Hi there, you thread watcher you!

I see that you say you have had the same symptoms on your '93 as his '90.

I wrote a post trying to rule out the injectors or ECU stuff. Your post just puts my thoughts in a trashcan. What I am about to write might be worth considering as being too close to a gutter as well!

I am thinking that I have read at least once, that they did away with the cold start injector by '93. Knowing Volvo, it may not be so with ALL models everywhere.

The newest car that I have is a '91. It still has a cold start injector. It is located beneath the manifold so far you would swear it was missing when you compare it to the '86 I own.
I never had this exact issue with my car. I do not live where it gets icy cold. I had an in-law that was in a Minnesota college with an older Datsun 240 Z. He had to unplug the cold start injector in order not flood the engine. I knew I was living in the right place after hearing that!

What you describe, with that wet #3 plug, is a classic leaking cold start problem. Since the newer design has it upside down, it seems strange that it could pool that much gas into one or two cylinders. On the earlier models, the fuel would run down the intake runners into those cylinders.


I would have been suspicious of the signal getting to the ECU from the Engine Coolant Sensor too.
This sensor is farther back than the instrument temperature gauge and can be confusing in that darkness. It can result in a corroded fitting if you live in the salt belt.
I do not know if the wires can be switched or not or if they are even the same at all.

During the open loop mode, cold and warming up engine, either something is out of calibration or mechanically the cylinders are not burning the fuel in your car. Duh, I figured that out.

You singled out the number three cylinder. Without a good compression test, it may be just the weakest cylinder. I can only leave that as; it is how the air flows.
Gasoline is getting there or being left there some how and is my biggest mystery?

Here is where I, like some wires, I may become twisted! You might want to stop reading here. I warned you!

My thought is this harness or umbilical cord down around the engine in itself is something we have to live with.

What IF, the ECS wire became unplugged, broken, pinched or became a grounded circuit wire. The ECU then becomes lost from reality to the engine and one of its many operating conditions. Same thing happens with a 0-2 sensor or AMM problem.

With an open circuit, consequently the resulting very high ohms, the ECU will consider the engine is very cold. A badly grounded, pinched or even a good-grounded wire shows medium low to zero ohms to the ECU. This can mean a possible overheated condition. An open or bad ECS should be blinking that infamous dreaded light of yours but then maybe not. That might have cost another twelve cents more on each car!

These scenarios would engage a preset ECU limp mode map. Either way, it will enrich the mixture. The enrichment method cools the combustion chamber temperatures without shutting off the fuel, which normally would be the best thing to do. However, that would leave someone stranded at speed in the middle of the road. Therefore, it does a limp mode operation.

A cold limp mode scenario still might be richer than actually is needed. I will then throw in a used engine with compression detuning. Even more reason for good sensor outputs.

Under a new cold start up, the 0-2 sensor, that is not warm yet, will be outputting a zero voltage signal. The ECU is now missing another perimeter before going into the warm up map. The ECU will stay richer until the 0-2 sensor warms up and takes the ECU off one side of that cold map. The engine then goes leaner with the varying voltage, like in a normal warm up mode operation map and smoothes out a little better. Where the closed loop mode tunes the engine with a questionable ECS setting, is a guess.

Overall gas mileage can suffer. The oil could get dirtier sooner and the plugs can have a strange color for various reasons. Like incomplete combustion of those oil and gas enhancement additives during driving modes.

You might want to check the ECS by back probing a pin at the ECU and compare it to a chart for the proper resistance at different given temperatures. Unplug and recheck the circuit to make sure it is the right connector. Schematics and colors to the eyes vary some, for all people, let alone the model of car.

Spray all ECU component connectors with T.V. tuner cleaner if you can find something very light like that anymore. I use LPS, #1 or #2 lightly and “Q” tips are good. Stay away from the old WD 40 fragrant kerosene. You do not want that to get into or onto any circuit boards.

Auto electric shops/stores sell a light corrosion resistant gel in a tube that I have had good results with lights and heavier things on my cars.

I suggest checking all the plugs, soon after shut down. Then put them back loosely until morning and recheck. You could pull the injectors and tightly rubber band wrap them tightly in gas resistant plastic overnight but that will leave the intake open to dry out, scratching the cold start test, if it has one. Otherwise, check the insides of the intake manifold for any raw gasoline the next day from any one of the four or the cold start injector. If nothing this time, jump the pumps on from the fuse panel. Then do the sniff and look routine with determination!

I have run out of my fuzzy logic mode for now.
By the way, how is the mileage doing in this car?

Phil