I know I have had issues with my vette and I have posted a lot trying to find whats wrong, I think I finally narrowed it down to having a collapsed catalytic converter :o. Unfortunately I have 3 of them. So instead of replacing all of them I would like to chunk the 2 that come of the headers and put a set of cutouts, and then just put a big catalytic converter in the back, where the 3rd one mount stock, so I can either run open headers or back through the large cat. Would It work (I mean would it pass inspection), if so what kind of cat could I put on there to make up for the work of the other 2? (its a 1989 Vette, 350sbc TPI, stock)

Also let me double check that its the cats: It hardly starts and when it does it runs very rough and I have to give it a lot of gas and when I back off the throttle to let it idle it drops to 400rpm and then just dies after a few seconds. Also its unresponsive when I pin the throttle to the floor it kinda chokes and then dies, and Its currently not drivable.

Thanks to anyone who posts

 

Have you ohm'd the injectors? A bad cat won't make a car harder to start. Run, yes...Start no. I suspect injectors or ignition or fuel supply.


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Any ceramic 400-cell aftermarket "main" cat should work in place of your old one to pass a sniffer-only emissions test. A 49-state legal cat these days is a 3-part vs 2-part catalyst of old. As such, they remove both hydrocarbons and NOx fumes.

If your state has a visual inspection, you simply need all 3.

 

Maybe pass a visial but will you pass the sniffer?

 

What makes you think it's the cats?

If your catalytic converters are not functioning properly they should be throwing a code at you.

 

well the car has taken 3-4 seconds to crank ever since we bought it, right now it will start but it will run very rough and the die on my if I completely let off the gas, so I think the startin for 3-4 seconds is another issue but why it wont run is another. One more thing thats really messed with my mind, after the car was towed how a few days ago it wouldn't start no matter how long you would crank, and I think I flooded the engine. so after a few days back on the charger I came back out and without starting it climbed under the hood and pulled a spark plug, grounded it and turned the engine a few times to check spark. then I put the plug back in and it fired up and ran rough again just like when it died on me at the intersection (No change).

Here is the link to very,very simular symptoms im having: http://forums.corvettefever.com/70/6...elp/index.html

 

I will check for the code today and let you know, I think its the cat because of all the symptoms im getting such as rough running poor gas milage and lack of power.

 

Check your fuel pressure also. I've had other GM vehicles act like yours when the fuel pump starts to go...

 

Checked the fuel pump and it seems to be fine.

 

The last car I had that the cats failed on made the exhaust manifold glow a bright pretty red.

 

Today I fired her up again with the computer hooked up and it says I have no DTC error codes but I am running open loop, also let me rephrase something; the car is hard to start but it will start. Also when I pin the gas to the floor it flat out chokes and dies (I can save it usually by catching it around 400 rpm but it still wants to die) or If I rev throttle to the floor the engine will spike up to 1000 rpm then before it drops to 900 if I hit it real hard again it will spike up to 1200 and then once more if I nail it hard before it drops to 1100 I can work its way to 1600 rpm but It wont stay there and when I let off it will usually give off a nice little pop, like a bit of a back fire and wants to die again. One more thing, I hear a rattle when I get on it from the underside of the car, at first I thought it was linkage that was rattling when I was driving but now I can hear it in the garage while being stationary (almost sounds like a rock in the exhaust) that's another thing that makes me think the honeycombs have broken down in the cats.

 

Take the front Y pipe off and see how it runs. That should prove the cats in or out. Everyone is guessing. Even is that is not it, a new front Y without cats and a new main cat is still a good idea.

 

You still have not told us if you've ohm'd the injectors. Mine ran like total crap before I installed the new ones and it would not throw a code either.

 

'89 vintage injectors are notorious for this. My Formula did
the same thing, ohm the injectors. Bad converters won't
throw a code on the older cars.

 

Same. It was a turbo car, and the turbo and manifold were red/white when the welds on the cat burst.

