Hi all,
I have been battling a engine runnning wrong issue for atleast 6 freakin months now. At this point it's running like it has a massive cam in it. I have rebuilt the carb and dist new spark plugs and wires and have removed all emissions crap. My computer is still hooked up to my carb, but my engine will not run right, it kinda comes and goes, but when it's running alright, I have to move the timing way advanced, past the timing tab and probably twice the length of the timing tab once again just to get it to run right. I don't know what to do but I've run all the simple things like firing order, and such, maybe my computers sucks, but will an engine die when put in reverse if computer's bad? I am worried my timing chanin might have slipped. Any ideas?

Thanks, Dac

 

is your distributer still hooked up to the computer?

 

Yeah, one of my problems I think is that when I removed all my emissions crap, I lost where the hookup on the carb goes, I believe that means that the carb the defaults to running rich, but anyaway I don't have my "blue soleinoid" hooked up. Like shown in the pic. I don't know where it's suppose to hook up too?

 

It will run like crap without the MC solenoid connected.

Didn't cut any wires when removing the emissions stuff? Show us a pic of your engine bay.

Did you set the timing with the ESC plug disconnected from the dist?

 

Let me get you a pic here naf, I realize your busy but I see your online, if you could hold on one sec I'll grab you one.

 

ESC Not disconected but have tried that way and still didn't get any results. Here's a pic:

 

Bump

 

Ok now that I know it's called the mc solenoid I know that I need to hook it up, I just don't know where, and I can't read haynes schematics for sh** so if anyone knows where to hook it to that'd be great!

 

Are the wires there and just cut? They should be in the same harness the wires for the TPS and CTS are from. Polarity shouldn't matter either. Once connected the MCS should click rapidly when the ignition is in 'run' (it'll time out after about a minute if the engine isn't started).

If you set timing to around 0-4 degrees advanced with the ESC disconnected (4-wire plug going to rear of dist), it will run + 20 degrees advanced at idle once it's re-connected, which is probably where you're seeing it.

Re-connect your MCS then get it idling well with the timing where it's happy (ESC connected) then disconnect the ESC and set it properly. Then go through the TPS and dwell adjustments.

This a different motor or still stock?

 

Yes it's stock, I see what you're saying about the timing, I just don't know were my mc hook up goes to. I have the wiring set up but I don't no where to put the end.

 

Not sure what you mean by this. Are you saying you still have all of your computer wiring intact but don't know what wires/plug goes to the MC solenoid? If this is what you're saying then it should be obvious which plug goes to the MC solenoid I would think. I'm not aware of any of the other unused plugs you may have laying around that'll fit other than the correct one.

What 'emmissions crap' have you removed? It's not really a good idea to rip things off your car before knowing what everything is to avoid having problems. You might have accidentally messed something up here.

When you rebuilt the carb, did you set everything up to proper specs ( like the lean stop for example )?

Make sure you reset your timing to proper specs too.

 

When I rebuilt the carb I just followed the directions that came with the kit. I removed everything as fas as emissions, ecm, air pump, carbon canister, as you see in the pic, anything ugly went. Obviously I know that the weather pack end goes into the carb. but my question is, where does the other end go. The end that has the two inch long prongs and is white? If anyone could simply run down their wires on their mcs, and see were it leads, then I would be ready to rock and roll.

 

The MCS connector comes out of the harness that runs along the pass side valve cover coming from the opening near the blower motor. It's part of the wire set that passes through the pass side fenderwell to the ECM. Trace down your TPS or CTS connectors-they come from the same harness.

The longer thin two wire connectors were likely for your AIR, the MCS connector will be shorter.

 

So what your saying is the end that does not hook up to the carb hooks up to the ecm? I don't have enough wire to do so, what I'm wondering is if there is a quick conector that comes out of the wiring harness, that my white two prong hooks to?

Thanks for your time and patience, DacMan

 

Ok so I did just like you said naf, I think I found the connection, and still no results, it runs really choppy. And with or without the dist. hooked up to the comp, it still wants to run the timing way advanced.

 

Ok so here's what I found today naf. I tested my mc solenoid by running the postive and negative leads of the solenoid to the battery terminals and I audibly heard it click. So it works. I also physically whatched my timing advance when I plugged in my ecm to my dist. After setting it. So it works. My question is, I have a group of wires running from my ecm to my drivers side part of the dash. When I was welding in floor pans (stupid me) it caught on fire. (Don't worry the ecm was out when I did this. Anyway many of the wires are quite chared, could it be that some of these wires run to a resistor, that controls the rapid plunging neccesary for my mc solenoid to work properly? Also do I have to have my ecm completly grounded for it to work properly, becuase it's currently laying on my floor pan, with not actual ground from the ecm to a ground, or is the ecm grounded interneally, with a wire that runs into it that provides a ground?

Thanks, Dac

 

Check for vacuum leaks.

When you rebuilt the carb did you reset the lean stop at the same number of turns out that it was originally? Did you verify 1/8" of travel for the MCS plunger? Is the MCS clicking now that you have it hooked up?

You may have to give us a little history here.

 

Never messed with the lean stop till about a week ago, too freakin stupid to count how many turns from all the way down it was. I don't know what to do about that, Never measured the mcs when I rebuilt the carb either, don't really know how. I don't recal having the mcs out. shouldn't have any vaccum leaks b/c I went through and covered all unused holes with "vaccum line covers" MCS is not clicking when I turn the key over, however I use to hear a click when I had the ignition in run and the engine off, but the mcs wasn't even hooked up then. As far as the rebuild goes, it was gaskets, covering the plugs with jb weld, and a new accelerator plunger.

 

Ok, Got home from work and got some possiblities checked off the long list. I spliced all the wires that I have melted together, cutting out all burnt wiring and replacing it with fresh wireing of the same gauge. I already adressed the vaccum leak issue so that's good. My mcs is not clicking when the ignition is turned on? I don't know why, and like said before neither of my clearences were checked.

 

Engine? Year? Stock? Modified?
I can only assume it has a carb. but what kind?
Factory Rochester CCC, a different one ??????????????


Whats a mcs?

 

You removed the ECM? The MC solenoid will not funtion without the ECM. That's what contols it.

I'm honestly totally lost as what it is you're trying to do so I'll let naf field this one since it seems he has a better grasp on what you're doing.

 

I appologize I didn't mean to say I removed my ecm, it is still in tact, the engine is stock, the carb is a stock quadrajet, It is a 1983, 305 CI. I appologize guys, I am not very good at explaining myself through writing, I appreciate the help, any ideas would be fantastic.

Thanks, DacMan

 

Try the attached. It shows the MCS coming off of terminal 18 and common 'C' of the ECM.

I've not used this diagram for an '83 but have found diagrams from this source to be pretty close for other models, just don't trust the wire colors too much-always trace back to the terminals.

You'll need to adjust the height of your MCS (lean stop) inside the carb to get 1/8" of travel for the plunger, measured through the IAB opening with airhorn installed. You can check it by removing the IAB screw and inserting a thin rod. You should be able to feel the plunger click up and down.