Engine miss

[mustube]

I have a miss in my '66 200, I have noticed it at lower rpm's but I have never reved it above 3k. The carb is rebuilt, the plugs and wires are new, as are the points and condenser. Can anybody give me a starting point on how to solve this. I believe I gapped the points at .026, but I don't have a dwell meter to check the dwell. (I actually have a meter but it doesnt work anymore, if anybody knows a way to get it working again please tell me). This is a completely stock engine from air cleaner to oil pan. Thanks for any help y'all could give me.

 

[mugsy]

I had the same problem when I went with a DS-II swap. Found out it was the coil. Anyway......

The miss could be alot of things, so you'll have to isolate it first. I would start by putting a timing light on each spark plug wire while the engine is running. Look at the light and see if the flashes are constant. Next thing is to pull each wire (with the engine off) and test for resistance. The wires of the same length should have the same resistance. If that doesn't work, then re-start the engine and make sure its up to temp so the choke is off. Take a wire off the plug (be careful not to get shocked) one at a time and see how that effects the engine idle. Of course it will run rough with only 5 cylinders running, but you might notice the miss AND the engine running rough. If the engine really doesn't change e.g. still missing, then that is the bad cylinder. You could also check the resistance of the coil, both primary and secondary side. And lastly get some time/miles on the engine and pull each spark plug and inspect. The cleaner spark plug is probably the cylinder that is missing.

After you find which cylinder is the one that's missing (assuming that it the same cylinder all the time), then inspect the cap, rotor, both end of the spark plug (make sure they "click" when they are put on the plug and cap tower) and finally inspect the spark plug for gap/electrode surface condition/etc.

Hope that gets you in the right direction.

tanx,
Mugsy

 

[mustube]

So I took the wires off one at a time, and the first cylinder is the one that seems to be the problem, but the timing light was constant. I switched spark plugs with another cylinder and the problem stayed with the first cylinder, I don't have a meter to check the resistance, but the wires and plugs are all new. I looked at the distributor cap and couldn't see any problems, the new rotor looks good as well. What should be my next course of action?

 

[Junk-Falcon]

dry n then wet comp test

 

[pedal2themetal45]

could be the carb too.

 

[mugsy]

Swap wires out. There shoudl be two wire about the same length as the one to #1. If the problem "goes with the wire" then is new wire time. If not, then I'll have to think about it more......

As Ped2Med45 said, could be the carb too. But let's stick with the ignition side first. Rule all that out, THEN go after the carb.

 

[Bort62]

A miss on a particular cylinder is not likely to be the carb.

Comp check. If you've got a bad valve or something along those lines it would cause what you describe.

 

[Nutz4mystang67]

The plug gap may be too small. The 1971 Chiltons manual says .034 gap.

A gap you have, a slightly rich carb idle circuit will fuel foul a plug quickly if idling too long and not enough hot spark to fire the mixture.

I would open plugs to .035 and turn the mixture screw down 1/8 turn

Also while running at night, mist a spray bottle of water on the plug wires to make sure that the spark is not jumping wire to wire, if so "bad wires you have"

 

[Anonymous]

I had the SAME Problem in My 67 It was the Timing, Yea.. The previous owner had it Retarded almost as far as it would go. Not to mention the car was a Friggen DOG.

 

[Bort62]

He said point gap, not plug gap.

A fouled out plug will follow the plug (and be visible)

His problem stays with the cylinder.

 

[Anonymous]

Compression test. If the same cylinder is weak after changing the wires, you can eliminate the ignition system. Since it only takes air/fuel, ignition and compression for an engine to run, it's either air/fuel or compression. Since only one cylinder is affected, it can't be the carb, which leads back to compression.

Test it dry, once you find the weak cylinder, put a squirt or two of oil in through the spark plug hole, then try again. If it improves, you have a collapsed or broken or weak compression rings. If not, it is in the head.

HTH

 

[mustube]

Well I did the dry compression test and the numbers are as follows...
1: 180
2: 190
3: 193
4: 190
5: 200
6: 190


I don't think the 180 indicates a problem but maybe somebody else would think otherwise. I'll check the electrical system again and do the dry compression test. Occationally a puff of white smoke will come out of the exhaust that corresponds to a miss or rough spot in the idle. Thanks for any help.

 

[Junk-Falcon]

there ok

 

[Junk-Falcon]

there ok