gale
06-29-2008, 11:09 AM
So last Sunday I took the wife's m50 for the mandatory bi-annual emissions test. I took it out on the interstate & got it good & hot. It passed the tailpipe emissions but flunked the gas cap vacuum test. Then the b*tch (car) overheated when driving home to swap gas caps from my e32.
I never made it back for a re-test that day but instead, removed the thermostat and waterpump for inspection -- spun the plastic waterpump impeller on the shaft and the thermostat wouldn't open until 12 degrees F hotter than it was supposed to.
AutohausAZ came thru with new parts in short order. Installed a new waterpump with a metal impeller, and new thermostat & aluminum t-stat housing for good measure. Got a new gas cap too.
Back to re-test: gas cap passes, tailpipe emissions flunked, barely passed at high speed, idle failed hydrocarbons -- WTF???
3rd try: New spark plugs, fresh oil change and new air filter, did a "Shogun re-set" (disconnect the DME for 10-15 seconds). Go back to the emissions place for a re-test and this time it passes fine.
The car runs great now, better than it ever has. Temp needle is straight up 12:00 o'clock, idles smooth, has more pull.
Thoughts:
I'm thinking that when it overheated and threw a 1223 DME temp sensor code, that it must have gone open-loop and caused it to fail emissions the 2nd time and clearing the DME fixed that. I took the temp sensor out and it was well within spec at both ends of the temperature range, about 320 ohms at 180F & Bentleys says 270-400 is where is should be.
1. For anyone with a newly acquired m50, check your water pump. The original factory impellers were plastic up until 95 or 96. Throw it away and put a metal one in. Get a cast aluminum thermostat housing while you're at it, to replace the plastic one that will fail one day.
2. Do a "Shogun reset" before getting an emissions test.
3. Keep a spare gas cap in the glove box when getting an emissions test.
I never made it back for a re-test that day but instead, removed the thermostat and waterpump for inspection -- spun the plastic waterpump impeller on the shaft and the thermostat wouldn't open until 12 degrees F hotter than it was supposed to.
AutohausAZ came thru with new parts in short order. Installed a new waterpump with a metal impeller, and new thermostat & aluminum t-stat housing for good measure. Got a new gas cap too.
Back to re-test: gas cap passes, tailpipe emissions flunked, barely passed at high speed, idle failed hydrocarbons -- WTF???
3rd try: New spark plugs, fresh oil change and new air filter, did a "Shogun re-set" (disconnect the DME for 10-15 seconds). Go back to the emissions place for a re-test and this time it passes fine.
The car runs great now, better than it ever has. Temp needle is straight up 12:00 o'clock, idles smooth, has more pull.
Thoughts:
I'm thinking that when it overheated and threw a 1223 DME temp sensor code, that it must have gone open-loop and caused it to fail emissions the 2nd time and clearing the DME fixed that. I took the temp sensor out and it was well within spec at both ends of the temperature range, about 320 ohms at 180F & Bentleys says 270-400 is where is should be.
1. For anyone with a newly acquired m50, check your water pump. The original factory impellers were plastic up until 95 or 96. Throw it away and put a metal one in. Get a cast aluminum thermostat housing while you're at it, to replace the plastic one that will fail one day.
2. Do a "Shogun reset" before getting an emissions test.
3. Keep a spare gas cap in the glove box when getting an emissions test.