Now we are chasing the mpg drop w codes 13 and 14, ects and 02 sensor. It's where I would look on a first gen S car anyway, it's rare that it actually throws any OBD1 codes in my experience

 

Ok, about to order the ects, delphi part from rock auto, what coolant should i use? Ugh they designate it by color, and i currently have green in it. But there are a lot of options that are compatible with my vehicle, which would you recommend? Also which spark plugs, will delphi have only one oem part, or are there better options etc?

 

This car only has one oxygen sensor if I recall correctly, OBD1. It should be in the manifold ahead of the flex pipe and not affected by an exhaust leak there. It may just need a new sensor. Try unplugging the sensor and see what happens. The pcm should supply a middle of the road reading and look at all the other sensors. Your coolant sensor is another issue.

 

Andy,
I know that an exhaust leak before the front O2 sensor may cause problems with engine performance due to affecting the reading of the O2 sensor with unmetered fresh air being sucked in and mixed with exhaust gases, thus diluting the oxygen concentration below what the engine is actually producing in the exhaust.

However, can the change in back pressure from a large enough leak near enough downstream of the sensor cause problems with the reading and thus the drivability / fuel mix / etc? Obviously it doesn't change the amount of exhaust generated by the engine, but would it not change the amount of oxygen that the sensor sees per unit time (concentration if you will) if there is less back pressure and the exhaust is flowing more freely (faster as compared to no leak) than normal?

 

I call BS on that coolant listing.

You cannot put dex cool in a first generation S car radiator.

First generation S car cooling systems used the standard green coolant at the time and as far as I am concerned should continue to use the standard green court. Not sure what all this yellow and orange crap is about. They may meet the specifications of the green coolant but I would not want to be dumping a different chemistry into an engine cooling system that was not designed for it.

I will post back with appropriate coolant from that list.

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The plugs are NGK plugs. Don't remember the number, will also post that.
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I'll take a look at the O2 sensor list and recommend what I believe to be appropriate.

Be back soon.

 

You will also want to order the ECTS pigtail connector. I will suggest an appropriate one as well.

 

Okay here we go

Spark plugs. They are now called NGK 7755. Sold in quantities of one so you will need to order 4.

Plugs, order 4

Denso O2 sensor, same as AC Delco listing but half the price.

Denso oxygen sensor

​​​​​​ECTS: Don't know who the f loaded a picture of the first style of ECTS with the resin tip. For this reason I would not buy the Delphi in this case because this may be all they have left in stock. The ancient ones that all fail.

Instead I would order the following


ECTS, just the sensor.

You also want to replace the pigtail connector that attaches to the ECTS. See the following picture.


Replacement connector pigtail for ECTS

Sorting out the coolant mess will take me a bit longer so I'll post that in my next post.

 

Okay. For the antifreeze, as I thought, the proper coolant to use in first generation S cars is the old fashioned ethylene glycol based coolant that usually is green in color. This type of coolant should protect your going system just fine. My suggestion is to pick this up from a store like Napa. Note it is the concentrate and must be deluded with distilled water when it being added to the cooling system.

Do not purchase it online as delivery costs will be insane. The picture of the one below I believe is $12 when you pick it up at the store.

Ethylene glycol based old fashioned green coolant.


Do NOT let anyone convince you that you need anything other than old-fashioned green coolant that is ethylene glycol-based.

Have you tried running the vehicle then disconnecting the ECTS connector. This may help you determine whether the wiring or the ECTS itself is the problem. One of the problems with ordering things from RockAuto is that you need to order a good bit of stuff in order to have the shipping turn out to be not too bad. If it comes out to a ridiculous number, I can help you source parts from other places and figure out what is cheapest that makes sense.
Your preference seems to be to Go for the parts right away. That's fine as long as you acknowledge that the issue could possibly lie in the wiring as I have mentioned previously.

 

We know that the coolant sensors fail and the replacement will fail years from now. I keep two in stock for the two old GM engines we have at work. My experience is that they fail reading cold, -35 degrees. Making the engine run extremely rich to the point of fouling the plugs. I always looked at the data not the code number. I have not jumped the aldl in years and watched flash codes.
On a side note about coolant, I completely agree. I have six or seven different coolants for my fleet based on manufacturer’s recommendations. I do run basic Napa green ethylene glycol and water in the 90’s GM engines.

 

Yes we have ran through the sensor connector problem. Although, the pigtail was never replaced, just rewired.

As a side note: can i sue my old mechanic? He has been licensed and operates out of a shop..