extreme case of the shakes...

[bigchillcar]

it's got to be partly a cold-running condition problem...

'74 stock cis car...starts right up, but when i drive off, it shakes like crazy. if i give it the right amount of gas, it will stop...let off and it's back...and i mean rough...clunka clunka clunka...makes your passengers laugh it's so extreme.

i recently changed the plugs, the old ones appear like the mixture is fine, could be slightly lean due to a slight whitish appearance...definitely not rich. reset my points gap, dwell right at 38 degrees where it should be. timing? i didn't have the light, but sounded ok, i advanced it a hair. air filter seems still ok and no apparent vacuum leaks. my warm up regulator is disconnected via a broken wire...but it's run fine like that before.

when it's warm, it pulls strongly all the way to redline, but will still shake as i slow almost to a stop.

i think my points may need replacing, maybe 10-15k on them...i see my tach starting to bounce, even with rpm actually steady...this has been a sign in the past of the beginnings of points troubles. anyone see anything here? maybe can't see the forest for the trees...
ryan

[dhoward]

You may have answered your own question. Tach bouncing is indicative of trouble on the low-voltage side of the ignition...
Start with points and grounds...

[bigchillcar]

think it could cause the shaking? i mean, it's rough...it feels like it will shake itself apart unless i give some gas...when it's like this, if i take it to about 4k, it's cutting out really bad...
ryan

[dhoward]

Just my opinion, but I have had some really horrible performance problems that I originally attributed to my Webers. Shaking, misfiring, etc. Changed to a Bosch distributor with an ignitor, and an MSD. Turns out the Webers only needed a mild tweaking to get things up to par. My lesson: Ignition is 50% of the battle....
YMMV...

[Superman]

In the olden days (like, ummmm, 1974), ignition used to be by far and away the number one cause of engine running trouble. Occasionally there might be a fuel delivery problem...usually a fuel pump that went south, or a plugged filter. But ignition systems were the most persnickity of all engine systems, and in those days we used points, condensers, etc. Nowadays, fuel systems are complex enough to compete with ignition systems for the #1 slot.

And whether it's the olden days (like 1974) or now, troubleshooting should begin with an ignition system tune-up. So, you're on the right track with the adjustments you have done. Low voltage signals are likely culprits here, so I'd suggest installing those new points you mentioned. Do the complete ignition system tune-up, as a baseline, before evaluating the fuel system at all.

[dhoward]

Why do you think they call him.....'Superman".

[bigchillcar]

great. i have a new set in my toolbox, guess i'll get after that today. last time they wore out, i had backfiring as well...seems a little different this time, but the cutting out is familiar. wonder why it seems to run fine when warm??
ryan

[vash]

mine shook like a beotch. it was running way lean.

[bigchillcar]

really? my plugs were whitish...as cold as it is now, it would make it a little leaner than in summer too, i'd think. plugs didn't look bad lean, just a little...

your really shook hard, huh? like i described mine? can u give more detail?
ryan

[vash]

like i was trying to drive a standard tranny for the first time. i moved my car from 4000 feet elevation to sealevel. i dont know, but maybe i compounded the problem. i also had backfiring in the intake (another symtom of lean conditions) . the last piece of the puzzle was to take the car to a mechanic to have my airfuel mix checked. he called me back and said it was so lean he was surprised it ran at all. he did his mojo, and told me to come and pick it up. i didnt know crap about airfuel mix, but a few weeks ago there was a thread about a car bucking and one of the smart guys said winter makes a car tend to run lean. my mechanic charged me something like $57 dollars to do it. i asked if he hooked it up to a meter at the tailpipe and he mumbled yes (i think) and said he could even do it by ear. i dont know, it doesnt buck anymore. white plugs are definately an indication of lean conditions, but if cars are anything like motorcycles, they can be decieving. i think plugs indicate conditions that are happening in the cylinder at the point when the car/bike is shutdown. so biker dudes would run the bike at certian RPM's and shutoff and then pull the plugs for diagnoses. keep that in mind.

cliff

[bigchillcar]

trying to understand why things tend to smooth out so well once mine gets warmed up.
ryan

[vash]

ok i am reaching because i am still learning. but here goes; when a CIS car is cold, the WUR lets the car richen up by letting the FD see less system pressure, which in turn lets the air sensor bar move up more easily when the wind blow it up. this in turn pushes up on the plunger at the bottom of the FD that gets the injectors squirting. in this case more fuel (richer). as the car warms up. the warmup reg increases system pressure that restricts the arm and lessens the fuel spray coming from the injectors which effectively leans out the burn. so a warm car can tolerate a leaner mixture. that is why carburated cars choke up when engine is cold and leans out by opening the choke butterfly when warm. i think you should fix that broken wire to the WUR, because i just learned a few days ago that it goes to an electric element that speeds up the warming up of the WUR. do you have that throttle handle between the seats, on your car? do you use it, if so?
i hope my above explanation is correct, if not let the flaming begin.

cliff.

[bigchillcar]

cliff,
thanks for your reply. i understand what you've said, just seeking that added reassurance...sometimes it's easier to troubleshoot others than my own problems!

yeah, the wur acts to lean the mixture gradually as the bimetal strip starts to heat up. initially, the cold start valve provides a rich mixture for cranking up...the wur goes from there...

yep, have the hand throttle...and am somewhat of an expert on it's use! i've replaced/adjusted for a friend and know it's use very well. thanks for your reply...i think i will revisit my mixture on your suggestion. i have the adjustment wrench, i may give it a quarter to half turn and see what i get.
ryan

[vash]

let me know, i am curious too.

cliff

[bigchillcar]

***update*** problem solved!!!

i should have known this...i'm kicking myself. i hadn't changed the points in about 12,000 miles. put in a new set, set points gap to to .305, dwell to 36 degrees (38 + or - 3) and voila! no more severe shaking...nice and smooth.

guess i normally wait for the backfire to remind me to replace them!
ryan

[autoxracer31]

whoops, u fixed it nm on this post

[vash]

right on. i guess superman wins the prize!

[bigchillcar]

yes...sigh...superman does it again.

well, i'm almost there...car is running very well, but noticed tonight my tach needle jumping erratically...points gap may be slightly off, thought i had 'em perfect...either that or my coil wire is loose. i'll check in the am...
ryan

[dhoward]

Good job Superman......