see what they come upwith.

[trustytriton]

Update

Had my Triton down at the dealer to check ECU. No problem there they reported. There was a bit of water in the tank, they added some metho. They also changed the fuel filter, tho it wasn't that bad that it should cause problems, and they also ran some stuff through the injector lines and injectors. They said fuel pressure ok. It was obvious that they were not confident, and they said the next step, if this didn't resolve it, was to pull the tank out.

The next day i took it on some tests. I did abit of driving around to get it warm, and as it warmed up i felt some subtle surging. Not as bad as the last time i had problems. It would let me do 100km/hr, but still there. I then went up Mt Dandenong road, from Ferntree Gully end. The fuel was low but no light on (usually indicating around 100km to go) There was again some subtle surging and the max i could get up the hill was 35km/hr. I went down the hill, and repeated the process, again 35km/hr. I then went and put half a tank of fuel in, and did the same thing twice more. 75km/hr up the hill both times, no surging. What does that say? I don't know.

I am heading into the dealer, to let them know what happened. How have you been going Luke?

[Jaydee]

[QUOTE=trustytriton;10287]
The fuel was low but no light on (usually indicating around 100km to go) There was again some subtle surging and the max i could get up the hill was 35km/hr. I went down the hill, and repeated the process, again 35km/hr. I then went and put half a tank of fuel in, and did the same thing twice more. 75km/hr up the hill both times, no surging. What does that say? I don't know.
[QUOTE]

Fuel pump is cavitating on low fuel levels perhaps ?

[trustytriton]

The Triton never did it until about 80,000 km, so it is definitely something that has happened to the fuel system which has caused a change. I was speaking to another guy, and he had experienced a fatigue crack in the fuel suction line between when it enters the top of the tank and goes down to the bottom. The result was that when it got below half it used to suck a bit of air, not enough to stall it, just to reduce power. The result is that it cavitates.

It sounds like a drop the tank out job, at least to check the tank and the suction line. Unless anyone has got any other ideas?

[demon]

Hi, just a thought , years ago when a Ford mechanic , had the same problem with some early falcons, finally traced it down to a crack on the pick-up pipe inside the tank and it would suck air when the fuel was low , when filled above the crack no problems.( the pick-up was not supported enough, we soldered a wire stay onto them to stop it wobbling )
It would be a much bigger problem on later models which run a much higher pump pressure.
Just a thought . Cheers Des,

[Luke]

Hi Trustytriton, I have been keeping the fuel above 1/4 full and had no problems. I will run some lower tank levels later as you have and see what happens. One suggestion made to me (by a mechanic) was to undo the fuel cap to release the pressure in the tank that can accumulate on hot days with low fuel.

[psproule]

Have you tried pulling the in-tank fuel filter and pump assembly? Look for obstructions to the pickup and look for mud in the filter (yes - mud). The filters are set for replacement every 100,000km. We pulled one out of our V6 NM at 80,000km and it was choked with a mud like substance.