1116ft/s

i just got a 04 mach1 with 21 thousand miles on it. on start up it blows out a significant cloud of grey colored smoke. smell like fuel smoke and while it clears right up it continues to smell very rich. the car isnt throwing any cel's and seems very strong on power and still gets good mileage. any ideas about what it could be?

67mustang302

What do the plugs look like?

1116ft/s

i havent pulled them yet, just got the car this morning. the fact the its running so rich and not throwing a cel is really strange to me. and it only smokes is it sits off for an hour or so. but it always smells very rich.

67mustang302

Just cuz it smells rich or is rich doesn't mean the O2 will pick it up. Most people don't know how an O2 actually works, but you can be stupid rich and show normal or even lean. Plugs tell you what's happening in the chamber.

Also wouldn't hurt to check the plug wires as well for resistance.

1116ft/s

its a coil on plug steup, no actual plug wires. how would i check the resistance? and if i pull the plugs and there craped up all that will tell me is what i already know. i know for a fact it is running rich, i just dont know why or how to fix it.

67mustang302

Or you could pull the plugs and they might be wet, or they might look all hot and burnt up. You're smelling unburned fuel in the exhaust tract, which isn't necessarily running rich. You can actually get lean misfires that dump a bunch of partially and unburned fuel into the exhaust system....smells rich, O2 sensor may even detect rich, but it's actually lean. The fact of the matter is you know it has an issue but the ECM hasn't given you an MIL, so it's either not detecting the issue, or not detecting enough of an issue to throw a fault code.

If it's coil on plug then there should be a procedure to check resistance for each coil pack, it's a good idea just to rule it out. All you need is a voltmeter to measure resistance and about 10 minutes worth of time.

Keep in mind that even in the highest levels of racing where the teams are running real time 5 gas monitoring and have some of the most sensitive and sophisticated data logging equipment on Earth, they still check the plugs. You only need to check a few of them to get an idea. If they're all sooty, then you know it's running rich...but if they're not all sooty, then you know that it may be something else, and the 5 minutes you spend pulling a few plugs may save you hours later on down the road of chasing your tail.