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Hi, I have Tim Allen's first Impala "Binford 6100" SS. It only had 54K miles but has decided to run too rich to pass smog. The check engine light had come on a while back during a trip which turned out to be a bad knock sensor. Now there are no codes but the smog test mechanic said the engine would randomly run rough and rich enough to see black smoke from one of the pipes. I've had to get a stock intake system to replace the after market inake that Tim had put on it because it's not certified. It passed the last test with the stock system on it as it had with the custom intake pipe for many years. Could I have put it on wrong? It's pretty simple. Any ideas?
 

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Most likely you have an air leak on the intake. Look for a crack in the rubber elbow on the passenger side of the throttle body, or a vacuum line not connected. The intake pipe might not be properly connected either.

Less likely is an exhaust leak. Even if you can't hear it, sometimes you can feel it by running a gloved hand around the exhaust manifold.
 

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Hi Stonebreaker, the smog tech said air leak too. Coming from carburetor days, an air leak would make it run lean but with all the sensors and computers apparently not. I'll pull it apart and check everything very closely.

Thanks for the tip.
 

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And just fyi this isn't a stock lt1 so the advice given above may not be relevant.

It's the zr1 lt5 which has like dual overhead camshafts on each side and a whole jazz of stuff. Essentially a lotus designed engine. Hagerty has an awesome video on it

Or was that installed in one of the cars and not the other?
 

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And just fyi this isn't a stock lt1 so the advice given above may not be relevant.

It's the zr1 lt5 which has like dual overhead camshafts on each side and a whole jazz of stuff. Essentially a lotus designed engine. Hagerty has an awesome video on it

Or was that installed in one of the cars and not the other?
Tim's first SS was fairly stock. GM built the second one, a 96, with the LT5
 

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Hi Stonebreaker, the smog tech said air leak too. Coming from carburetor days, an air leak would make it run lean but with all the sensors and computers apparently not. I'll pull it apart and check everything very closely.

Thanks for the tip.
The way fuel injection works, if the O2 sensor detects a lean condition, the computer will inject more fuel to compensate. An air leak generally doesn't add air to all the cylinders equally; instead, most of the unmetered air goes into the cylinders nearest to it, and usually on only one side of the motor. So what happens is, when the extra fuel is injected to compensate for the lean condition, the cylinders that were running lean are now normal, but the cylinders that were running normal are now rich.
 
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I'll need to see pictures of this guy with the Binford Car. As of 2020 Tim Allen showed it off in a MotorTrend video. Also, except maybe in CA after 25 years a car is an antique and no longer requires smog testing. I also doubt an intake manifold would fail smog? Again, in CA all things are possible but here in Texas (free state) if it passes the emissions test it passes regardless of what's on the engine.
 
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