93 4Runner 3.0 with 231k+ miles so far. It runs and drives great, but it has a bit of a rough idle and at about 1500rpm it has a constant stumble or miss. If it sits at idle for a long period of time or if I'm out on the trails at low rpm it will throw a code 25 which from what I have been reading means it's lean? That doesn't make sense to me because if it smells extremely rich and I gag and just about die if I leave it running in the garage(with the doors open of course). To me it's running waaay rich, but the code says it might be running lean?

I'm thinking maybe the o2 sensor is shot or on it's way out? What about the TPS? I've replaced plugs, wires, cap, rotor, oil, air filter and adjusted the timing and nothing has helped. Any suggestions before I start buying more parts?

 

Apparently I was confusing a "rich" smell with a "coolant" smell. Blew a head gasket towing a trailer today. At least I know what was wrong now. Time to start ripping and tearing into this mess. Yippee.....

 

My compression check gave me a solid ~175 reading across the board.....until I hit #6 which had -0- compression. That's when I knew the heads had to come off and I was in for it.


Ran into a slight problem taking off the heads. All of the bolts on the crossover stripped out on me so I just cut the whore off. Instead of replacing that horribly designed setup I'm going to buy headers. I'd hate to get that damn thing back on and have to take it back off someday. Besides the power steering bracket being a PITA to remove the exhaust was my only other problem. As I was ripping things apart I couldn't believe how much crap needs to be dismantled to remove the heads on these motors. Might as well have removed the entire motor and made life easy.

 

So now it looks like what I thought *might* have been causing my -0- compression problem is actually a chipped valve and not a piston. I'm not sure if the head gasket was even blown now. I'm thinking it was a chipped valve. Ordered all new valves just incase one of the other valves thinks about doing this to me. Should have her back together better than ever by the end of next week.

 

Wow, that sucks! My truck is running rich too...

I hope your re-build goes smooth. For headers, check out LCE!

 

I wanted LC headers, but the price is just not reasonable considering it would be about half of what I paid for the truck. I went with Doug Thorley headers. It was about $535 shipped from Summit complete with the crossover.

I removed all of the EGR crap and the PAIR system. Now I forget where the power steering vac lines connected to, but I think I have an idea. I guess I will figure that out when the time comes.

 

Got my headers today. I must say, they are beautiful. Just waiting on my valves and head gasket set to get here.



My $0.15 EGR blockoff.