California spec catalytic converter
#1
08-03-2010, 09:58 PM
Bad catalytic converter issues
A few days ago, I had a new California-spec catalytic converter installed on my '94 3.4L ... These new catalytic converters are supposed to remove more pollutants from the car's exhaust than the catalytic converters sold in the other 49 states. Since I had it installed, however, my "service engine" light has been coming on. It'll be off at first when I start driving, but after I've been driving for 5 minutes or so, it'll come on and stay on until I turn the car off.
Is this something I should be concerned with? Or is this new catalytic converter causing the emission sensors to read differently and therefore causing the light to come on? Are there any other California Camaro owners here who have had one of these new catalytic converters installed? And did you experience the same thing?
Other than the "service engine" light being on, the car is running better than ever. And the funny thing is that before, when the old catalytic converter was all broken up inside and the car was running terribly, the light never came on.
Is this something I should be concerned with? Or is this new catalytic converter causing the emission sensors to read differently and therefore causing the light to come on? Are there any other California Camaro owners here who have had one of these new catalytic converters installed? And did you experience the same thing?
Other than the "service engine" light being on, the car is running better than ever. And the funny thing is that before, when the old catalytic converter was all broken up inside and the car was running terribly, the light never came on.
Last edited by wiskow; 08-04-2010 at 06:42 PM.
#2
08-04-2010, 07:28 AM
You should have Autozone or another parts place or repair shop check for codes while the engine is running. Something is definitely wrong. Replacing the converter should not cause the SES light to turn on since all the things that trigger the light are located *upstream* of the converter. After the converter it's just pipes and a muffler, no sensors.
Why did you have your converter replaced? Do you know what brand/part number converter was installed? I'd be interested to know that.
AFAIK the only way to check catalytic converter operation on a pre-1996 vehicle (1995 on very few models) is to use a separate tester and a probe that is shoved up the tailpipe. That's what we do here in Pennsylvania. Every year you have to get the emissions checked at a facility that has a computer/tester hooked up via phone lines to Harrisburg (the state Capitol).
I have a 94 with the 3.4 and the factory-installed converter is pretty big (high oxygen storage capacity) and has low flow resistance (ceramic matrix). This is unlike the pellet bed converters used from the mid-70s into the early 80s. Those converters sucked.
Why did you have your converter replaced? Do you know what brand/part number converter was installed? I'd be interested to know that.
AFAIK the only way to check catalytic converter operation on a pre-1996 vehicle (1995 on very few models) is to use a separate tester and a probe that is shoved up the tailpipe. That's what we do here in Pennsylvania. Every year you have to get the emissions checked at a facility that has a computer/tester hooked up via phone lines to Harrisburg (the state Capitol).
I have a 94 with the 3.4 and the factory-installed converter is pretty big (high oxygen storage capacity) and has low flow resistance (ceramic matrix). This is unlike the pellet bed converters used from the mid-70s into the early 80s. Those converters sucked.
Last edited by 1augapfel; 08-06-2010 at 05:36 AM.
#3
08-04-2010, 03:47 PM
1augapfel, thanks for your response. I guess I should have started out by telling the whole story... 
A few months back, my Camaro started showing signs of the catalytic converter going bad. It started out as a rattle coming from the cat, which gradually got worse, then went away. There was also increased exhaust noise that was an off and on problem. In recent weeks, the car started driving increasingly bad; it's like it lost all of it's power. Then, last week, while I was driving uphill, things got really bad and I barely made it back home. It kept stalling, when I'd stop, it would be hard to get going again, and when I did get it going, it was running really rough. I figured that the cat had finally given out in a bad way, so I took it to a nearby shop and had them replace it. Unfortunately, when I went to pick it up the next day, I didn't get good news. They told me that my cat was, indeed, shot, and they replaced it for me, but the poor drivability issues still remained. They recommended a shop next door that specializes in GM vehicles, so I dropped it off there and had the guy diagnose the problem. As it turns out, a small plastic vacuum tube that feeds the MAF had melted itself shut, and two of the spark plug wires that are above the cat had also melted. So the bad cat had been running so hot that everything that sits above it that was prone to melting was, in fact, melting.
Now, as for the SES light, I took it back to the shop this morning, and had the guy read the codes for me. These are the codes that it's showing now:
DTC - 75 Digital EGR solenoid #1 circuit error
DTC - 77 Digital EGR solenoid #3 circuit error
The digital EGR valve is also in the area above the cat, so he says the heat from the bad cat probably damaged the insides of the valve. He says it's not that vital to replace, and it shouldn't affect drivability as long as it's not stalling, which it isn't. I'd really like to get the opinion of the "pros" here though... Should I get this EGR valve replaced soon? It doesn't seem to be hard to replace, and I'm sure I could find one at a "pick-a-part" yard.
