Exhaust Smells Rich On Startup, Advice On Things to Check?

[mod5csi]

Good Evening,

1996 LX450 215k miles, 15k old (3 years ago) tune up, factory wires, cap and rotor, NGK platinum plugs, belts, Photoman Alternator Bracket, rebuilt power steering pump, Stock replacement Magnaflow cats and exhaust. Yellr Box calibrated based on GPS speed and math (33" with 4.88). Passed Colorado emissions one year ago, NOx was on the high side.

I, and others have commented, have noticed my exhaust smells rich at startup, especially with cold outside air temps, 25*F. Slightly rich smell at 65*F. No spiking RPMs, steady at 1200 and gradually decreases to 650 as the engine warms. OBD Torque app shows around .8 Gallons Per Hour and gradually decreases to .4 GPH as the engine warms. No increased fuel consumption, averaging around 13.5 MPG (miles traveled/gallons used).

I also have a pinging/exhaust leak/loose timing chain tensioner sound coming from the engine bay during high loads (crawling up a hill at 3000 rpms). Slightly noticeable revving at idle. Detonation is not my first thought as Im at 6000 feet, always run top tier 87 octane, and base timing is about 5* (as I set it several years ago and according to the OBD Torque app).

Now that it is warmed up I have decided to look into it more. Things Im going to check this weekend, please advise on your thoughts:
Spark Plugs, probably just replace them while I am in there
Reset Timing to 3*
Ignition Coil Resistance
Distributor Pickup Coil Resistance and Gaps
Crankshaft Position Sensor (I do have oil seeping from the oil pump seal and front crank seal)
Check the torque on the Crank Pulley Bolt

Thanks,
Doug

 

[elhombre]

The truck should run rich when it is cold because the computer is waiting to see the temperature to come up. When it gets warm enough, the computer will go into closed loop operation and adjust the fuel trim by looking at the O2 sensors. Does it smell rich when you go to the store and turn it off for only a minute or two, then restart it(at normal operating temperature)? I don't know how long it takes the computer to go in to closed loop under this quick on-off cycle, but it can't be more than 10 to 15 seconds.

Engines usually ping at light throttle because it will be on the lean side of fuel trim. Pinging is most likely carbon build up. At least it was for mine.

Gas milage seems good , so it doesn't sound like a real big problem. How long has it been since the air filter has been blown out?

 

[BadReligion]

I think you are fine. CO emissions testing is pretty strict so if something is out of whack you would have failed. Mine always smells rich on startup, especially when its cold out like you mentioned. Why adjust timing from 5* to 3*?

 

[Qball]

That's VERY normal. Even my Prius smells rich on start up.