Really hoping you guys can help. Major issue with 67 Mustang

[mustang1967]

This is a 1967 Mustang with 200 Six stock ignition system. It has the correct SCV autolite 1100 and Load-o-matic distributor.

Car has rough idle, dies on deceleration after pop pop sound in mufflers. Runs rough and misses when revved up.

I have had this car for over 10 years so pretty good at the simple stuff. Here is a list of all I have done to rule out the easy fix.

New points, cap, wires, condensor (coil is not old) verified good blue spark at coil wire (off block) and plugs (with spark tester). Has 10 volts at + side of coil when running as it should (ran wire from battery to coil direct anyhow to make sure this is not the issue) .

Triple checked plug firing order. Installed new PCV valve.

Sprayed carb cleaner around hoses, carb etc to check for vacuum leaks. Adjusted points to factory setting with dwell meter. Tried other settings just incase (more gap & less gap).

Verified timing with light. Tried different timing settings by ear. Verifed timing stays constant with light at idle and when revved. Sucked on hose that goes from carb to distibutor changes speed of motor as it should.

Changed fuel filter. Has manual choke that is working properly.

The carb is a recent rebuild and has been running great. I took the top off 3 times to verify and adjust float setting, make sure no crude etc.

I used my vacuum gauge and it is pointing to a problem. Only showing about 13 pounds and this says it is "late ignition Timing" I have used this same gauge on this same car, t'd in the same way and had about 19 or 20 pounds. This is the normal range.

This motor was rebuilt about 20,000 miles ago. I did a compression test a couple years ago when I was having another issue and it was in the 190 range for all cylinders. There is no smoke or engine noise so I doubt it is in the bottom end. This is a weekends only car with not a lot of miles driven.

Head gasket or valves? Not burning oil or loosing coolant. I'm really thinking it is going to be valve adjustment. Does this seem logical? Guess I need to pull valve cover?

Any advice or ideas really appreciated. Will follow advice and post results till fixed. Please help! Thanks a lot in advance.

 

[Asa]

Can you rev it slowly, or does it only die when you floor the pedal quickly?

By slowly, I mean taking half a minute to reach WOT.

 

[mugsy]

What's the point gap/ dwell angle? Check that as well...

 

[mustang1967]

It only dies while driving it on deceleration. Will start back up. Actually it runs pretty good at speed and cruising. This is a 3 speed manual trans. When I downshift before coming to a stop I get the pop pop in mufflers then it will die.

It fires right up with a touch of the key and will idle all day. Just idles bad / rough. It does not have a miss at idle just really bad idle.
Idle seems to get just a little worse when it gets hot. And gets worse if I rev it a bunch and then stop. Car is not overheating at all though.

The choke is manual and off.

If I run it at a higher rev and hold it there it keeps running no problem but starts to miss and I can tell gas is being ignited just a little in the mufflers. Smells like it is running rich. If I rev it real quick it responds well but comes back to crappy idle.

Couldn't help myself and just pulled valve cover to have a quick look. Hoping to see something wrong but looks healthy under there as far as I can tell.

Don't know what to do?

I did confirm TDC points at #1 cylinder. Forgot to mention that above.

I had points at dead on factory dwell setting. Then I messed around with different setting just incase. I also have tried two different sets of points. Both new.

 

[First Fox]

You say you think it is running rich, how do you know? The problem sounds more like a lean condition and a lean mixture will certainly give a ripe exhaust scent. Just trying to keep you from chasing shadows. 8) A piece of dirt making its way past the filter and into the carb makes sense if this just happened out of nowhere,

Did this problem just start, or has it been getting worse over time?

 

[mustang1967]

Thanks for the replies.

I am guessing it is running rich because the plugs were carbon fouled. Could be wrong. New plugs and everything else now.

I wish it was a piece of crude in carb. I have taken the top off three times and made sure it is all good with proper float height, needle valve not sticking and no crud. I tried to lower the float as well to get less gas in the bowl but did not help.

Car was running great for quite a while, then it started to have a rough idle one day, the next time I drove it it started to die on deceleration while driving.

Just figured out the valves aren't really adjustable on the 200 six in 67.

Stumped! Any other ideas much appreciated.

Would a messed up carb cause a Vacuum gauge to say late ignition timing and show low vacuum?

 

[First Fox]

A carb that too lean @ idle will run like crap and give a low vacuum reading. So will a carb that is running too rich. Retarded ignition timing will also cause a poor idle.

