Heh, I guess I hijacked the post. Sorry. The head is out, and the tops of #1 and #2 pistons are MELTED. Wow. That's all I can really say. The block is going back to the macinist for investigation. It looks like $1000 down the tube for now, but we'll see what he says. I'll see if I can get pics of the damage. It was pretty shocking...

Check your EGR for proper functioning. The passage from the EGR valve to the EGR hole in the floor of the intake plenum, behind the throttle body, must be clear. Mine was all carboned up. Lack of EGR can cause high combustion chamber temps, hence the pinging you were getting.

Check the harmonic balancer, if the pulley slipped you could have been unknowingly giving it too much timing advance.

Check the cat and muffler for clogging/restrictions.

You might also give Jerry Lemond a holler, I bet he's seen this type of problem before.

Good Luck, let us know what the autopsy reveals.....ed

Thanks Ed. I'll look into the things you listed. I ran a brand new cat with a plug in the O2 sensor whole for a while since I couldn't get the old sensor out of the stock manifold. The cat very well could be clogged from running rich. The EGR tube got looked at when I had it apart, but I'll give it a cleaning anyway.

Update: The motor is apart and getting re-bored to .040 over. I guess it's a good thing I didn't go all the way the first time. I took the pistons to be examined and was told that the damage looked like it was caused by "severe detonation" due to a "lean" condition. The pistons in #1 and 2 cylinders were HAMMERED. The rings were seized in the grooves from heat, and it looked like they tried to sieze. Luckily, the crank and rods look ok. The pistons got hot enough to turn the wrist pins blue.

I think I'll try to have the injectors checked (or put new ones in if I can't find anyone with bench tester) and change the EGR valve and backpressure transducer. I really can't afford to burn up another motor (I couldn't afford this one). Any other advice? The truck has to be running and broken in before my grandparents take it to Oklahoma in mid-December, and I still have to get a cruise control system set up for them.

Thanks for all the help!

BTW, please keep in mind that this is a '94 2.6 from AirAmigo's truck with '90 running gear and accessories.

Jon, Yikes <img src="/forums/images/graemlins/shocked.gif" alt="" /> Hope it goes better this time.

Ed, so now I'm thinking I'd like to get my EGR working,especially after Jon's experience. do you think a person can clean out the EGR passage in the intake manifold without removing the manifold? I know mine is plugged, as I saw it when it was off a couple years ago.

Rick, on a tip from Jerry Lemond I was able to clean mine out without pulling the manifold. The EGR dumps into the throat of the intake plenum, just inside of where the Throttle Body mounts. You'll need to pull the plastic intake air tube assy and other various interference items to get access to the TB in order to unbolt it. I didn't want to have to pull the TB all the way out, because of all the little coolant hoses on the bottom that are such a pain. I was able to remove all (4) nut/bolts, and separate the TB enough from the intake plenum to be able to see into and get a wire into the EGR passage.

It's on the floor of the throat of the plenum, and on mine it was so gunked up with oily deposits that if I hadn't been told it was there, I woudn't have found it. It's got a sort of a chamfer to it, in order to help the exhaust gasses get in.

This hole leads to the main EGR passage which goes aft in the head. There's a blind plug at the back of the head which opens up into the end of the passage. Also another smaller passage at right angles, in front of where the EGR mounts, and accessible from the inboard side of the head. The EGR dumps into this package. So, by removing the EGR, 2 plugs at the rear areas of the head, and the TB, you can get at all the areas accessible to start cleaning. You can blow air back and forth to check for free flow/clogs. You can also tape a smaller tube to a vacuum hose and suction debris out of the various passages.

What I was able to do was to stick various wires and other flexible cleaning utensils (.090 Weedeater line worked great!) into the EGR passage in the intake plenum and that's where I found my clog. Sucked all the gunk out of there I could, swaged it out, blew out what I could, and reassembled. Knew it was clean when I depressed the EGR vlv and got a ratty idle.

If your passages are more badly clogged, you may be able to loosen them up with carbon dissolving spray. I did spray some Seafoam Deep Creep into the plenum to help clean off some of the oily deposits inside. I smoked like the dickens when I lit it back off.

Seems fine now. Just got back from a 150 mile trip from Poulsbo, WA, to Spanaway, to Shelton, and back to Bremerton, she's running like a champ even with a passenger and a 3.1 Rodeo V6 in the back! The little 2.6 doesn't seem to care much if it's dragging a load around, it just torques right along.

Anyway, if you have success with the above, it's all great. If your intake is so badly clogged with caked-in deposits that you can't chip them out with hammer and chisel, you may have no choice but to pull the intake and take it all apart or replace. Definitely not a fun job without pulling the head, too.

My impression was that the intake plenum area looks like it can have a tendency to build up these oily deposits and I bet it's one of the most common areas for a clog to occur.

HTH and G'Luck.................ed