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rotten eggs

davec0_17

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Joined
Feb 7, 2006
Messages
164
Location
Houston, PA
Corvette
1994 black 6 speed, cat back flowmasters
My car has been running rough for a couple hundred miles now, on and off, and seemed to get a little worst this morning. I pulled it in the garage, and the odor diagnosised the problem. I read the cats don't go bad very often, so I'm guessing O2 sensor(s). Could I unplug the sensors, and drive the car to make sure the cat is not plugged up? The check engine light has not come on at this point.
 

davec0_17

Well-known member
Joined
Feb 7, 2006
Messages
164
Location
Houston, PA
Corvette
1994 black 6 speed, cat back flowmasters
It seems to come and go. If the cat(s) where clogged, wouldn't they be blocked all the time? If I floor it, it still seems to have power. Low RPMs, it will chug up a incline, where as before 1500 RPM was nothing, just went right up. If I unplug the sensors, how bad would the car run, like after it warmed up?
 

Vanity Plate Bob

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Joined
Apr 8, 2002
Messages
722
Location
Johnstown, Pa, USA
Can't help any more. There are web sites covering the smell. Do web search. There are a number of sights concerning cat smell. I'm sure there wll be more advice via your request,here.
 

jmccloud

Well-known member
Joined
Feb 1, 2003
Messages
694
Location
Maryland
Corvette
1995 White Coupe LT-1 Auto
Rotten egg odor

The rotten egg odor comes from the cats working to burn off something 'rotten' that came from the motor, not from a bad cat. Since it's been running rough for a while, the cats are likely just doing their job burning off excell fuel. If the O2 sensors go bad, you may be running really rich therefore overworking the cats. Any codes? Or can you get a scanner to measure O2 sensor voltage during operation?
It could be something drastic like oil burning but look for the simple stuff first, like O2 sensors (because of the rough running). Could also be a bad plug or burnt plug wire or stuck EGR; anything that would lead to misfire.
Good luck and please post the solution when you find it.
PS Plugged cats cause poor high rpm performance.
 

davec0_17

Well-known member
Joined
Feb 7, 2006
Messages
164
Location
Houston, PA
Corvette
1994 black 6 speed, cat back flowmasters
I will have to stop at a parts store when its acting up, hopefully they can read the sensors. It has not set the CEL, so there should be no codes set. The car has 40,000 miles, and most of the time still runs great.
 

davec0_17

Well-known member
Joined
Feb 7, 2006
Messages
164
Location
Houston, PA
Corvette
1994 black 6 speed, cat back flowmasters
A call to a couple parts stores, they can't read the A/F sensors. If the light was on, they can read the code. Looks like it might be tool buying time!
Thanks for the help, I appreciate it.
 

G Winter

Well-known member
Joined
Aug 21, 2004
Messages
2,177
Location
NW Iowa
Corvette
1990 red convert 6 sp
How does the car start warm after sitting for a few min.? You may just have an injector or injectors leaking. get a pressure gauge and check for leakdown.


Glenn
:w
 

davec0_17

Well-known member
Joined
Feb 7, 2006
Messages
164
Location
Houston, PA
Corvette
1994 black 6 speed, cat back flowmasters
It starts fine, hot and cold. I pulled the EGR, and it looks fine. I checked the cat temperature about 15 minutes after I shut it off this afternoon, and the pasenger one was 40 degrees hotter (285 verus 242)than the drivers. It seems to be fine cold, and then the miss comes in as the engine warms up.
 

G Winter

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Joined
Aug 21, 2004
Messages
2,177
Location
NW Iowa
Corvette
1990 red convert 6 sp
My 90 ran fine cold and developed a miss when it warmed up. I had two bad injectors, ohmage was low , should be about 16 ohms and as down to 7 . Replaced them and miss was gone. The ecm may richen the mixture with a couple of lean cyl. Messes with the o2 sensors.

