Hi All,
This past summer I purchased an automatic 99 4runner 3.4 engine and 4x4 with 160000 miles. I have put almost 10k on it in the past 7 months, Its been a great rig, but is showing some issues:
I have been noticing engine lugging at high speeds between 40-60mph. When I accelerate to stop lugging, when the car downshifts and rev's up there is a loud rattling sound that is comming from the engine and only stops when it shifts up. The last time this happend up a hill the engine light started to flash. Any thoughts on what this could be?

 

What is the code related to the CEL (check engine light)?

 

Flashing engine light is likely a severe misfire. Occurring under load suggests cracked plug or leaking wire. The rattling may be the engine pinging. If it runs good otherwise I would start by replacing the plugs and wires. Be sure to use the ngk or denso twin grounded plugs and quality wires, such as ngk.

 

Brought her in today to check out the code and hear the noise. fairly certain its the plugs, gunna replace em all after it stops raining, and also run some lucus fuel treatment hopefully take care of the issue. Thanks for the help and advice folks.

 

Derkader, were you able to get this diagnosed? I'm experiencing a similar issue on a 2002 v6 auto 2wd 66k:

Slightly rough idle
loss of power at approx 4k rpm
When it downshifts, loud throaty rattling sound but still no power.

I'm having trouble keeping 60mph especially on long inclines on the highway.

Things I've checked/done:
Used the search button
Was throwing p0304, replaced coil pack with oem on cylinder 1, now cel is gone with no other codes.
Replaced all plugs/wires with oem
Cleaned MAF, replaced air filter.
Replaced fuel filter
Ran sea foam through gas tank, and poured directly in intake manifold
Measured resistance of injectors, all within spec (14.8 - 15.2 ohms)

Things I haven't done yet but want to and need gauges for:
Compression test, fuel pressure test, check that timing belt hasn't jumped (although my guess would be it'd result in low compression)

Any other ideas? Out of my googling, it seems as if my issues are most similar to yours. Thanks for any insight you might be able to provide!

 

02 w/ 66K ? I think its not fixable and you should sell it to me. Cheap!
Just Kidding!
No more check engine light? The way you describe it running, I would expect a light for sure. Sounds like maybe MAF issue. You could try unplugging it, then starting the truck and driving it. This will cause it to run on a pre-programmed fuel map.

 

This, or, what I was going to suggest was to unplug the battery and plug it back in to reset the computer. I had a similar issue and a simple computer reset fixed it for me.

 

Lol, yeah only 66k-it's basically a grocery getter for the mother in law and the primary transportation for the wife and me when we go to visit. I'm basically on vacation working on this 4runner.

When I pulled off the intake yesterday, I disconnected the battery so it should be reset by the time I put it back together. I just stopped by oreillys just now to borrow their fuel pressure tester and compression tester, so hopefully these tests all go well and I can test the ecu reset as well. I'll post an update on this. Thanks for the advice all. I really appreciate it!