I just bought a 92 5speed V6 4runner and it was running rough when i got it, thought it was just the plugs or wires bc it seemed to just be missing. I have changed the plugs, wires, cap and rotor as well as the fuel filter with factory denso stuff and its running a little better but still runs like a dog especially anthing under 2500 rpm and under a load. no check engine light, but my 4wd light does not come on so im not sure if there should be a check engine light on or not. Going 75-80 down the interstate it runs ok but accelerating and going up hills or going 35 in 4th for example it has no power at all. It idles rough almost like its got bad plugs, and at low rpm under a load it really lugs and is really rough and feels like a 5hp briggs and stratton. Ive driven many toys, including a 3.0 5speed pickup and i was very impressed with its power but this thing is nothing close, if you drove it and i told you it was a 4cyl youd still think something was wrong. Im thinking something with the fuel system (clogged injectors maybe) since i know the ignitions good, air filter etc is ok and although i cant say for sure but it doesnt feel like the same cylinder is the one missing every time. The previous owner said he had a complete top end job done on it about 15-20k ago, new valves etc and its got 129k total on it but he didnt have a reciept to prove it. Anybody got any ideas? thanks Michael

 

When I bought my 94 runner a couple years ago it was running rough. The dealership said it was the headgasket, but when I took it apart, the valves were just adjusted wrong. Though I took the time to replace the headgaskets anyways, which I found out were in good shape and wasn't the problem. So do a valve check, and make sure they are adjusted properly. Get a Chiltons or some other maintenance book for your runner and it'll tell you how... And then again, it might be the headgasket, and it was not really replaced 20k miles ago, or they did something wrong... Hope I've helped.

 

was it running rough across the entire band or just low rpm? Thanks

 

at idle, and just low rpm's, when reved above around 2500 it smoothed out. I drove it that way for a couple of months and it kept getting worse. But now its fine, and has been ever since...

 

Sounds the same, looks like this might be my prob. Thanks for your help.

 

i had somethin like that happen, maybe not as extreme as you put it

*might* be the EGR modulator valve, mine needed to be replaced when i bought my v6 truck, and it fixed the problem i was having

 

Pull the codes before you do anything. Could be an EGR valve or an o2 sensor. Codes will put you in the right direction.

 

Run a compression check I would bet its valve adjustment or a burned valve. Mine was doing the same thing after 8k miles of DOA junk. Turns out I had 60 PSI in 3 cyls due to bargan basement valves that self destructed after 8k.

 

check timing too

 

Yeah i forgot to mention i checked the timing already, it was a hair off, i adjusted it and it didnt really make much a difference, main problems still there. I should have checked the compression while i was changin the plugs but i really thought the ignition was the culprit. Thanks everybody for all of the ideas.

 

I think im gonna break down and buy a import cartridge for my buddies mac scanner before i go throwin anymore parts at it, between the 4runner and the taco it will more than pay for itself.

 

The 92 is OBD1 meaning its not standardized at all.
The taco is OBD2.

I would just pull the codes on the 92 manually with out the scanner. The scanner wont give you any more info than the CEL on the older 92 model.

 

by checking the compression it'll be easy to tell which vavle it is, but you still should check all the valves anyways...