1992 400E, Running erratically at idle.
03-11-2011, 05:42 PM
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2004 SLK 230, 1992 300E & 400E
1992 400E, Running erratically at idle.
1992 400e, 140,000 miles. Took it down to have it inspected, flunked, HC at 279 at idle, passed at 2600rpm.
Just bought the car, drove it from Washington, DC to Dallas, TX, ran just fine. So, I think probably hasn't had a new O2 sensor ever. So, I get a new Bosch sensor and replace it.
Now, when you start it up, it runs just fine for about 5-10 minutes (or until it reaches 80c), then it just craps all over itself. It starts "missing" badly, idle rpm drops to around 350-400, and wants to die when you put it in gear. I can rev it up to a little over 1K and she smooths back out, but, take the foot off the gas and it drops rpm like crazy, almost dying and then back to the 400rpm. What am I missing? HELLLP!
While I was under the car replacing the O2 sensor, I noticed that some yahoo had taken the cats, cut them in two, then brazed them back together. I figure they had a problem with the cats and, instead of shelling out the $600+ to replace them, they just gutted 'em. I have purchased a whole new exhaust system from engine to rear bumper. But, I want to get her running right, first, before subjecting the NEW cats to a fuel-rich condition (I forgot to say: when the bottom falls out, when the rough idle situation occurs then I notice a very ugly exhaust smell, like she is running rich.).
Any help you guys can give me, I appreciate.
Just bought the car, drove it from Washington, DC to Dallas, TX, ran just fine. So, I think probably hasn't had a new O2 sensor ever. So, I get a new Bosch sensor and replace it.
Now, when you start it up, it runs just fine for about 5-10 minutes (or until it reaches 80c), then it just craps all over itself. It starts "missing" badly, idle rpm drops to around 350-400, and wants to die when you put it in gear. I can rev it up to a little over 1K and she smooths back out, but, take the foot off the gas and it drops rpm like crazy, almost dying and then back to the 400rpm. What am I missing? HELLLP!
While I was under the car replacing the O2 sensor, I noticed that some yahoo had taken the cats, cut them in two, then brazed them back together. I figure they had a problem with the cats and, instead of shelling out the $600+ to replace them, they just gutted 'em. I have purchased a whole new exhaust system from engine to rear bumper. But, I want to get her running right, first, before subjecting the NEW cats to a fuel-rich condition (I forgot to say: when the bottom falls out, when the rough idle situation occurs then I notice a very ugly exhaust smell, like she is running rich.).
Any help you guys can give me, I appreciate.
03-12-2011, 08:08 AM
#2
1992 400e, 140,000 miles. Took it down to have it inspected, flunked, HC at 279 at idle, passed at 2600rpm.
Just bought the car, drove it from Washington, DC to Dallas, TX, ran just fine. So, I think probably hasn't had a new O2 sensor ever. So, I get a new Bosch sensor and replace it.
Now, when you start it up, it runs just fine for about 5-10 minutes (or until it reaches 80c), then it just craps all over itself. It starts "missing" badly, idle rpm drops to around 350-400, and wants to die when you put it in gear. I can rev it up to a little over 1K and she smooths back out, but, take the foot off the gas and it drops rpm like crazy, almost dying and then back to the 400rpm. What am I missing? HELLLP!
While I was under the car replacing the O2 sensor, I noticed that some yahoo had taken the cats, cut them in two, then brazed them back together. I figure they had a problem with the cats and, instead of shelling out the $600+ to replace them, they just gutted 'em. I have purchased a whole new exhaust system from engine to rear bumper. But, I want to get her running right, first, before subjecting the NEW cats to a fuel-rich condition (I forgot to say: when the bottom falls out, when the rough idle situation occurs then I notice a very ugly exhaust smell, like she is running rich.).
Any help you guys can give me, I appreciate.
Just bought the car, drove it from Washington, DC to Dallas, TX, ran just fine. So, I think probably hasn't had a new O2 sensor ever. So, I get a new Bosch sensor and replace it.
Now, when you start it up, it runs just fine for about 5-10 minutes (or until it reaches 80c), then it just craps all over itself. It starts "missing" badly, idle rpm drops to around 350-400, and wants to die when you put it in gear. I can rev it up to a little over 1K and she smooths back out, but, take the foot off the gas and it drops rpm like crazy, almost dying and then back to the 400rpm. What am I missing? HELLLP!
While I was under the car replacing the O2 sensor, I noticed that some yahoo had taken the cats, cut them in two, then brazed them back together. I figure they had a problem with the cats and, instead of shelling out the $600+ to replace them, they just gutted 'em. I have purchased a whole new exhaust system from engine to rear bumper. But, I want to get her running right, first, before subjecting the NEW cats to a fuel-rich condition (I forgot to say: when the bottom falls out, when the rough idle situation occurs then I notice a very ugly exhaust smell, like she is running rich.).
Any help you guys can give me, I appreciate.
03-12-2011, 04:55 PM
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2004 SLK 230, 1992 300E & 400E
Does kinda sound like bad cat's doesn't it? What I can't figure out is the "fresh" grinding marks on the circumference of the old cat's, like somebody has just finished a brazing/welding job and was cleaning up the repair. Or, maybe they look so fresh because the cat's are, I guess, stainless steel. Now, that would make sense.........hmmmm.
Maybe it is just the fact that we need some new cat's. Well, howsaboutthat. I just happen to have, voila, new converters laying in my garage, as we speak.
darned pricey little things, aren't they?
Maybe it is just the fact that we need some new cat's. Well, howsaboutthat. I just happen to have, voila, new converters laying in my garage, as we speak.
darned pricey little things, aren't they?
03-12-2011, 10:55 PM
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2004 SLK 230, 1992 300E & 400E
So, I goes out to the garage, puts the monster on the rack and get up under her and take the new 02 sensor out, leaving the mounting hole open. Fired her up, let her warm up, drove around the neighborhood, and no more crappy idle. She didn't run quite as good as I had hoped for, but, for a little bitty hole where the 02 sensor was, and just the little bit of back pressure that was relieved by removing it, I am amazed (also keeping in mind that the 02 sensor is NOT in the exhaust flow, but is, instead, laying on my workbench, which just MAY have a little influence upon the runnin' of things....).
So, I'm just going to take the new FloMaster converter assembly down to my friendly local independent muffler shop, along with a couple hundred dollars and a case of Shiner Bock, and let the young'uns change it out (ya gotta pick yer battles and mine is NOT trying to wrestle the rusted mounting and clamping bolts off that thing whilst laying underneath that behemouth. I didn't get 65 years old by being STUPID!
So, I'm just going to take the new FloMaster converter assembly down to my friendly local independent muffler shop, along with a couple hundred dollars and a case of Shiner Bock, and let the young'uns change it out (ya gotta pick yer battles and mine is NOT trying to wrestle the rusted mounting and clamping bolts off that thing whilst laying underneath that behemouth. I didn't get 65 years old by being STUPID!
05-21-2014, 09:03 PM
#5
Super Member
Larry..I hope you are still on the forum. I have a 400E I got from my sister and my symtoms are very much like yours. Passed the 2500 RPM emmissions test best failed the idle with high HC and CO. Did the replacementm of the cats. fix your problem?
SOLVED !
SOLVED !
Last edited by Brian McL; 06-04-2014 at 11:47 AM.
