Quadrajet sputtering

[Eighty5ov]

Here's a good one:

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I literally just watched this one ha ha

 

[Octane]

Change out your old fuel filter if not done already

 

[Eighty5ov]

Change out your old fuel filter if not done already

Done yesterday.

 

[fast 99]

Is it running on new fuel? It is doubtful the carb would operate correctly if it sat 12 years. However, as others have said you need to get the basics out of the way first. Also check the fuel pressure AND volume.

 

[Eighty5ov]

Is it running on new fuel? It is doubtful the carb would operate correctly if it sat 12 years. However, as others have said you need to get the basics out of the way first. Also check the fuel pressure AND volume.

Has a tank of new fuel. I got a long list I better get my butt cheeks in gear

 

[AuroraGirl]

If he has an original distributor and he also hasnt even checked the timing.... a tune up is in order AND cleaning your advance weights. that alone could be the sputter, but so could a long list already lsisted

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your distributor needs a cap and rotor probably so you can check the coil while transfering it and you can check yoru advance while everything is off, if they look like mine on the above, they are probably sticking

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[Eighty5ov]

Start with the basics. Shut the engine off look down the throat of the carb, operate the throttle butterfly but hand and make sure each side is getting a good shot of fuel off the accelerator pump.

Then check the ignition timing. Set base timing to specification which should be on the underhood sticker. If no sticker is present shoot for 8 - 12BTDC. Check to make sure the vacuum advance is hooked up and functional. Check to make sure the mechanical advance in the distributor is functional, you can do that with the timing light but watching the light and the marks as you rev the engine looking for a total advance of around 30 - 35 or just pop the cap of the distributor and make sure the weights and springs are in place and move freely.

That's the main stuff. How does it run otherwise and how is the idle? When was the last time the carb was rebuilt? Is there a lot of slop in the throttle shaft? Generally throttle shaft looseness will cause other issues to but that or any other vacuum leak like from a rotted or broken hose can cause sputtering but would generally be accompanied by other issues.

When was the last tune up, a plug wiring that only breaks down when your stepping on the gas is technically a misfire but can feel like a sputter to some folks.

Feel free to post underhood pics, but your testing is what will find the problem in the end.

I checked to see if a good shot of fuel was coming from accelerator pump and it was good.

 

[Eighty5ov]

If he has an original distributor and he also hasnt even checked the timing.... a tune up is in order AND cleaning your advance weights. that alone could be the sputter, but so could a long list already lsisted

You must be registered for see images attach

your distributor needs a cap and rotor probably so you can check the coil while transfering it and you can check yoru advance while everything is off, if they look like mine on the above, they are probably sticking

You must be registered for see images attach

I haven’t checked the distributor at all. I’ll investigate.

 

[SirRobyn0]

I checked to see if a good shot of fuel was coming from accelerator pump and it was good.

Well then move on to the next thing. I gave you a good list in post #2, bextreme04 posted a good video on checking timing which you should do and Auroragirl gives good info on the distributor. Now you'll need to investigate the ignition system.

 

[Eighty5ov]

Thanks everyone. I will get to work!

 

[fast 99]

When the cap is apart make sure the ground strap is there. Also look closely at the 2 wires coming out of the pickup coil. Occasionally they will break at the coil and cause the motor to die or misfire.

 

[AuroraGirl]

When the cap is apart make sure the ground strap is there. Also look closely at the 2 wires coming out of the pickup coil. Occasionally they will break at the coil and cause the motor to die or misfire.

if it uses one that style of course. thats a 75 change i think

 

[SirRobyn0]

When the cap is apart make sure the ground strap is there. Also look closely at the 2 wires coming out of the pickup coil. Occasionally they will break at the coil and cause the motor to die or misfire.

if it uses one that style of course. thats a 75 change i think

Yes, that's right the later HEI units did not have that style of ground strap. I'd have to go look up the details on that to get really technical but the main thing is if it has a ground strap it needs to be intact and functional.

 

[Eighty5ov]

So I did some work. I checked timing and it was bang on. Initial and advanced. The distributor advanced and vacuum advance worked. From what I was doing today, it sputtered when it was cold. But once warm I could gas it and was searching for sputter. I don’t know.

 

[SirRobyn0]

So I did some work. I checked timing and it was bang on. Initial and advanced. The distributor advanced and vacuum advance worked. From what I was doing today, it sputtered when it was cold. But once warm I could gas it and was searching for sputter. I don’t know.

Well if it's only sputtering when it's cold maybe it's in the choke. So I guess I need that answered doe it only sputter cold?

If that's the case then we need to be looking at the choke, is it fully closed before cold start up?
It's an 85 so it's got an electric choke which will open up pretty fast, you can adjust it to stay closed a little longer though, how long did it take for the sputtering to disappear after starting it?
Is it running the factory air cleaner housing as is the thermac at least hooked up?
Is the heat riser the weighted mechanical type or vacuum operated, it's probably vacuum given the year. Make sure the vacuum hose is hooked up to the heat riser.
If that's all hooked up we can troubleshoot that stuff, but I had previously thought it was sputtering all the time, not cold only.

Since that wasn't mentioned earlier I had you check the ignition system which wasn't really needed, but on the other hand on an old engine it's good to check the timing anyway.