Code 23, code 15, code 45 help!!!
 

So I have a 1985 v8 5.0 305 carbureted engine, and I’m pulling these codes. I changed the o2 sensor and the coolant temp sensor to no avail. I did however find that my MIXTURE CONTROL SOLENOID was unplugged, so I plugged it in, and my car is running like ****. Sluggish, and wanting to die out when it’s colder or in general regular driving. What could be causing these codes, is it the mixture control solenoid? Any help would be great. Could it also be the TPS!

Re: Code 23, code 15, code 45 help!!!
 

No it's not the MCS. Probably not the TPS although it could possibly be.

You've already put in a new coolant temp sensor and got rid of the aftermarket p***** track in the water outlet, right? If not, do that next.

OK, now you've got all of the problems you KNOW the car came to you with, taken care of. That's how you deal with these situations: fix everything YOU ALREADY KNOW is broken, then if anything ELSE is wrong, you're prepared to tackle that NEXT, with a clean slate.

Reset all those codes, now that you've fixed the ones you already knew about, by disconnecting the neg batt cable, waiting about 5 minutes, and hooking it back up. Then drive it around for a good while and see which one(s), if any, return.

Meanwhile, there's a simple maintenance item you can do, without worrying about "codes"; odds are, it's a decade or 2 overdue already anyway, and won't be reported by any "codes". Kinda like changing the oil. It's something you just DO from time to time because ... it's a maintenance item.

Have you replaced the fuel filter? Then now's the time.

It's located inside the big nut that the fuel line goes into. Be VERY CAREFUL while doing this, otherwise you risk DESTROYING your fuel line. Please note the emphasis on DESTROY: you can be left with a steaming pile of GARBAGE if you don't follow the instructions carefully.

https://www.thirdgen.org/forums/atta...on-cc-carb.jpg

In this photo, you can see where it says "FILTER" with the arrow pointing to that big nut.

Your fuel line, if still original, will be a plain steel line with a nut, that screws into that BIG nut. You have to break that loose first. To do that, take a 5/8" tubing wrench - NOT an open end, NOT a Crescent, NOT a pair of pliers, a TUBING WRENCH ONLY - and use that on the fuel line nut (corresponding to that blue one in my photo), while holding the BIG nut ABSOLUTELY still with a 1" open end - NOT a Crescent, NOT a pair of pliers, an OPEN END ONLY - to loosen the fuel line nut. The big nut MUST BE HELD STILL and not allowed to turn, because if it does turn while the fuel line nut is still tightened into it, the line will be DESTROYED by twisting itself up into a useless corkscrew. Soak the threads and the inside of the nut where it contacts the line for a day or 2 with penetrating oil such as Kroil or PB Blaster, NOT WD-40; penetrating oil.

https://www.autozone.com/wrenches-pl...nch/914130_0_0

Note how it has all 6 "corners" of the hex, kinda like a socket, as opposed to trying to grab only 2 opposite flats, like an open-end would do.

You can pick up a filter on a card at any parts store. It's a little bitty thing about 1¼" long and ¾" diameter. It goes with the rubber part facing out and the spring behind it. Be very careful to screw the big nut back in by hand ONLY until it's all the way in, as you do NOT want to strip the threads in the carb that it screws into, because that scraps the carb. Put some grease or anti-seize - NOT sealer, NOT Teflon tape, NOT Loctite - on the threads of the fuel line nut and on the end section of the line where the nut sits on it, so that it's easy to get back out next time. Clean up any rust on anything FIRST using one of those small wire brushes about the size of a toothbrush so that it's not fighting you with all its might. Again, screw the line nut into the big nut BY HAND ONLY until it's nearly all the way tight; tighten the big nut first with the 1" wrench, then while holding it still with the wrench, tighten up the other, GENTLY. No need to gorilla any of it.

Do that, see where it takes you, we'll go from there.

Re: Code 23, code 15, code 45 help!!!
 

I changed the fuel filter when I first bought the car maybe 2-3 months ago. Unless the car having the mcs unplugged made it run rich and plugged it again. I unhooked my battery to my car for a minute in the morning. And to no avail, the codes came back. And like I said when I have the MCS plugged in, it turns my check engine lights off, but the codes are still there just with no light, and it runs a little shittier. Any advice for what next?

Re: Code 23, code 15, code 45 help!!!
 

Yes, having the MCS unplugged makes it run STUUUUPID rich.

What the MCS does is, it pulls a pair of tapered rods down into the jets. The tips of the rods are small and they are much larger higher up. The solenoid pulls them down, such that the thicker part of the rod is in the jet, leaning out the mixture. When in the "up" (rest) position the small tips are in the jet, effectively making the jet bigger. The "clicking" is the solenoid doing this about 10 times a second or some such, such that the fraction of the time that the rods spend in each position, determines the "time averaged" jet size. There is also an Idle Air Bleed valve, which provides a bypass for some air to go around the idle restrictions; when closed (down), the idle is leaner. The MCS controls this at the same time as the jets.

