Possible Bad Cat Problem?
 

Hey all, figured I've been having soo many problems lately with my truck I might as well sign up here.

Truck in question: 97 Chevy Silverado 1500 v8 5.7


To start it off, about a month ago I put about 1k worth of parts in trying to fix a problem which ended up being either the Fuel Pressure Regulator or the Fuel Injectors. ( at that point i was just fed up and spent the money to replace the whole thing).

I replaced everything from the fuel pump, fuel filter, fuel relay, distributor, cap, rotor, plugs, wires, ignition coil and the injectors. needless to say i learned alot in that week or so.

It ran fine for about a month or so, kinda rough idling and accelerating. I did have a code that i cant remember the actual number but it looked to be a timing problem.

I had a friend more experienced than i look at it. he was able to get rid of the original code, but then i had the codes p0420 and p0430. which are for the o2 sensors by the cat. i cleared them since at that point the truck was still running just to see if they would come back. they did.


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a couple days ago i was driving to pepboys and as soo as i pulled into the parking lot my truck sputtered and died. I was able to start it enough to pull into a spot and it sputtered and died.

i got it towed back to my work and had a friend look at it again. I was getting the codes p0420, p0430, and p0108.

after some hopeful starting i ran the code again. p0107.

since then I've replaced the crank position sensor and the MAP sensor.I've tried to start the truck with and without the map sensor plugged in and nothing. It now sits there mocking me, I go to turn it on and the engine gets gas but it almost seems as if it's not getting any spark.


I was wondering if a bad cat could hinder the truck from even starting like the way it is. From my research it's looking like I have a bad cat for sure. any opinions?

Oh, jeez, I have to say the short answer is yes. The catalytic converters are probably toast from unburned fuel being dumped out the exhaust while the shop kept throwing new parts at it. There's a small chance that P0107 is a damaged VCM as well. I'd shoot the mechanic and demand my money back.

I don't know what the original problem was but P0420, P0430 codes are almost always the catalytic converters. P0108 says the MAP sensor read too much air pressure at the given throttle, i.e., too little vacuum inside the intake manifold. Sometimes this is an indication of a restrictive exhaust, e.g., melted/fused catalysts. P0107 says the MAP sensor read too little air pressure. It could be a wiring problem, depending on what it read, or the VCM, given the flip-flop. The freeze frame data would help clarify.

Could be the cat... or first 02 sensor.
A bad map sensor will cause hesitations .. even no crank.

I would shoot the mechanic, but I'm against suicide. haha.

Thanks for your help though. I do appreciate it. Like I said from my research it sounded like my catalytic went bad so I figured I'd double check my case. From the sounds of it, the majority of the problems would be cause by a bad one.

Thanks for the help again guys.

Unbolt the cats from the manifolds and drive it. If it run fine with plenty of power the cats are the problem.

decided to tuck in my pride and take it to a mechanic. a day later they said theyre replacing the pcm module. hopefully this fix is long enough for me to sell it and buy a friends 2005 2500 hd off of him.

Hope that's all there's to it. Thanks for the update.:)

Me too. I'll update again monday when I actually get it back, for some closure.