I just picked up an 84 Z28 w/LG4 engine. I found a light blue wire pulled out of a harness in the engine bay and it's been cut. I traced it to an electrical component on the front top of the quadajet carb. Can someone tell me what this is and why would someone have cut it? I currently have a check engine light with a code 23 and 45 and would like to know if this could be problem. Could there be any harm in splicing this wire back in? I know the carb is computer controlled, buy why would this wire be intentionally cut?

 

Those wires used to end at the diagnostic connector, where you could check the mixture control solenoid dwell.

The way it is now, the MCS is disabled, in the full rich position.

Connect them together and unhook the batt cable to reset the codes, and see what happens.

As to why... who knows why morons cut wires. Because they're morons, I guess.

 

And if any of those codes are related to the ECM coolant temp sensor, then this pigtail (circled in yellow) is known to be the culprit.

 

I reconnected the light blue wire going to the Mixture Control Solenoid. I started the car and it was fine for a minute, the Check Engine Light was off ! After a minute the engine started stumbling, RPM's dropped and it stalled. I guess I know why they cut the wire. Suggestions? Can this solenoid be replaced easily?

 

probably not the solenoid. you should hear it click when the ignition is on and when the engine is running

did reconnecting this wire stop it from clicking or start it clicking?

some sleuthing is in order

 

Should have started the solenoid clicking.

Notice that the color of the wire matches one of the 2 wires (light blue, and pink/black) at the mixture control solenoid, at the front pass side corner of the carb, right above the fuel inlet.

I doubt cutting the wire had any real "purpose". After all, we're talking about HUMANS here. D00d probably thought the green connector was ugly; or, was looking for something that was "hot in run", which that would appear to be after the key has been on for 30 seconds or so, and tried to butcher some aftermarket something or other into it after first butchering that; and it didn't work; so Skillet just abandoned it. Humans are like that: stupid, irrational, illogical, emotional, senseless, self-centered, and otherwise worthless.

Never attribute something to malice (or for that matter, ANY kind of "intent") that can be more easily explained by RAW STUPIDITY. Which, cut up wires like that, are a TEXTBOOK EXAMPLE of.

The stumbling etc. probably has nothing whatsoever to do with the wire. Consider the wire repaired, case closed, and move on. Troubleshoot a stumbling problem independent of that wire.

I would add, looks to me like the coolant temp sensor has already been replaced with the later-model style, including a new pigtail. The original CTS for that car had a sort of "coaxial" looking connector that was a complete turd, and the insulation on the wires to it always crumbled and fell off, leaving the wires bare, which would then short out and give CTS codes in addition to making the car run funny. The newer style like you have now is VASTLY better.

 

It does click like it's supposed to when it's connected and I turn the key. It will start, but like I said, rpm start to drop and it stalls. Runs and drives fine with the wire disconnected. Anything more than that, I wouldn't know what do check next. Probably will take it to the garage.

 

it was once not uncommon for some with a limited understanding of this system to disconnect the solenoid to get the motor to 'run' right. in this case it was disabled.

this effectively causes the system to run 'full rich' which does an excellent job of masking the symptoms from many other problems.

this is a less common 'practice' now because the sample population has shrunk so much in the last 10-15 years.

after ensuring the solenoid is clicking (should click for about a minute with KOEO and continuously while running) I'd first check for vacuum leaks- I like to disconnect and plug every port on the carb and manifold, see if there's a difference. even the pcv. just don't try to drive with the brake booster disconnected.

go from there and post back and we can outline some more sleuthing steps.

 

NO!!!!!!!!!!!

WHATEVER you do, NOT THAT!!! The ONLY way that will make your car run any better, is by means of weight reduction, centered at the owner's wallet.

As naf says, check for the obvious non-technical things, like broken rubber hoses, "Garage" won't even bother with that: they'll just begin immediately emptying your bank account, as quickly as possible if not more, so that they vacuum it all out before you realize that they're playing you for a sucker while pretending to work on it without actually accomplishing anything at all. They'll quote you a carburetor replacement, distributor replacement, any number of engine repairs ("we won't even begin to work on some nasty greasy dirty filthy dripping leaky old POS with 10,000 years of funk all built up all over it like this, first thing we gotta do is 'rebuild' it"), and whatever all else. JUST SAY NO.

Remember: your car is an ANTIQUE. Anybody that ever knew how to work on it "professionally", is either RETIRED or DEAD. They threw out the old test eqpt and special tools (scanners and carb adjusting tools and such) for that system probably 20 or 25 years ago. They are NO BETTER EQUIPPED THAN YOU ARE to work on it, in 2021.

The knowledge of how to fix that system is HERE. It is NOT at "garage". We can help you; but for Bozhye's sake, DON'T TAKE IT TO "SHOP" OR "GARAGE"!!!!!

 

Sofa's post should be a sticky at the top of the tech boards forum !

Sofa and naf are 100% right, someone with just enough knowledge to be dangerous cut that wire to put a band aid on a problem they couldn't figure out. Now your mission is to find and fix the actual problem and not to run it with the wire cut (making it run pig rich and masking the problem). You do know how bad running very rich is for your engine, yes? The whole bit about washing the oil film off of the cylinders and making every 1000 miles of driving be more like 10,000 miles of wear? Lucky for you the guys here who know their stuff are willing to walk you through the diagnosis and repair, WAY cheaper VS that evil "shop" place you were thinking of going to will be.....