could this be a cat problem
Thread Starter
Cruising
Joined: Feb 2006
Posts: 12
Likes: 0
could this be a cat problem
my 94 corvette knocks and clears up and then knocks when full throttle mostely when warmed up but a little when it is cold. The dealer did every test he could on it but could not find the problem, he said it needs to get bad till he can find the problem, but he said it could be one of the cats. Could this be my problem, one of them is bad
Burning Brakes
Joined: Apr 2006
Posts: 1,218
Likes: 7
From: Burleson Texas
when does it knock? what rpm? only under wot(wide open throttle)? what temp is the engine when this happens?
if its a clogged cat you should see higher engine temps than normal. the engine wont move so freeley when revved. and the cat or cats should be glowing red or extremely hot after a 30 min drive. and there ight have been tel tale signs before hand and currently like smell of rotten eggs from the exhaust.
i have been chasing a high rpm miss that i think im getting close to fixing. mine happenes between 4800-5500 at WOT. and gets worse the warmer the car gets. several members have had the same problem, and their fixes to the problem have varied. here are a few fixes, new tb gaskets(mainley the one on the top that leads to the crankcase), new maf, new battery, new opti, new plugs and wires, exhaust leak, and sea foaming (a product used to clean carbon deposits off valves, pistons etc.)
also how many miles on the car? any recent service done to the car? k&n filter? (the oil from the filter can coat the maff wires and cause a bad reading from the maf)
if its a clogged cat you should see higher engine temps than normal. the engine wont move so freeley when revved. and the cat or cats should be glowing red or extremely hot after a 30 min drive. and there ight have been tel tale signs before hand and currently like smell of rotten eggs from the exhaust.
i have been chasing a high rpm miss that i think im getting close to fixing. mine happenes between 4800-5500 at WOT. and gets worse the warmer the car gets. several members have had the same problem, and their fixes to the problem have varied. here are a few fixes, new tb gaskets(mainley the one on the top that leads to the crankcase), new maf, new battery, new opti, new plugs and wires, exhaust leak, and sea foaming (a product used to clean carbon deposits off valves, pistons etc.)
also how many miles on the car? any recent service done to the car? k&n filter? (the oil from the filter can coat the maff wires and cause a bad reading from the maf)
Thread Starter
Cruising
Joined: Feb 2006
Posts: 12
Likes: 0
its knocks/hesitates when passing a car, going up hills and hard on the gas. The temps around 200-245. 112687 miles now,new coil, new opti and plug wires at 86237 miles, new plugs 67568 miles and new o2s at 72352 miles (boches)
ac delco airfilter, new ICM at 110958 miles.
ac delco airfilter, new ICM at 110958 miles.
Thread Starter
Cruising
Joined: Feb 2006
Posts: 12
Likes: 0
my dad has a 94 too and my converters make a crackling sound all the time and my dads dont, I don't know if this matters but if you start the car and feel the pipe before the convertor's the pipe is hot and after the cat the pipe is cold.
and the temp is about 225 not 245 sorry
and the temp is about 225 not 245 sorry
Melting Slicks
Joined: Jun 2004
Posts: 3,032
Likes: 4
When my cat knocked...
It would only occur when the car was warm. Only while idling and very light throttle.
I had baseball sized chunks beating around the inside of the cat (and later I discovered some chunks made their way to - and got stuck in- the mufflers).
I determined the cause by letting the car warm up till I heard the knocking, then got under it and listening to where the sound was coming from.
Is it possible for you to duplicate the sound and diagnose like that?
It would only occur when the car was warm. Only while idling and very light throttle.
I had baseball sized chunks beating around the inside of the cat (and later I discovered some chunks made their way to - and got stuck in- the mufflers).
I determined the cause by letting the car warm up till I heard the knocking, then got under it and listening to where the sound was coming from.
Is it possible for you to duplicate the sound and diagnose like that?