The symptoms you describe are similar to when my fuel filter was clogged on my old car.

 

sorry about that, I have not checked the injectors but when I bought the car the lady said she had new injectors installed on the car not long before we bought it, she did prove us with the receipts.

 

replaced the filter less then a few days ago, that's what we thought at first.

 

I don't think cats is your problem, and here's why.

Just recently my cats went out. My first warning was a sound smilar to what you described, rocks in a can. I used a stethescope and listened to engine from the top all the way down. The sound was most pronounced in the drivers side cat. But it was not that loud and intermittant, so I did nothing immediately as I wasn't positive.

About a week later I started getting a p430 code (catalyst system below threshold bank 2) this was the passenger side. The next day the rock sound was louder, much louder, like a spun bearing loud. There was gold flakey stuff coming out of the exhaust. Sure enough it was confirmed, my cats were breaking apart. Now, as to why I don't think this is your trouble...my car was running fine. If the catalytic material is making a rocks in a can sound, yes they are breaking apart, but there is still air flowing through the system and not choking the motor.

And if your cats were breaking apart, you would definitely be getting a code. Granted, my exhaust system is different, and my ecm is obdII, but the principle is still the same. Now if your cats were melted, they could clog the system, but they would not rattle so much.

1st) Make sure your engine is getting air. Check the filter, the maf, the throttle body.

2nd) make sure the engine is getting fuel. You said you checked the pressure and its good. What about the injectors? The fuel filter? the fuel quality/impurities. Could the injectors be leaking and flooding out the engine? Pull the plugs and see if they smell like gas. Check the oil and see if it smells like gas.

3rd) Make sure your engine is getting spark. Check your distributor cap. Is it carbon tracked? Is the rotor in proper working order? Is there a crack in the cap or the rotor? What shape are the plug wires in? Are they firmly connected to dist and the plugs? Try some dielectric grease on the connections in the boots. Is your timimg off? Could your hypertech chip have fried your ecm?

These are all things that are free and pretty simple to check first. The point is that there quite a few things that could cause this. Sometimes it can be the weirdest things. For example, one day my top radiator hose blew. No biggie right? Replaced the hose, filled with coolant, went to start, and no way. It would crank,crank,crank, chug a little smoke and die. Towed the darn thing home cussing like a sailor. I was sure my opti distributor was toast. Late at night, in a last ditch effort, I put some dielectric grease on the coil wire and it started right up and ran great. The coil boot had a pin hole in it and the antifreeze killed it. So check the simple little things first before you make up your mind on a guess and fix the wrong thing.

Yes, your cats may be on their way out, but I suspect something else is causing your starting/running issue. JMHO

 

My 1990 does something like this. crank and crank won't start and when it does it makes the rocks rattling in a can sound (detonation) the sometimes it just dies.

disconnect your est bypass wire and see if it runs normally, when I unplug mine my car starts right up. I also show no codes like you. great Fuel pressure, good injectors etc. etc.

I've never looked into why it does it but near as I can tell it is maxing out timing for some reason and not backing it off. I have heard tpi cars are designed to do this as a pre-start test so the knock sensor hears detonation. then ecm is supposed to back timing down which it doesn't appear to be doing. when my car does encounter this after it dies it never wants to start again. If it does feathering gas can keep it running but barely. Rpm at this time seems limited to about 2000rpm, and when let off gas the car just dies. I have punched cats as well so it isn't that.

I think your 3-5 second cranking before starting is normal and was part of the proms programming. basically till oil pressure is up no start. My 90 does this as well.

 

I will try the EST bypass wire when I get home, could you tell me were it is located?

 

@ jeffp1167: Yeah the more I look I think they play a role to some degree but not a large percentage unfortunately, so Im back to the drawing board, I have checked for fuel, air, and spark and they are all good. Also at first it would miss so we thought it was timing, if the ecm is fried then I guess that would make since, is there a way to test the ecm?