Trying to see if someone can help me with a specific issue I am having.

The car is a 1987 Firebird 305 VinH.

Both the mechanical and electric fuel pumps are new.

With the mixture control solenoid plugged in the car will try to start but will not turn over. Also, the MCS makes a loud clicking sound when the key is turned on.

If I disconnect the MCS, the car starts up and runs, I just have to keep my foot on the accelerator to maintain rpms.

Any help is appreciated.

 

Check your ignition timing.

The clicking sound is normal.

 

If it was the timing why would the car start and run with the mcs unplugged?

 

It sounds like your idle circuits are plugged.
Are the anti-tamper caps removed from the idle mixture screws? If so, with the proper tool, turn each screw CW (IN) to count the # of turns each was set at. Just seat them, don't torque them like lug nut! Then remove each. Clean them off with carb cleaner, and also shoot some cleaner in the ports. Reinstall. IIRC, they should each be at least 3 turns out.
While you are at it, clean all the other ports, holes and passages you can see from the top of the airhorn.

 

Your symptoms sound very similar to my car when I first got it. The car wouldn't idle, and needed lots of throttle to keep it running at all. The problem turned out to be the timing wasn't set properly.

'90% of carburettor problems are ignition related'

Make sure the basics are right first before you start to fiddle with your carb. I speak from experience!

 

Thanks for the input.

I'll be sure to check that this weekend.

 

If you can't make the car idle, you may have to go back to first principles and re-check the timing is set up correctly.

Pull spark plug No. 1 and the distributor. Turn engine over to find TDC on No. 1 etc...

Also ensure there are no vacuum leaks.

 

Any chance it it the choke pull off?

 

Is this car new to you? I'd check all vacuum hoses and replace any that look suspicious.

What makes you think it's the choke pull off?

 

Yes, this car is new to me.

I have checked the vacuum lines but noticed that choke pull off does not hold suction.

 

On most Qjets. The primary vacuum break (choke pull off) is not vented and should hold vacuum. If equipped with a secondary vacuum break it is usually vented and vacuum will bleed off.
Joe