Rough acceleration in 4th

[mechagouki]

Something going on with my truck and I really don't have a clue what might be causing it.

The truck always runs a little rough when first started, and sounds like it's missing occasionally at idle, it also lopes just a tiny bit, the rev. needle moves up and down about 1mm when idling, but other than that it's generally run smoothly, and it does have a huge number of miles on it and no rebuilds.

Just last weekend I noticed a roughness/vibration right around 80kmh in 4th and around 95kmh in 5th, it smooths out if I accelerate through those speeds to about 90 in 4th and 105 in 5th.

Last night driving home I experimented a little, accelerating hard in 2nd, 3rd, and 4th gears. Acceleration past 3000rpm felt strong and smooth in 2nd and 3rd, but jamming my foot down in 4th caused a horrible deep vibration that rattled the trim inside the truck. The truck cruises smoothly in 4th at speeds below 75kmh and above 90. There is a huge hole in the muffler, if that's relevant.

I'm not in the least knowledgeable about engine/transmission stuff, just wondered if anybody could give me a clue what might be causing this?

 

[77'911]

You might get the muffler fixed, the lack of back pressure is contributing to some of the rough idle on start up. It will also run richer which might carbon and foul the plugs in the long run. On the vibrations, you might check the drive train mounts and the drive shaft joints.
regards

 

[priestsallore]

As '911 said, do you hear any abnormal rattling underneath inside of the cat itself? Check for vacuum leaks too. '911's post was about on target. If that doesn't work, check if your cat is clogging up or anything, as that can contribute to some of your lag.

 

[SV_Dude]

Correct me if I'm wrong but isn't back pressure a bad thing? You want a free flowing exhaust that reduces back pressure. The more back pressure you have then that is more that your engine has to work to expel the exhaust gases from the cylinders.

 

[priestsallore]

Correct me if I'm wrong but isn't back pressure a bad thing? You want a free flowing exhaust that reduces back pressure. The more back pressure you have then that is more that your engine has to work to expel the exhaust gases from the cylinders.

Good point. Though, the hole in the muffler is a bad thing... Where exactly is the hole?

 

[77'911]

Correct me if I'm wrong but isn't back pressure a bad thing? You want a free flowing exhaust that reduces back pressure. The more back pressure you have then that is more that your engine has to work to expel the exhaust gases from the cylinders.

Standard engines(ie not turbo charged,.....) are designed, and need a degree of back pressure to run properly. One can argue if the factory setting is optimum for performance, but virtually zero back pressure is a bad thing, especially on that type of engine(ie 4 cyl). The last thing you want is a ton of fuel dumping down the cylinder walls.
regards

 

[4runnerBrett]

Standard engines(ie not turbo charged,.....) are designed, and need a degree of back pressure to run properly. One can argue if the factory setting is optimum for performance, but virtually zero back pressure is a bad thing, especially on that type of engine(ie 4 cyl). The last thing you want is a ton of fuel dumping down the cylinder walls.
regards

This

 

[mechagouki]

The whole muffler is shot, the outer heat shield is just held in place with two hose of those stainless clamps like you put of a dryer vent. Just another job I want to do but can't afford:moping:

I also haven't checked any of the drive or transfer fluids since I bought the truck a year ago and I've put maybe 15-20,000 kms on it since then; I know, I know, I'm an *******, but I just don't have much $$$ to put into the truck.

What should I be filling the drives and transfer case with? Someone told me to use that Lucas goop as it is good for high mileage drivetrains?

 

[priestsallore]

Take the guts out of the cat, buy new pipe & weld it all in. The more you wait & dont fix it all, the more of a hassle & money youll have to dump.