4Runner running rich?

Joined
Feb 24, 2011
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2,081
Location
California
I have a '91 4Runner that I put a used engine in last year. It runs well. It also got a new cat at the same time as the engine. During high-load conditions, such as going up hills, if I have the back window open, I get that rotten-egg type smell. Therefore, I assume I'm running rich at open throttle conditions. Is this something I can fix?
 
Joined
Apr 23, 2012
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East Mountains, NM
Are you getting a check engine light? If not, you are just smelling the cat doing its thing......Slightly richer mixture is normal at WOT. You might switch fuel brand.......But a better idea is to stop driving with the back window open......that is a good way to get carbon monoxide poisoning.
 
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Jan 10, 2008
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Milwaukee, WI
It's normal at WOT for an OBD car to go into open loop and run rich to keep temperatures down. Perhaps the cat can't keep up, but unless you get a CEL I wouldn't worry too much about it.
 

Stelth

Thread starter
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Feb 24, 2011
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California
Originally Posted By: ARCOgraphite
Make sute the exhaust is super tight ( no leaks) up to the #1 O2 sensor. No misfire?
No misfires, but I'll check the exhaust for sure.
 
Joined
Sep 23, 2007
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Florida
If your truck is so old that the engine had to be replaced, then I am sure the O2 sensor is no longer accurate. Also, sometimes the coolant temperature sensor will fail, but because it fails at a temperature that can happen in normal driving, no error code for coolant temperature is set. Below a certain coolant temperature, the car will run in open loop, and that is why the engine would run excessively rich.
 
Joined
Jan 8, 2006
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Michigan
Originally Posted By: artificialist
If your truck is so old that the engine had to be replaced, then I am sure the O2 sensor is no longer accurate. Also, sometimes the coolant temperature sensor will fail, but because it fails at a temperature that can happen in normal driving, no error code for coolant temperature is set. Below a certain coolant temperature, the car will run in open loop, and that is why the engine would run excessively rich.
spot on for Toyos from those years, I will add the cold weather sensor (??? someone help me here pls), might be bad also leading to rich mix. also, make sure all cylinders are firing
 
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