I'm pretty sure I destroyed my catalytic converter.
My throttle cable stuck the other day, and I pulled over to fix it (at the time I didn't know what was happening, but thats a whole other problem). I got back into the car to start it up and forgot to set my kill switch (revelco, actually, but same difference).
After trying to start it too many times, I realized the kill switch was off, and turned it on. The car started fine, but with loads of raw gas in the exhaust, which then proceeded smoke like hell. This smoke died away, everything seemed okay, and I parked the car for the night.
At first I ignored the episode, but when I started it up the next day, it was very reluctant to start, and when it finally started, had that spoiled egg, sulphur smell.
I'm pretty sure the starting problem is because of too much back pressure becuase of the clogged (or slagged) cat. My question is: What should I do? I checked realOEM and they suggest a new cat will cost $2,767.68. I can't afford that, but I also can't afford to not have my car on the road (gotta get my son to daycare).
There seems to be a magnaflow replacement here that is much cheaper, but it looks like more than a bolt in job, and I'm not sure how my mechanic will handle installing the O2 sensor. Also, the car has a Dinan exhaust, so I'm not sure what other modifications would be needed.
Can I get away with driving the car for another week until my mechanic gets back from vacation, or should I park it and get a rental until then?
I'm worried that the increase in backpressure will do something else bad to the car ("OIL PRESS SENSOR - SEE OWNER'S MANUAL" has come up on the OBC once or twice, which is a new problem). Any suggestions?
Hi!
It could be that the cat has clogged, but even more likely that you have smoked the O2 sensor and that could cause your starting problems, does the car go Ok otherwise or does it go roughly?
Aftermarket (highflow?) cat is surely ok, You say its dinan exhaust,it is only cat-back system then if the cat is original?
The oil level sensor varning is precisely what it sounds like, There is a fault in the sensor, not a pressure problem. It sounds like the problem is intermittent so faulty/loose wiring is the most likely cause for that. You need to remove the undertray to get access to the sensor and to check the wiring, easy job.
Sakke
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"You can´t afford cheap things if you´re poor"
The car runs fine and feels 100% normal once started. It just is hard to start; turns over very slowly, then gradually speeds up until it finally fires up. I'm not sure where the Dinan exhaust starts, but I'm hoping it's after the cat. I'll look into the magnaFlow exhaust. Otherwise, do you think it's okay to drive for a few more days? Should I do anything special to try to unclog the cat (if it's not slagged)?
Before you ditch that cat, you might as well get it good and hot and try to burn out that excess gas. It might help reduce some of the clogging. Run it in 3rd gear on the highway at a good speed, then see how she works the next day. Surely check the o2 sensor also, that is much cheaper than a new cat also.
The catalytic converter on the 3.6 constitute 3 ceramic monoliths per substrate housed within each clamshell.
The failure mode for them blocking is usually misfiring underload.
The result is highly elevated exhaust gas temps underload which can cause the upstream Monolith facing the down pipes to either melt & block the gas flow & possibly break up due to increase in pressure & become loose within the substrate & then break up blocking the downstream monoliths.
Results are the same.
With close coupled cats the above plus the potential of raw fuel on the precious metal wash coat of the monoliths can cause failure of the catalisation process due to the fuel breaking down the wash coat but this failure does not impede gas flow.
The catalysts on our cars are underfloor & whilst they are quite slow to light off, they are very durable & impervious to most of the heat & fuel issues that plague close coupled cats bolted on the end of the exhaust manifolds.
I agree with the other guys that you may have a choked oxygen sensor or fouled up plugs...not unheard of especially from a cold start.
A fault code check will reveal all.
I would certainly clean the plugs first & then like suggested, go for a long drive with lots of open roads & get everything nice & hot
If my catalyst has not failed, then how do I explain the intense sulphur smell?
Raw fuel on or within the monoliths not helped by fouled plugs no doubt.
Thats why the suggestion of plug cleaning & a long run will hopefully clear your problem by evaporating all the fuel laden soot deposits.
With some luck the cat will not have recieved long term damage to the wash coat
A fault code check will eliminate the o2 sensor.
Farrell
Last edited by farrell; 3rd January 2007 at 21:16.
This morning, I intentionally ran my car hot, with an additive, on the way to work.
No sulphur smell when I picked up the car tonight! You were right about heating it up.
Thanks for that advice, farrell and dchyde
No engine lights (other than PRESS SENSOR), but I still have a problem with the starter. It turns over so slowly at first that I'm concerned. In any case, I think it'll make it to my mechanic on Monday.
This morning, I intentionally ran my car hot, with an additive, on the way to work.
No sulphur smell when I picked up the car tonight! You were right about heating it up.
Thanks for that advice, farrell and dchyde
No engine lights (other than PRESS SENSOR), but I still have a problem with the starter. It turns over so slowly at first that I'm concerned. In any case, I think it'll make it to my mechanic on Monday.
Glad the smell is gone. These cars certainly like to be driven hard once in a while (or often). Not sure about your starter issue, does it start slow as if you had a low battery or its having issues turning over the crank. Could be related to the oil pressure sensor.
It does start as if I have a low battery. I turn the key, and it sloooowly cranks over (maybe under one crank per second) and then slowly speeds up until it finally fires after about 8-12 cranks of the motor.
Last week one of my door locks stuck overnight (clicking all night), and I had to get a jump in the morning. I fixed it (sprayed WD40 in the door... it was sticky). I've driven the car a bunch since then, so I'm hoping the battery is not the culprit and is charged.
One thing; the PRESS SENSOR code only comes up when I'm turning the car off. It's never there when I start it up.
Another thing; I have a blown center bearing, and seal. Could a loss in gearbox oil be straining the starter (is this a stupid question)? I already have the parts, so I'm getting the center bearing, seal, and transmision mounts replaced next week.
One minor bummer with this center bearing/tranny mount issue: I can't punch it from first gear. The tranny mounts are so bad and the center bearing is shot, so if I do punch it from first gear, the tranny bounces a bit on the underside of the car, and I don't want it to do any damage. After this is fixed, I can drag again! The transmision doesn't bounce after it has some speed; I figure it gets some stability from the drive shaft spinning beyond a certain speed.
Thanks alot for taking the time to help me understand what's going on with my car. I love my M5 (my wife calls it my "other baby") and want to drive it forever!
the O2 sensor and that could cause your starting problems, does the car go Ok otherwise or does it go roughly?
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