Let us deduce...

If it was driving fine one day and ran like crap the next, it is likely that nothing wore out suddenly, IE piston rings or leaky valves). Your balancer may have slipped which would indeed give you a bogus timing reading, but seeing as you tried setting it by ear to no avail, this is not likely. It is not likely that the chain jumped time having 20,00 miles on, but that can happen also. Also I doubt that the distributor moved by its own accord, something may be amiss inside the distributor, but check the easy stuff first.

It may be crud in the carb, but without knowing if it is lean or rich it is only guessing. It doesn't take much dirt to plug a carburetor circuit, and you will not see it by only removing the cover. I was chasing a carb problem once and it had me baffled. I finally removed the carb to take a closer look. Turns a bug had somehow found its way into one of the air bleeds. I dont know, I know I didn't invite him.

Grab some carb cleaner and check for a lean/rich condition as stated above, While your at the parts store, they may gladly loan you a compression tester which will rule out any mechanical problems and its free. Why not? Be sure to introduce a vacuum leak to check for a rich condition. You may have merely blown a powervalve.

If you come up empty handed on those two things, it may be inside the distributor but again, one thing at a time.

We will help you land this plane man.

 

[mustang1967]

Appreciate your help.

Don't think it is distributor because the timing holds steady when looking with light. Timing mark moves and holds steady when revved also. And yes I tried to time by ear incase mark was off but no luck there.

I'm going to rebuild the carb again because it is cheap and pretty easy to do. Hopefully that is the problem. Some mystery crude I can't see?

Will let you know what happens.

If that doesn't work I guess I will have to do a compression test although bottom end should be good.

 

[mugsy]

Just being super-picky here, but gap the points with the block on the highest point on one of the lobes and not necessarily at TDC.

It sounds like you have a good handle on the dizzy though, but the only time I've had the same type of problem (quickly going from good to bad) the problem was in usually found in the dizzy.

A carb rebuild is usually not that big of a deal and always a good idea. Hopefully you'll find something when it's disassembled.

Good luck!

Tanx,
Mugsy

 

[JackFish]

Maybe you got some water in the gas.

 

[Asa]

I just remembered that a faulty PCV valve can cause popping on decel, not sure if it can be connected to the rest though, I don't believe so.

 

[Frankenstang]

I'm going to rebuild the carb again because it is cheap and pretty easy to do. Hopefully that is the problem. Some mystery crude I can't see?

Good luck with your rebuild mustang1967 A couple things to look for when tracking down your flooding issue; tank condition, float condition & type, check balls, fuel pump pressure, etc.

Didn't notice where you mentioned the condition of your fuel tank, but if it's original it's possible you have a fair amount of crud built up in the tank over the years. Besides draining, cleaning and recondition or replacing the tank as necessary, adding an inline fuel filter ahead of the integrated filter (that threads directly into the 1100) can head off the introduction of new crud. The integrated style filter is notoriously porous, letting particles that are too large into the fuel bowl. Fram G2 or some such 'see-through' added inline can help.

IIWIYS I'd be sure to check the float for leaks if it's the original brass type. Bring water in a pot almost to a boil and submerge the float. Heated air inside the float will escape under pressure and you'll see bubbles if you've got a leak. If you're using a nitrophyl (black plastic, foam type float), then they typically require a higher float setting as the nitrophyl "floats" lower than the brass type when wet. Eventually the nitrophyl can break down and allow too much fuel soak, not floating worth a flip.

I'd also suggest making sure all the check balls and the weight are in place, and are the correct size. IIRC there are three required on 1100's with an anti-stall dashpot on the passsenger side of the carb (two required if there's no dashpot...double check me on this against the diagram). Missing or incorrect size check balls can allow for internal fuel bypassing. In particular, not having the weight in place on the discharge side of accelerator pump can cause issues....looks like this, when in place or the second pic of it removed, on one of my 1100's...



In addition, never take your fuel pump pressure for granted. FSD among others here, have reinforced for me that the 1100 can be as picky as the weber's when it comes to too much fuel pump pressure, and the massed produced inexpensive replacement pumps can be all over the map in output pressure

You might also check out Mike's Carburetors site or youtube channel, as he has some handy vids and parts available for the 1100. Good luck
http://www.youtube.com/watch?v=QrvsdDucIXE
http://www.youtube.com/watch?v=eAirfexkMVY