Fireworks in my Exhaust

[22SHO]

So, here's the deal. I just purchased a brand new 1991 SHO with only 112,000 miles on it! O-kay, it's not really brand new. The first thing I did was tow it home, put it on blocks and start tearing it apart. I have since replaced the plugs, wires, water pump, power steering pump, timing belt, acc. belts, valve cover gaskets, oil, filters, etc. Once I worked out the kinks of a few coolant leaks and power steering leeks, she was ready for action.

So, what's the deal? It sounds like there's a little fireworks display going on in my catalytic converters. The car was running a little rich, I think, so last night I replaced the O2 sensors and cleaned the MAF. I also think, based on some threads I've read, that the cats were plugged because the car seemed to hit a brick wall around 5500-6000 rpm. So, is the pinging from the exhaust just all the crap in the cats blowing up and burning out? In general, the noise sounds like I left a wrench in the crank case, but it does seem to come from the exhaust and it is accompanied by some coincidental puffing of the exhaust at the tail pipe(s). Is my theory correct? If so, will the cats clean themselves out or do they need to be replaced or is there anything I can do about it? If my theory of self cleaning clogged cats is wrong, does anyone have an alternative theory?

Any help would be greatly appreciated as I can no longer afford to put gas in my F-350 and commute it back and forth to work everyday.

 

[SHO#7]

Are you sure that the noise is coming from your exhaust? And if your converters are bad, I would refrain from the 6500 rpm range with fear of the intake sucking some bits back inside the motor. You can bang on the cats and listen for rattle type noises.

Had you ever heard the motor run before you dove inside it. Is there a chance that you loose wrench noise is a failing rod bearing? The oil pan is right next to the converters.

You can drop the "y" pipe and dump the guts out. And while it is off, do your rod bearings. The exhaust removal is the hardest part of it anyways.

Good luck and Welcome

 

[Ishodu]

Are you sure you got the plugs in the right order? The Chilton's manual is wrong if you used that. There have been a few posts on the forum of the proper routing of the plug wires if you wanna try a search you should find them.

 

[22SHO]

Thanks for the help. I did drive the car before I bought it and even drove it about 100 miles after the service and before the noise came about. The cars seems to have become progressively more allergic to high engine speed as time has passed and the pinging became significantly greater once the O2 sensors were replaced. It idles fine (other than the pinging) and runs O.K. in the lower rpm range. There are a couple things that have influenced my belief that it's the cats, or at least that the cats are plugged. While changing the plugs, wires, and valve cover gaskets, a fair amount of oil went into the cylinders from the plug holes. When the car was first started after the work was complete, the garage was absolutely filled with thick smoke and I'm sure the cats and the whole system got well coated with cold, used motor oil. Also, the puffing in the exhaust is in time with the pinging sound and the whole thing is very erratic and inconsistent.

All that having been said, I assume changing the rod bearings is probably not too difficult and perhaps worth it anyway? Most of the things I've read indicate that the bottom ends of these things are pretty bullet proof. Is that a true statement? Let me know what you think as I'm a little reluctant to drive the car much till I sort it out.

 

[Ishodu]

Letting all that oil and dirt in the plug hole is a bad idea. You should have gotten that stuff out of there before you removed the plugs. The motor is very strong but the weakest link is the rod bearings, they are not hard to replace and are not much money and are great insurance.