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Pythias

Pythias

Jedi Knight
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Since long before LotO, I have considered my car to be cold blooded. It missed a little at low rpms when cold. After it warmed up the problem would usually go away except for a stumble now and then in 4th or 5th gear below 1800 rpms. At LotO, Glen B. was kind enough to tweak the carbs. Minor improvement, no cure.

By the end of last summer it started doing when below 2500 rpms. A couple of weeks ago the engine was all warmed up and it was STILL doing it at almost anything under 4k rpms... ... I checked the timing; off by a few degrees, no help tho. I reset the valves. It sounded smoother but still missed. It always idled fine but under load the miss was there and getting worse. New dizzy cap and rotor... hmmmmmm better. A trip to Portland to see Paul A. and it ran just fine. hmmmm we listened and checked but when i pulled out to go home the problem was back below 2.5k rpm..... Well! A couple of days went by the my new dizzy cap from ADVANCED DISTRIBUTORS with the BRASS contacts instead of aluminum one came along with Jeff's premium rotors. Swapped those in, and took a drive.... YIPPEEEEEEE! ... the only time the engine doesn't purrrrrrrrr is when it RooOO000AAAAARS....

But it was probably that the #2 plug wire kept wanting to fall out of the dizzy(s). I made sure to get it pushed in all the way when i installed the new one(s). ..

Yeah, the problems are usually simple fixes, its just what we have to go thru to finally FIND the problem.
 
I would think #2 wire it was. Vibration got ya.
 
Took a run to Portland. It ran like a top on the way down, but coming home....

It started up without choke and ran fine for about a mile or so, but when I started to get it up to speed on the freeway (about 50, in 5th) it started missing again. Just puttering along, not pressing it. It had a slight miss for about a mile, then I accelerated and the miss went away as it always has a higher rpms. After that it didn't act up one, even tho I ran it at under 2k rpm in 5th, and over 4k rpm in 2nd.... The car has had this low speed miss for way tooo long... .. anybody ... .any ideas?
 
When I got my Sprites, I was ambitious and bought new distributor caps and rotors and wires for everything. It's cheap, so why not?!

Well, things went awry, where the car would run worse and worse, the warmer it got, until I was limping it home in a sputter.

A very long story short, after tons of diagnosis, it turned out to be the cheap rotor from Advance Auto I was using. That whole "can jump a spark through it" problem they talk about with the Jaguar parts.

I am now back to running my original 1960s era stuff and the car runs better.

I have the same stumble you do, but I'm pretty sure it's in the carburetor in my case. I'm still sorting them out.

My problems were as annoying as yours. I'd fiddle with the wires, cap, and rotor, and the car would run perfectly... For a day. Then it'd act up. I'd mess with it again and it'd work fine for a bit and then back to crap.

Ultimately, I'm back to running this rotor:

814378742_4af7ab0db8.jpg


And Accel 3009 solid copper core wires with an old stock cap I got with the car.

813500383_0f3c4c9aa2.jpg


I returned my Advance Auto stuff for the 7 dollars I paid, or whatever. I'm pretty sure the rumor is true about the plastics used containing traces of metal or just a thinner design that allows the spark to ground out to the distributor shaft through the rotor now and again.
 
Sticky valve?

Here's a trick I was shown... take a dollar bill, and hold it right at the tip of the exhaust. Does it just flutter outward? Or does it occasionally suck back inward against the tip? (Indicating that an exhaust valve is staying open on the downward stroke.)

Those little misses can be so irritating, and so hard to find... Practical Classics did a whole two-page spread on diagnosing a miss, about six months ago. Let me know if you'd like it, and I'll see if I can find / scan it.
 
Probably going to the well once too often, but, try swapping out the coil. Bad coils can be frustratingly inconsistent. A bad coil will have you rebuilding you carb daily.

Glen Byrns
 
It's worst when the car is COLD. After it's warmed up, It will all but go away, just a hiccup every once in while below 2k rpm. .... I got the new plug wires today. This will be about the 4th set I've tried. I'm gonna pull the dizzy and blow it out with canned air, and check to see that the shutter is clean and dust free. Give it a nice going over. I'll have to find a spare coil. The one in there is a Pertronix 3 ohm. ..hmmmmm......
 
Bill

If I didn't know your engine didn't have an EGR valve I would swear your EGR valve was sticking open. Is it possible that you have some sort of vacuum leak causing similar symptoms?

Rich Ball
'76 Midget
Everett, WA
 
I have a PCV valve, but not an EGR. hmmmmm.... something else to look at...
 
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