TransAm12sec

I was wondering what is involved in when replacing the MCS on a q-jet.

83_1/2 L69

Step 1. Buy a good carb book
Check out Rochester Carburetors (BK-HP14)
http://www.carburetion.com/books.asp

Step 2. Buy a $20 carb core from a junkyard to practice on.
Once you have figured out how to remove and install the "air horn", you'll be ready to safely fix the carb on your car.

I would also rebuild the Acel Pump and replace the Throttle Position sensor at the same time.
http://www.carburetion.com/quadrajet.asp

Have you tested your MCS with an Ohm Meter? Should be 15-25 ohms IIRC.

RB83L69

In all my days, I've never seen a bad one; except for ones where the connector was destroyed by some ham-handed previous work on it. Which is not to say that they can't go bad; only, that it's highly unlikely that there's anything wrong with it.

Why are you proposing to change it out? That is, what is the car doing wrong, that makes you think you need a new one? More than likely, it won't fix whatever really ails the car.

TransAm12sec

The check engine light refers to it, Code 13 is flashing most likely because the mixture is too lean to read, the car gets too warm (close to 220 in 30 degree weather on the freeway, the car does not have overdrive though with 3:73 gears)

My valve covers were leaking oil onto the plug wires causing them to seize, and I replaced the wires, plugs, gaskets, and cap. Now all of the cylinders firing, in place of 6, maybe 6 ½. I don’t know if that has any effect on it, but it worked fine before I changed that.

RB83L69

Turn the key to ON, without starting the engine. Get out and listen to the carb. If you hear it ticking, maybe 7-10 times a second, then it's working. If you don't hear that, check the wiring first; then come back, and we can tell you what to look at next.

The computer isn't smart enough to where the codes mean "replace X part". All they mean, is that whatever input the ECM is receiving from that part, is not what it expects. Other parts can cause the ECM to be extremely confused; and what it will report is just the most seriously inconsistent reading.

Don't go just randomly replacing parts on the basis of "codes". All that will accomplish, is to lighten up the car, by way of the driver's wallet. Figure out what's really wrong before mindlessly parts-swapping.

83_1/2 L69

Code 13 is caused by the O2 sensor being un-pluged! Check out the wire to the sensor. It might have been damaged when you were changing the plugs. Also the O2 sensor might have been "poisoned" by RTV if you used any!

TransAm12sec

If the o2 were unplugged, I would be confused as to why the car is running lean. It would run in open loop mode then wouldn't it?

RB83L69

So, does the MCS tick?

TransAm12sec

I'm in class right now, I'll be able to check in an hour so, and come back to a computer around 9 tonight. I did notice single wire with a weather pack connector dissconnected aound the carb, so that is one issue that may solve all problems, or create new ones.

TransAm12sec

Well, that wire turned out to be for the Oxygen sensor. I got a few burns in the parking lot, but hopefully there are less problems now. Could that problem be related to the comptuer giving me a code for the MCS? When I checked it with a paper clip I remember 2 flashes, followed by three flashes.

TransAm12sec

Well, I have no codes driving, but the car does overheat unless I turn the heater fan on. I still need to check to hear ticking.

83_1/2 L69

On a CCCarb ECM, code 13 is O2 sensor unpluged or bad ECM. That's how I knew your sensor was unplugged. It might mean something else on a newer F.I. ECM.
Pull the neg battery cable to clear the ECM, drive the car for at least 1/2 an hour, then check for codes.
Engine overheating can be caused by many things, not just a lean A:F ratio.