Did you clear the codes yet and drive the car to see if they come back? They're gonna stay there for A LONG TIME unless you clear them. Please do what you're being advised to do rather than posting the same things repeatedly so that we don't have to keep saying the same things over and over. Do that, come back, and we'll try to move forward this time.

Re: Code 23, code 15, code 45 help!!!
 

I’ll plug the MCS in, reset the codes by undoing the negative. And get back to you if it changed anything

Re: Code 23, code 15, code 45 help!!!
 

:thumbsup:

Don't forget to drive it around for awhile afterwards and let the ECM have plenty of time to re-acclimate itself to the new conditions, maybe acoupla days' worth depending on how much you use the car, then if the light comes back on, check the codes again.

Re: Code 23, code 15, code 45 help!!!
 

so I plugged in the MCS, and reset codes. Drove it maybe 3 miles or 4. Pushed it hard, let it idle. It got rid of code 23 and code 45 for the rich fuel and other thing. But did not get rid of the code 15 for the coolant temperature. I replaced it but it still shows. Any idea how to possibly fix it?

Re: Code 23, code 15, code 45 help!!!
 

All right, progress! :D

15 is "low temp", i.e. high resistance, i.e. what would happen if the sensor was VERY cold, the plug is disconnected, the wires broken, etc.. The logic is, the coolant temp has very high resistance when cold, and the resistance decreases as it gets hot; and SHOULD reach some moderate resistance value (maybe 2000 ohms or something) corresponding to some reasonable temp or other, don't recall exactly but something like 50°C or some such, within some reasonable time, like 10 minutes. In a properly working engine it'll do that even if it's -40°C ambient. If it doesn't, the ECM concludes that there's this problem. It's all logic and reason.

Measure and report the voltage on the 2 CTS wires with the sensor connected and the car at operating temperature by back-probing the terminals with a sewing needle, taking care not to damage the insulation or seals.

Re: Code 23, code 15, code 45 help!!!
 

and an open circuit at the CTS will cause the ECM to stay in full enrichment mode (cold start) causing the motor to run rich and inefficiently.

I'd suggest replacing all of the spark plugs as soon as everything is resolved.

the wiring for the connector to the CTS can be under a fair amount of stress where it connects. the AIR hoses and some other fiddly bits can bend it back.

if it looks suspect it may be time to just replace the connector. time was you could buy just the pigtail.

many replacement CTS sensors come with a new pigtail, if yours did, just put it on.

Re: Code 23, code 15, code 45 help!!!
 

You still can. No problem. In fact it's the same connector as is used on many newer cars.

Absolutely good advice. Replace whatever you have if it's the slightest bit suspect.

I seem to recall from some one of the photos of this motor that it has the newer connector, spliced on with red butt splices. Butt I could be wrong. Not only merely wRong, butt, mistaken on that one specific point. Once you get a handle on the voltage at the 2 pins, I'd start tracking back from the sensor itself, to see what's broken or whatever. You should have as near 0V (ground) as possible at the black wire, and some voltage probably in the 1.5 - 2V kind of range at the yellow, with the car at operating temp. If they're anything significantly other than that, then it's just a matter of tracking down the broken wire or connection. Easy peasy lemon squeezy. Wiring, or for that matter anything electrical, is about the simplest part of a car to deal with, aside from the fact that it often runs in places that are hard to get to.

Re: Code 23, code 15, code 45 help!!!
 

so I changed the connector. The code didn’t go away. New connector, new sensor. Code still there. Is there any reason besides the wiring is damaged somewhere that the code won’t leave.

Re: Code 23, code 15, code 45 help!!!
 

Nope. That's it.

What are those voltages?

Re: Code 23, code 15, code 45 help!!!
 

Oh... and did you reset the codes after making the repair by disconnecting the batt cable and waiting?

If you don't do that, then whatever codes are in there, will stay there for however many startup / drive / turn off cycles, even if it's all fine now.

As was posted awhile back in the instructions to all this.

You have to do the work, otherwise you won't get the results. Posting on the Internet repeatedly, while not doing what's been explained to you that you have to do, isn't enough all by itself sometimes.

Re: Code 23, code 15, code 45 help!!!
 

I still need to check, could a stuck thermostat cause the code also?

Re: Code 23, code 15, code 45 help!!!
 

Probably not. At least, not if it's above -20° outside or something. I doubt even having no thermostat at all would cool the engine enough to fail to meet the threshold.