Hi,
I've recently bought a 1994 ford ranger with a blown 4.0 engine. I bought a new engine and swapped it in. It runs good but the check engine light is on and the code is a 177. After some research I found that this means the engine is running rich. My first thought was it could be the fuel regulator. I pulled the vacuum line on the fuel regulator and no Fuel came out (good thing). I imagine the engine is running just a small amount rich so could the regulator still be just a little broken(not enough to flood the vacuum line but enough to throw a code)? Also the old engine had no EGR system, but the new engine does. it only works if it is wired into the system ( which its not because my wiring harness doesn't have anything for the EGR. I assumed it wouldn't matter because the EGR should remain closed and not affect the engine, but could it? Also if I have a non operational EGR, will I fail smog in California. The trucks from out of state so I would smog it to federal standards. If i put the old exhaust manifold on the new engine and just got rid of the EGR completely, would the engine be exactly the same as a non EGR engine? Thanks,
Jack

 

Welcome to the forum

1994 4.0l didn't need EGR to pass emissions, in 1995 and up it was required
Yes, you can delete it and should before smog testing.
Here's the problem, in Calif you are not allowed to swap in an older engine, must be same year or newer engine, but if you swap in a newer engine then they can require it to meet that new engines model year emissions.............
So you DID NOT SWAP ENGINES, there are no serial numbers on engine that match up with VIN in 1994
You replaced the heads and intake but NOT THE ENGINE


Fuel Pressure regulator can only leak fuel into the engine Via that vacuum hose, so if there was no fuel then it is not the reason for Rich code

177 = Oxygen sensor not switching - system was rich Left bank

Left bank is drivers side of engine, also called Bank 2, Bank 1 is passenger side
Not switching means O2 voltage is high and staying there even if computer lowers fuel flow on the 3 injectors that Bank
Are you blowing blackish smoke out the tail pipe?
You would it it was that Rich
Is the cat converter getting extra HOT, do you hear it popping, you would if its running that Rich

If not then there are TWO O2 sensors one on each bank, so if it hasn't been replaced recently I would replace BOTH O2 sensors
O2 sensors use a chemical reaction, like a battery does, so they do wear out, 125k to 150k miles is when they should be changed, car makers recommend changing at 100k

The old engine "blew"?
That can ruin O2 sensors if they got oil on them or engine was running lean or rich for longer period.

Do you have a history on the "new" engine?

Maybe it has a bad injector on drivers side

Clean the MAF sensor once a year on all 4.0l engine, causes Lean code not rich, but still needs to be done.

 

Your description of the o2 sensors going bad sounds very accurate to whats happening. ill replace those.

The engine I put in is also a 94 so if I understand you right there should be no problem there. however ill still just say the engines the original with new intake and heads. The only other small problem is that the truck stock had a 2.3L engine according the the vin #. the previous owner must have swapped it for a 4.0L, I could be mistaken though. Is there any law about putting a bigger engine in?

Thanks for all your information and help,
Jack

 

Has this Ranger been registered before in Calif?

If so then it will have already been certified, so changing the heads and intake won't matter.

If it has not then it will need to be certified
Read here: https://www.smogtips.com/smog-questi...-in-California

"Only a smog check referee can make the ultimate decision on whether or not a vehicle has had a legal engine change"

 

OK I know its been a wile but I replaced the o2 sensors and im still getting code 177. I tried a lot of "running rich" tests and fixes with no luck. I asked my old auto shop teacher and he seemed to think it was still an o2 sensor problem so we tested them. One was working fine but the other one had a constant voltage running through the signal wire. I looked at the wires and found that on the way up to the rest of the wiring harness, the wires were cut and reconnected using different wire. This was repeated again right before the wires meet with other wires from the harness. I thought maybe the wires were reconnected wrong but from the research I did, they were right. I re did the connections just to make sure. Still no difference. I still think its a wiring problem but im lost as to what to try next. Any ideas. Also if anyone has a 1994 4.0 ranger, could you post a picture of the left bank o2 sensor showing the wire colors and where they go into the plug.
Thanks

 

O2 sensors are Heated and have 4 wires
Heater wiring:
The light blue/ orange stripe wires are the 12volt from fuse #18, key on power
The Black/white stripe wires are the ground for the heaters they run to the computer

Sensor wiring:
Orange wire is on both O2s, it is the sensor reference ground and runs back to computer, it is also spliced with the grey/red stripe wires that run to almost all the other sensors
You can test orange wire with ohm meter to other sensors grey/red wire

Passenger side O2 uses a grey/light blue stripe wire to computer

Drivers side uses a red/black stripe wire to computer

These two wires tell computer which Bank is running rich or lean, so need to be wired to correct side O2 sensor



The O2 sensors themselves have standard wiring but not colors, lol, and use a universal connector

Picture here: https://www.aa1car.com/library/o2_wire_chart.jpg

The Heater wires are usually the same color, Bosch uses two white wires for heater circuit, its a heater so no + and -, as long as it has both it will heat up
Sensor wires are often + and - so they will use two different color wires

O2 sensors generate their own voltage, .1 to .9 volts, so not much, but this is why connections need to be GOOD or you will get false lower readings

1994 4.0l engine wiring below, O2s on 2nd page