Hi, my buddy bought a 1997 four runner 4x4 automatic 3.4 v6. The truck was sitting and when he got it started it had a small misfire. No check engine light and it will not clear up. All of the cylinders hold pressure and there is no coolant in the oil or the other way around. He works at a junk yard so he asked around and he was told that since the truck has 200,000 miles it is most likely a chipped valve on the number six cylinder. I do not know how he knows it is in that cylinder but the guy has a lot of experience with toyotas. I was told I could buy the truck for $2000 and that it is red and in really good condition. No rust at all and it was owned by a doctor. My question is that if it were a valve, intake or exhaust, wouldn't a compression test show a leak or a slow leak? Is a chipped valve a common problem on this engine? He said that it misfires even at idle so it does not even need to be put under a load. Any suggestions would be great. I would love to get an idea of what it needs and buy it to drive myself.

 

I had the same issue, only mine turned out to be a bad injector. I was also getting code though. Did he check all the wires and boots? Change the plugs?

 

He did a compression test so he would have seen anything obvious.

 

Could be a vacuum leak somewhere...check all the hoses, intake tube, etc.

 

I am with Bobs4Runner....new plugs and check all the wires for cracks and whatnot on the wires themselves and the boot ends where they go over the plug. I know from experience about the boot end and a missing condition. There should be no cracks at all at the boot ends if you squeze them between your fingers ...something to check

 

I don't believe "chipped" valves are common. It is not an interference engine so timing chain damage can't do it. I would ask if you can replace the plugs and wires on it before buying. Then if it cleans up you got a great deal and if not it probably didn't cost you more than a diag fee at the dealer.

 

I understand that all the easy things should not be overlooked. My buddy got a zr2 s10 blazer that had the same sort of mis and one of the plugs was loose.

My main question was that if he did a compression test and everything was good than how could it be a chipped valve? If there was any problem with the valve than you would loose compression which would be why there is a misfire. Comments needed.

 

In order to chip a valve in the 3.4L, it would have had to break under the load of the compression, because the pistion wouldn't ever hit it. I have never heard of a chipped valve on these motors anyways. Yes, if it was chipped it would show up on a compression test or leak down test.

The most common problems with misfires on these engines have already been mentioned: Coil packs, injectors, wires, plugs. Weird that there is no code. One should pop up after around 25 miles of driving.

Other common problems could be the TPS or a dirty MAF but both will usually throw codes pretty quick.

 

Ok. I should just go and buy the truck. I had a 2000 corolla with no check engine light that had a bad mass air flow sensor. It can happen so I have to get a good look at the truck.