MartyMcFly

The thing is broke. Whenever I start my LG4, it runs for like 30 sec then dies. If I unhook it, the car runs fine, but this gives me a code 23 because it is unhooked, and a code 45 for running rich. So I bought a new one. My question is this, if I pry the top of the carb off to replace it, is there anything I need to know so I don't screw it up as I know little about carbs.
Thanx in advance.

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Ludicrous Speed GO!!!

RB83L69

If it works when you first turn the key on, it isn't broken. If the ECM doesn't get pulses from the distributor (from the engine turning) within 20 seconds or so it quits pulsing the MCS until it does get distributor pulses. Take it back to the store, you don't need it.

So what's the real problem? or at least, the symptom? What are you trying to accomplish?

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"So many Mustangs, so little time..."
ICON Motorsports

eightTfourTA

iTrader: (3)

I recently had the same problem; check what RB83L69 said, then check to see if the TPS is reading the proper reference voltage at idle, that's what made my MCS quit after about 30 sec. Thing was, when this was happening my dumb ECM didn't throw me a code. In the tech articles for carbs you'll find instructions for checking the TPS. Are you getting any other codes?

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D.R. Stevens
1984 Trans Am 305HO L69
all the usual external/free mods, original engine
1991 Firebird 305 L03
bone-dead-slow-stock

MartyMcFly

Thanks!
Anyway, here's the whole story: One day I noticed gas leaking from the fuel filter. So I tightened it up. This stopped the leak so I took it out for a test drive. The Check Engine light comes on. So I look for anything that I might have accidentally unplugged. You guessed it, the Mixture Control Solenoid. I hooked it back up and the car would run for 30 sec or so and just die. So I call a mechanic friend of mine who was nice enough to come over and take a look (the guy is a saint). He determines the MCS is broke, and tells me to unhook it for now but get a new one sometime later. I did.

I noticed in another post you said, RB83L69, that if the engine ticks with the key on but engine off, that means the MCS is working, well it did this when my friend was looking at it, but won't do it now.

Also, I couldn't find the section on checking TPS voltage anywhere on this site, do you guys know how? The Haines manual doesn't even say.

eightTfourTA

iTrader: (3)

Oops! Sorry 'bout that, the TPS article I was referring to doesn't specify how to do it on a CC carb. I'll give you my rendition:

Checking the reference voltage: grab your digital voltmeter and make sure it's off from auto-range. Set it to measure a range of 0.4 - 5.0 VDC.
The two wires you'll be playing with are at the middle and the bottom of the TPS plug, probably black(ground) in the middle and blue(ref.voltage)at the bottom.
What I do to check this is stick a small sewing pin into the black wire and another pin into the blue wire. Easier than jumpering the connector.
Now turn your key to 'On' position, and make sure that the plunger for that A/C idle-up solenoid isn't enabled (if it is pull it's plug off for this test) With the throttle closed, measure how much voltage is on that blue wire. Should be around .48-.5VDC.
If it's higher than 1.5V, you'll need to either adjust or replace the TPS.
To adjust you'll need the Thexton tool kit #362 from Napa, or order it online at www.thexton.com. Radio Shack also has a jeweler's tool kit for about $20 that has a tool which can adjust the TPS.
Look at the hinge casting for the pumper arm, you should see a little access plug or a hole (if you're lucky) If the plug is still there, drill a small hole just into it, and start a drywall screw into that hole to pop out the plug.
With your meter connected, adjusting the screw clockwise should bring down the voltage. If your adjustment bottoms out and you're still not getting the right volts, replace the TPS, it's probably toast. If anyone wants to add/subtract/critique this synopsis, go right ahead, it's late & i'm tired so I probably forgot something.
Hope this helps.....zzzzzzzzzz.......

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D.R. Stevens
1984 Trans Am 305HO L69
all the usual external/free mods, original engine
1991 Firebird 305 L03
bone-dead-slow-stock