The causes of rich running can be bad Temp II sensor, bad O2 sensor, leaky injectors, throttle position switch not adjusted and perhaps other problems like poorly adjusted air flow meter, etc.
I have never been happy with the connection of the O2 sensor, so I thought I would address that as I hunt for this problem.
The O2 sensor in the 1985 1.9 engine is a single wire type. The multi-wire types are heated so that the signal begins earlier in the warm up phase. The connecting wire is green and is a shielded wire, which means the center wire runs through a tube or sleeve of braided wire which protects the voltage being carried by the center wire from being affected by electric interference. The O2 signal wire sends a very low voltage, like 0.5 to 1.2V signal to the ECU which somehow tells the ignition system to add or subtract fuel.
The test run with a multi-meter at the ECU plug determines if the center wire is grounding out which throws off the message apparently telling the engine to add fuel. You check for continuity between 5 and 7. Seven is a ground on the plug.
Although I passed that test, I was not happy with the connector I used when I put this engine in. Also, I could change the idle by twisting the connection with the engine running.
The connector was a big, clunky coaxial cable connector that I put in without soldering the signal wire to the connector male part and it was not the right size or the right connection. It was just a bad attempt at a connection.
I saw a video of how to splice shielded wire and it looked very simple and clean and frankly pretty obvious so I thought I would give it a try. Of course doing the splice in the engine compartment was a bit more difficult that the video done at an assembly table but I think it worked and here are some picture and a description so that if you choose to do this, you can do a better job. The van is still running rich.
Green shielded wire from the ECU plug
The above picture shows the shielded wire coming from the ECU plug. The copper braided center part of the wire is to the left and is just a normal wire surrounded by green insulation. The other strands of copper are on the outside of the inner insulation and are covered in another layer of green insulation. To strip this wire for the connection, you strip both layers of insulation and the shielding to expose about a half inch of the center signal wire. Then, about an inch back from the signal wire you just exposed, you have to strip the outer insulation only, leaving the braided shielding in place. The shielding is delicate and the outer insulation does not want to strip off easily. Once you have the shielding sleeve exposed, push it back over the outer insulation, away from the exposed signal wire. The inner and outer wires cannot touch. In other words, a shielded wire splice is an inner splice of the signal wire and an outer splice of the braided shielding sleeve.
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| Roll of heat shrink tubing |
Some heat shrink tubing will be helpful to seal up the splices and keep the inner, signal wire from touching the outer shielding sleeve. The same diameter heat shrink will not work on both. So if you have it, use one heat shrink that will work on medium gauge wire and get a larger size that would work on say a TV cable. Remember to slide the heat shrink tube on before you join any of the wires together. You also need to slide on the shielding braided sleeve before you join anything together.
Here is where the shielding braid comes from.
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| The source for the shielding braided sleeve |
I used some coaxial cable from TV installation as the source of the braided shielding sleeve. The picture above shows outer insulation stripped away and the process of cutting the braided sleeve. Going at it with cable cutters will make an even messier braid.
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| Shielding from a piece of coaxial cable to be used to shield over the splice |
Back to prepping the sleeve. To cut it free you strip the outer insulation and then push the sleeve up to make a bulge around where it comes out of the remaining outer insulation. Then you snip the bulge with small clippers. Once it is cut, you can pull the sleeve off. Cutting the sleeve with wire cutters deforms the braid. As you can see with this picture, cutting it with snips also mashes it up a bit.
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| Green shielded wire inner spliced to new signal wire |
The same double, stepped stripping is done to the wire that you are splicing so that you have two exposed inner wires separated from the outer shielding braids and the outer insulation so the inner wires can be kept from connecting with the shielding. I used a crimp connector with heat-shrink as the connector and then another piece of heat shrink to slide over the inner wires. You have to remember to put the heat shrink tube on before connecting the wires.
After the signal wires are crimped together and the connector and the heat shrink are sealed up to insulate the center wires from the shielding sleeve, the shielding sleeve is slid over the splice overlapping with the shielding that was exposed with the stepped stripping. I used small zip ties to hold the sleeve in place before pulling the heat shrink tube over the shielding. Otherwise the heat shrink would have caught on the braids and not passed over the entire splice area. This was the part of the project that was difficult in the engine compartment. I used a heat gun to melt the heat shrink and placed a block of wood behind the splice area to protect other wires in the area from the heat. There is a "C" shaped nozzle that goes on the heat gun which makes a little chamber, like the tube of a breaking wave, to heat the single wire, but I do not have one of those.
Although this did not correct the rich running, this splice is an improvement over what was there before. I am sure that the signal wire is connected from the O2 sensor to the ECU plug and I am sure that the signal wire is not grounding out. I also know that there is some small voltage being generated by the O2 sensor. I only tested with a 10 volt range on an analog meter that I keep in the van and that is not low enough to show the 0.5 to 1.0 voltage ranges and fluctuations that I should be seeing.
I have read that the default message if the O2 sensor is disconnected tells the engine to run on the rich side. So hopefully I am getting a voltage up on the high end which could point me to another cause, like leaky injectors, for the rich running.