A few months back, my Camaro started showing signs of the catalytic converter going bad. It started out as a rattle coming from the cat, which gradually got worse, then went away. There was also increased exhaust noise that was an off and on problem. In recent weeks, the car started driving increasingly bad; it's like it lost all of it's power. Then, last week, while I was driving uphill, things got really bad and I barely made it back home. It kept stalling, when I'd stop, it would be hard to get going again, and when I did get it going, it was running really rough. I figured that the cat had finally given out in a bad way, so I took it to a nearby shop and had them replace it. Unfortunately, when I went to pick it up the next day, I didn't get good news. They told me that my cat was, indeed, shot, and they replaced it for me, but the poor drivability issues still remained. They recommended a shop next door that specializes in GM vehicles, so I dropped it off there and had the guy diagnose the problem. As it turns out, a small plastic vacuum tube that feeds the MAF had melted itself shut, and two of the spark plug wires that are above the cat had also melted. So the bad cat had been running so hot that everything that sits above it that was prone to melting was, in fact, melting.
Now, as for the SES light, I took it back to the shop this morning, and had the guy read the codes for me. These are the codes that it's showing now:
DTC - 75 Digital EGR solenoid #1 circuit error
DTC - 77 Digital EGR solenoid #3 circuit error
The digital EGR valve is also in the area above the cat, so he says the heat from the bad cat probably damaged the insides of the valve. He says it's not that vital to replace, and it shouldn't affect drivability as long as it's not stalling, which it isn't. I'd really like to get the opinion of the "pros" here though... Should I get this EGR valve replaced soon? It doesn't seem to be hard to replace, and I'm sure I could find one at a "pick-a-part" yard.
#5
08-05-2010, 04:33 PM
Where to start, where to start, oh my...
The catalytic converter is located under the passenger side floorpan so I'm having a hard timing believing this cooked-underhood-component thing. I mean you're moving forward and the heat from an overheated cat is being carried under the car but, hey, let's go with that for the time being.
I believe (from firsthand experience with an Oldsmobile) that your bad EGR valve *caused* the cat to fail. Sticking EGR valve pintles are bad, very bad, becasue they allow exhaust gases to flow into the intake manifold when they shouldn't. That causes a lean condition in the cylinders that s sensed by the O2 sensors and the computer responds by adding more fuel. The mixture is then rich and the unburned fuel flows back to the cat where it is burned off. And there's too much fuel so the cat gets very, very, very hot. Hot enough to melt the carpeting above the cat and hot enough to melt or soften the ceramic matrix that makes up the cat workng part. And when the ceramic part gets too hot it breaks up and rattles around inside the cat shell, sounding like big bolts in a coffee can. Sound familiar? Now these chunks bounce arouund in there, slowly getting smaller as pieces break off. Eventually they get small enough to move rearward and completely block the cat outlet. I call it constipation. It looks like this:
The catalytic converter is located under the passenger side floorpan so I'm having a hard timing believing this cooked-underhood-component thing. I mean you're moving forward and the heat from an overheated cat is being carried under the car but, hey, let's go with that for the time being.
I believe (from firsthand experience with an Oldsmobile) that your bad EGR valve *caused* the cat to fail. Sticking EGR valve pintles are bad, very bad, becasue they allow exhaust gases to flow into the intake manifold when they shouldn't. That causes a lean condition in the cylinders that s sensed by the O2 sensors and the computer responds by adding more fuel. The mixture is then rich and the unburned fuel flows back to the cat where it is burned off. And there's too much fuel so the cat gets very, very, very hot. Hot enough to melt the carpeting above the cat and hot enough to melt or soften the ceramic matrix that makes up the cat workng part. And when the ceramic part gets too hot it breaks up and rattles around inside the cat shell, sounding like big bolts in a coffee can. Sound familiar? Now these chunks bounce arouund in there, slowly getting smaller as pieces break off. Eventually they get small enough to move rearward and completely block the cat outlet. I call it constipation. It looks like this:
#6
08-05-2010, 04:40 PM
See how the cat matrix has rotated 90 degrees and has assumed the very shape of the cat outlet? Well this "plug" causes an *acute* lack of power. It also causes hard starting. Sound familiar?
Bottom line is that (again) I think your bad EGR valve caused the cat to fail. If you keep running the car as-is the cat will fail again. Get another EGR valve from a junkyard car asap.
As for the melted plastic line "feeding" the MAF, well, there is no such thing. There's a large rubbery tube that leads from the air filter to the MAF but I doubt that failed; it's the air inlet duct. Even if it did all the air entering the engine would still pass through the MAF so it's irrelevant.
Then there's the *aluminum* tube that runs from the RH rocker cover to the rubbery tube. If the aluminum tube melted, well, let's just say that things under the hood got hot. Very, very hot, LOL.