Glenn
:w
 

John Robinson

Gone but not forgotten
Joined
May 3, 2005
Messages
1,555
Location
Muncie, Indiana
Corvette
1993 Polo Green Coupe
Another Question

Just before this started did you fill the tank? Are you still on the same tank as you were when it started? If you are on the same tank I go along with the earlier post that you may have some bad gas causing your systems.:crazy
 

davec0_17

Well-known member
Joined
Feb 7, 2006
Messages
164
Location
Houston, PA
Corvette
1994 black 6 speed, cat back flowmasters
No, it started before I got gas. But with the high fuel prices, I sometimes would add 1/2 tank of mid grade on top of the premium (here mid grade is 89,premium is 93 octane) that was in the tank.
Drove the car today, about 10 miles, ate breakfast, drove 10 miles back home, and it ran like a champ.
 

davec0_17

Well-known member
Joined
Feb 7, 2006
Messages
164
Location
Houston, PA
Corvette
1994 black 6 speed, cat back flowmasters
My 90 ran fine cold and developed a miss when it warmed up. I had two bad injectors, ohmage was low , should be about 16 ohms and as down to 7 . Replaced them and miss was gone. The ecm may richen the mixture with a couple of lean cyl. Messes with the o2 sensors.

Glenn
:w
Thanks Glen,
I think I'm looking at either bad plug wires or injector(s). Question, do I need a special injector meter to check the injectors ohm's? My meter goes right to 0 when I put both contacts on the injector. I have the injector unpluged, with the fuel pressure released.
 

jmccloud

Well-known member
Joined
Feb 1, 2003
Messages
694
Location
Maryland
Corvette
1995 White Coupe LT-1 Auto
Injector resistance

Make sure the ohm-meter scale is set to ohms rather than khoms or mohms, unless the meter is an auto-ranging meter. 16 ohms will read as zero on either the kohms (1000) or the mohms (1000000) scale.
Bad wires will usually show sparks if you view the running engine at night with all lights off and in a dark area (unplug the under hood lamps). Also, the engine will miss noticably under load (higher gear or 'lugging' the engine). Humid weather often exaggerates bad wires causing arcing.
Stinky operation with good performance is usually from running rich; either injectors or O2 sensors.
Regarding your initial question of whether bad cats would always be bad, sometimes they break up inside and due to shifting parts will plug or not and cause intermittent poor/good performance, even at high rpm.
 

davec0_17

Well-known member
Joined
Feb 7, 2006
Messages
164
Location
Houston, PA
Corvette
1994 black 6 speed, cat back flowmasters
It's an OHMs meter, and I've tested it on other circuts so I'm sure it works. But I'll be damned if I can get anything other than a zero reading out of all these injectors. It's like I'm just touching the prongs together. They are still in the fuel rail on the car, do they need grounded or something?
I tried looking at the wires in the dark, thought the engine was cold in my garage. I sprayed some water on them, and got some VERY light sparks on some. Not sure thats enough to be my problem?
 

davec0_17

Well-known member
Joined
Feb 7, 2006
Messages
164
Location
Houston, PA
Corvette
1994 black 6 speed, cat back flowmasters
First off, thats for everyone who helped me work through this. It turned out to be plug wires and plugs, $54 later and I'm on the road again. I also had rust for some reason in the #7 hole of the distributor cap, and that caused the wire end to be froze in the #7 hole. I didn't realize till I removed the insert from the end of the spark plug wire from the cap, which detached inself when I tried to remove the boot/wire from the cap. (That in itself took and hour, I'm lucky the cap didn't crack/break!) I cleaned the #7 hole in the cap as best I could, put some electical grease in there, new Autolite wires, Bosch platinum plugs, $54 includes shipping to my house, and the miss is gone. Hoorah!
 
H

HD2HVETTE

Guest
Smell normally would be either rich condition or bad converter. My guess would be the converter since it runs OK until they heat up.
 

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