Engine sounds & feels "rough" between 2500-3500 RPMs...

[DK327]

Hello all, so I took my T4R for another long distance trip, after a successful trip to KY last month (1600 miles round trip, no issues.) I hadn't gone over 70mph (2400 RPM) on the highway and there were no hills to warrant higher RPM's so this "symptom" went mostly unnoticed.

Well, this time the final destination was 5K feet above sea level so I had to use lower gears and higher RPM's and also on highway I still mostly drove at 70 mph but the speed limit was 80 so I had to sometimes go with the flow of traffic and not just chug along on the right late, with the trucks...

Anyway, when I'd go over 72mph (2600rpm's) the engine starts sounding kind of rough, louder than usual with maybe some extra vibration... There is no loss of power or anything but this continues till about 3500rpm and then it clears out and everything sounds smooth again.

This is the same in all gears and always within that RPM range, about 2500-3500 rpms, anything under or over is "smooth." I'm wondering if anyone else noticed something similar and what it could be... It's always done this ever since I first got the vehicle and I usually never go over 2500 rpms for prolonged periods of time so it hasn't bothered me much...

Thanks in advance!

 

[mtbtim]

Here's a thread with similar symptoms. Maybe you can find some answers from it.

http://www.toyota-4runner.org/3rd-g...0-rpm-under-acceleration-why-need-help-2.html

 

[DK327]

Did some more research on the forums and came across this:

http://www.toyota-4runner.org/3rd-g...0-rpm-under-acceleration-why-need-help-2.html

It sounds like it could be a couple of things according to [MENTION=94063]slapdappy[/MENTION] :

"Saggy transmission = misaligned driveshaft = vibration @ 2300-3000 rpm."

It was also recommended to pump the u-joints full of grease in the drive line until some squeezed out, regardless of the warnings about overfilling the slip joints... I'll probably be looking into these when I return from vacation next week.

 

[gamefreakgc]

Sometimes hesitation under full load like that is a fuel delivery issue, like what was mentioned. Start there, the filter is not too hard to replace with the right tools (just a bad location!) and costs about $30. The brake line wrenches that cover more than 4 sides of the nut will help prevent it from stripping if you have rust issues.

 

[DK327]

Sometimes hesitation under full load like that is a fuel delivery issue, like what was mentioned. Start there, the filter is not too hard to replace with the right tools (just a bad location!) and costs about $30. The brake line wrenches that cover more than 4 sides of the nut will help prevent it from stripping if you have rust issues.

Thanks for the response. The fuel filter was replaced with new OEM a few months ago. The symptoms described above were present with the old filter as well as the new one.

 

[mtbtim]

Since there's no loss of power, it doesn't sound like a fuel delivery issue.

 

[DK327]

Here is another post complaining about vibration at 2100-2500 rpm range, and solution that points to "missing bolts between the exhaust manifold and the cross over pipe which allowed it to vibrate. Replaced the nuts/studs that were missing and its significantly quieter"

http://www.toyota-4runner.org/3rd-g...le-specific-rpm-range-under-acceleration.html

This seems like it'll be a fun goose chase... It seems like anything could be causing this, even an "unbalanced flywheel" or a "hangar pushing up against the motor mount causing metal to mental contact." Those were some of the other vehicles that popped up during my search online...

 

[Troybylt]

I had this issue a little while back, solid mounts, well greased drive shaft, new fuel filter, new MAF, new TPS, no codes, no perceived loss of power, symptoms only present under load, etc. Ultimately I absolved to just believing it was one of my trucks particular quirks that is until it threw a code for Cylinder 6 misfire. It then proceeded to have some additional symptoms that ultimately got worse as time went on until I had to pull the injectors and change them. I got a new set of injectors from a junkyard and sent them to witch-hunter Performance to have them cleaned flow matched and have new baskets and O-rings put on and then when I got them back I pulled the injectors from my truck and tested the resistance on them all of the injectors from witch-hunter came back with resistance at roughly 16 ohms, the resistors that I pulled out of my truck were all around 18 ohms with the exception of Cylinder 6 which was roughly 46 ohms so that ended up being my problem. Apparently I had the issue since day one it just slowly got worse over the course of a few years. Until it threw a code.

I can't recommend witch hunter performance's service enough the cost wasn't too bad the turnaround time was very short and I cannot believe how much having flow match injectors woke up my tired old 5VZ, it feels like an entirely new motor now. Even if you're not having problems I highly recommend getting your injectors refurbished.