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Old 08-27-2009
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Join Date: Apr 2009
Location: New Melle, MO
Posts: 3
Need help with several engine codes on '94 4.0L

Hello everyone. I bought a '94 4x4 manual tranny Ranger several months ago pretty cheap because it had clutch problems and needed a new starter motor. I just recently finally got it on the road and it's check engine light comes on after about 5 miles of driving every time. I pulled the codes and the key on engine off test showed code 111 - System pass. But the key on engine on test showed several codes. They were:

176 - Lean bank 2 (something about heated oxy sensor)
172 - Lean bank 1 (something about heated oxy sensor)
136 - lean bank 2
48 - Vane AirFlow is high at idle or injector problem
32 - EGR open / erratic or valve position senson too low

Now before I start throwing money at this, I figured some of these are probably related and there is probably a logical order of things to check/clean/replace. I'd like to hear from anyone who has had these codes and what you had to do to fix it. Looking for expert advice.

I figure I'm probably needing some or all of the following new parts: oxy sensors, possibly a new mass air flow sensor, EGR valve, valve positioning sensor, catalytic converter, ??? I've only put about one tank of gas through it so far, and it doesn't seem to be getting very good mileage. I want to get this thing running good.

As an FYI, it has a 4" suspension lift, 3.73 gears, and I've swapped in a limited slip disk brake rearend from a '98 Explorer. I'm trying to fix this thing up really nice so I'm not afraid to put some money in it, but only if it's necessary.


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Old 08-27-2009
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Join Date: Jun 2006
Location: Wisconsin
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You probaby don't need any of those parts you listed. Sounds like an air leak to me, lean = excessive air not enough fuel. I'd start by searching for a leak in the intake tract.
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Old 08-28-2009
Thread Starter
Join Date: Apr 2009
Location: New Melle, MO
Posts: 3
Thanks for the reply rolsmojave. With fuel injection, would an airleak still cause a lean condition? It seems like it would just allow unfiltered air into the combustion chamber if it's in the air tract. And any leak in a pressurized fuel line would cause fuel to leak out, not let air in. The 176 and 172 codes read lean bank, but also mentioned something in their description about no heated oxy sensor. Since the oxy sensors are responsible for the engine determining how much fuel to pump to the injectors, wouldn't that be the primary suspect for a lean or rich condition?

Also, after driving the truck for awhile, judging by the fumes I'd guess that the truck is actually running way too rich. This would make sense if the oxy sensors are giving a false reading of the engine being lean (and hence throwing the 176 and 172 codes), so it's overcompensating by dumping too much fuel in the cylinders.

Anyone have any more thoughts? I will check for leaks.
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Old 10-28-2009
Thread Starter
Join Date: Apr 2009
Location: New Melle, MO
Posts: 3
Just wanted to update this post. I replaced the oxy sensors and that appears to have been the problem. No more check engine lights and the fuel mileage is much better.
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