Bottom line is that (again) I think your bad EGR valve caused the cat to fail. If you keep running the car as-is the cat will fail again. Get another EGR valve from a junkyard car asap.
As for the melted plastic line "feeding" the MAF, well, there is no such thing. There's a large rubbery tube that leads from the air filter to the MAF but I doubt that failed; it's the air inlet duct. Even if it did all the air entering the engine would still pass through the MAF so it's irrelevant.
Then there's the *aluminum* tube that runs from the RH rocker cover to the rubbery tube. If the aluminum tube melted, well, let's just say that things under the hood got hot. Very, very hot, LOL.
Last edited by 1augapfel; 08-05-2010 at 04:48 PM.
#7
08-05-2010, 04:40 PM
Thanks again for your insight, 1augapfel. Yes, a lot of that sounds familiar, except for the melting carpet... that never happened. But I guess I should get that EGR valve replaced soon to avoid destroying another cat. Still, I find it strange that the SES light never lit up until after the cat was replaced, but I'll go ahead and get the EGR valve replaced and hopefully everything will be top-notch again. 
#8
08-05-2010, 05:12 PM
As for the melted plastic line feeding the MAF, well, there is no such thing. There's a large rubbery tube that leads from the air filter to the MAF but I doubt that failed. Then there's the *aluminum* tube tht runs from the RH rocker cover to the rubbery tube. If the aluminum tube melted, well, let't just say that thing under the hood got hot. Very, very hot, LOL.
I have the old melted plastic line... if you like, I could post a photo.
Anyway, thanks again for your help... Looks like I'll be taking a trip out to the junkyard tomorrow.
Last edited by wiskow; 08-05-2010 at 05:56 PM.
#9
08-05-2010, 06:09 PM
I did some searching around, and I found this posted on another forum:
Is this accurate? If so, then this could definitely explain the melting vacuum tube and wires...
If the EGR doesn't work on a car that was supposed to have it then the car will have extremely high combustion chamber temperatures causing detonation and the PCM will pull out timing and decrease engine performance. It will also cause increased NOX production which is a by product of excessive combustion chamber heat and will cause your car to possibly over heat and deffinately cause the car to fail any emissions test.
#10
08-05-2010, 10:39 PM
The first 3/4 of the statements are 100% accurate. EGR systems were first installed on 1973 model year cars specifically to knock down combustion chamber temps because oxides of Nitrogen (NO2, NO3) are formed at high temps. If exhaust gases (oxygen poor) don't make it into the combustion chamber (inop EGR) then detonation often results. On a car *with a knock sensor* (most engines from the mid-80s up) that sensor will most definitely recognize it and retard ignition timing to stop it (which will casue a very noticeable drop in power).
As for the last staement, yes, inop EGR will cause high *combustion chamber* temps but I don't agree with the engine overheating statement. Cars were burning high octane gas in high compression engines without EGR systems for decades (like 50s, 60s, early 70s). Did those engine spew vast amounts of NOx? Sure. Did the engines overheat? No. They sure did spew pollutants though.
You have to be careful with broad statements about emissions control devices because they were introduced gradually and, once subsequent devices were introduced, the effect of a faulty component introduced earlier might change.
So EGR systems were around for almost a decade on carbureted engines that had no knock sensors and no oxygen sensor. At certain operating conditions exhaust gases were just dumped into the incoming air-fuel mixture and everybody hoped that the exhaust would be cleaner. Manufacturers bailed on that philosophy when the catalytic converter (1975 or 1976) and then the oxygen sensor (1979, at least in CA) were brought to market.
Suddenly the game changed from screwing with the fuel and ignition systems to clean up the exhaust gases that were leaving the manifolds to tuning for maximum power and then using a converter to clean up what the engine made. A very big (and good) change in drection.
As for the last staement, yes, inop EGR will cause high *combustion chamber* temps but I don't agree with the engine overheating statement. Cars were burning high octane gas in high compression engines without EGR systems for decades (like 50s, 60s, early 70s). Did those engine spew vast amounts of NOx? Sure. Did the engines overheat? No. They sure did spew pollutants though.
You have to be careful with broad statements about emissions control devices because they were introduced gradually and, once subsequent devices were introduced, the effect of a faulty component introduced earlier might change.
So EGR systems were around for almost a decade on carbureted engines that had no knock sensors and no oxygen sensor. At certain operating conditions exhaust gases were just dumped into the incoming air-fuel mixture and everybody hoped that the exhaust would be cleaner. Manufacturers bailed on that philosophy when the catalytic converter (1975 or 1976) and then the oxygen sensor (1979, at least in CA) were brought to market.
Suddenly the game changed from screwing with the fuel and ignition systems to clean up the exhaust gases that were leaving the manifolds to tuning for maximum power and then using a converter to clean up what the engine made. A very big (and good) change in drection.