Stalling Out / Occasional Backfire

[Anonymous]

Help!!! My car has suddenly developed a problem with stalling out. It happens in all types of weather and both when the car is hot or cold. The problem started with a little hesitation at steady highway speeds (65 or 70 mph), then the car began to surge followed by either backfiring or stalling out. It does this intermittently. Sometimes I can go for a week without it happening, other times I can not drive more than 5 minutes without it happening. Sometimes when it happens, I can feather the gas pedal, and the engine with come back to life, other times, it will just die.

The specs on the car are as follows:

1965 Ford Mustang with a 1981 200 engine, C4 auto, Duraspark II ignition, with an alternator, 3.2 rear end. I am unsure what carb I have, but it is the original from the donor 81 Mustang six cylinder. The ignition key portion of the ignition switch is new, but not the contact portion (although jiggling the key does not help or hurt the problem).

Thus far, I have tried the following, none of which have worked:

1. Replaced the electronic ignition control box as my car with a new one;
2. Put IsoHeet in the tank, just in case I had water in the gas for some reason;
3. Changed brands of gas and octane levels ( I generally run BP Amoco Silver 89 Octane gas);
4. Changed the fuel filter, it did not appear to be dirty;
5. Checked all ignition wires, plug wires, rotor, distributor cap, coil. All appear to be good. Spark plugs are AC Delcos that have about 8,xxx miles on them;
6. Oil was just changed (but problem began after oil change);

The car will fire right up and idle fine after it stalls out. I can rev the engine and take right off, with no other occurences generally for at least 5 more minutes.

The fuel pump, all fuel lines, gas tank, sending unit were all replaced together about 18 months ago. The timing chain was changed last year when I swapped in the engine. The entire engine

The only four original ignition parts are the coil, ignition switch, plug wires and distributor. All are from the donor 81 Mustang. The carb appears pretty nasty on the outside, but has never given me any other trouble. The car idles fine when it is cold or warm and never overheats.

One persistent problem I have had with this car is poor gas mileage since swapping in the C4, but I figured it was the nature of the beast.

Does anyone have any suggestions regarding what I should check next or what I may have missed?

I have ruled out timing, but am not sure if the coil or fuel pump are going bad. Also curious if I need a carb rebuild as I am not sure of the last work done to it.

Please let me know what you think.

Kurt.

 

[Lazy JW]

You still have the original coil? Get a new one just for general principles. I think you may have a loose connection somewhere in the wiring, maybe a bad ignition switch, or a poor ground. There is no such thing as too much ground! I've had looses wires just give me fits trying to troubleshoot symptoms just like you describe. Good luck!
Joe

 

[CobraSix]

The backfire makes me want to say check for vacuum leaks and your timing.

the stall makes me want to say check your fuel/air mix, and you may have a faulty idle circuit on the carb. How long have you had the carb? It could need a rebuild.

Slade

 

[addo]

Something like a dry joint inside the coil is a possibility. You say the leads are fine. Did you meter them all?

Does the car run hot? What is your compression on a warm engine?

Regards, Adam.

 

[Anonymous]

Well, I found the sources of my problems, and boy am I embarrassed. I went to my mechanic's shop today and spent 5 hours troubleshooting all of the problems listed above. Here are the results of my spending $340 and 5 hours of my time:

(1) It turns out that the splice connections on the duraspark ignition module were not the greatest, which I beleive caused the backfiring. My mechanic also believes the duraspark module may be bad, so we replaced it after fixing the bad connections.

Once this happened, my muffler was bent towards the gas tank, and began touching the fuel line. By the time I discovered this, gas was beginning to pool under the car overnight. We fixed the muffler, rebent the fuel discharge tube on the gas tank, then proceeded to work on the other problems.

(2) Next, I had noticed the car had two distinct noises that I could not explain. The first noise was a clicking noise, while the second was an intermittent knock or rapping sound. The first noise was caused by the new starter that I had ordered from California Mustang. After I compared the new starter to the old one, I discovered that the new starter gear was out approximately 1/4 inch more when at rest than my old starter. Once I replaced the new starter with the old one, the clicking noise went away.

It turns out that the rapping or knocking noise was caused by loose flywheel bolts. I used grade 5 bolts with lock washers as I did not have the original flywheel bolts. I distinctly remember torquing the flywheel bolts to 75 ft lbs, and the lock washers were still flat when we began removing them. The first sign they were lose happened when the 3/8 drive impact wrench freely spun the first bolt off with no effort. We then switch to a 3/8 drive air ratchet, which quickly removed the remaining 5 bolts.

(3) While under the hood, my mechanic noticed that three of the small vacuum lines (one of which runs the choke pull of linkage) were severely rotted. He replaced those, and checked out the powervalve, which appeared to be slow to react to any vacuum. After cleaning the power valve with carb cleaner, it began to move more freely, and was installed back on the carb.

(4) Before letting my car off the lift, my mechanic attempted to show me how to check to see if their are any worn linkage components under my car. He grabbed a hold of the tire, then rocked it from top to bottom. This caused a puzzled look on his face, which was followed by the quick removal of my hubcab and grease cap. He discovered that the previous owner had replaced the proper thin nut and sheetmetal cap with a castelated nut. This prevented the wheelbearings from properly being seated in the hub. No damage was done, he had a spare set of the correct parts and fixed the problem.

Now my car is running much quieter, has greater throttle response, the steering is crisper and my mechanic has something else to rib me about. He constantly teases me about my car, but the apparently loose bolts are a major puzzle for me.

Any clues or words of wisdom from you fellow sixers?

Thanks for letting me ramble.

Kurt.

 

[Anonymous]

Any clues or words of wisdom from you fellow sixers?

Yeah, put a tracking device on that mechanic before I kidnap him and move him to the swamp! I love paying for quality work, I hate trying to find it, and I despise the ignorance that blinds me to both.

I gotta get me some coffee!

 

[x21]

Yeah, mechanics like that are rarer than Mustang concept vehicles from 1963 Glad to hear that all is working out for you too!