i apologize in advance, i'm sure this has been covered thoroughly, but my searches couldn't locate...

i have a jumpy tach & somewhat rough idle, checked battery leads, so i assume it's probably the pickup in the distributor? for some reason, the symptoms improve as the car warms up.

car has a bunch of miles, so i'll probably just replace the whole thing. what is the correct order of ops to replace a distributor? can i just mark the position of the rotor as the old one is removed, set the new one to the same angle and drop it in?

thx- Trace:hail:

 

The jumpy tach could be electrical or it could be the acual idle. Rough idle could be spark related or fuel related, if it's got miles on it then I'd check to make sure the injectors are clean and good.
Also check and reset the IAC and TPS. Both must be good for a good idle.

 

If it improves at it warms up, it may not be the pickup coil. They usually get worse with heat. You may have a moisture problem. Have you pulled the cap to inspect anything yet? Look for moisture.

 

thanks for the help. now it's missing / stumbling when it's cold, but this now gets better once it's warmed up. feels like it just suddenly (and randomly) doesn't fire on one cyl or maybe two together. tach is worse. idle is a better. injectors seem fine.

looked for moisture under dist cap, not wet but fairly corroded... also i don't have an oscilloscope, so how else can you test the pickup coil signal?
thx- Trace

 

and again how do you R/I the distributor if it does need a new one?

 

anyone? are the probs with the tach and missing related?

 

If it's corroded, I'd say get a new one.

And, if you had 2 cylinders fire at the same time....you'd know it

 

new distributor's in, tach is still jumpy, and it's missing WORSE now. i think my timing needs a little tweaking to help the missing, but WTH is causing the jumpy tach?? thanks.

 

IIRC, the 1987 and later HEI systems used a tach filter that was located somewhere outside the distributor. The filter could be a big part of the misfire/jumping tack problems. Anyone know where the newer ones are located?

 

is it just the tach that is jumping or does the engine rev along with the tach? Did you put a new ign module? I amhavingthe same problem with mine but my engine stumbles as well with the tach flickering. my speedo needle jumps too at idle

 

yes, the new dist came with a new module. my engine stumbles too. the speedo does jump a little bit every once in a while, but nothing like the tach.

 

:lala:
i don't really understand why, but i replaced plug wires today and it looks like the problems are gone. thanks everyone for the help.

 

glad to see your problem is taken care of. Take a look at your wires and see if there was any cracks at all in them.

 

one of them had one crack, that's why i replaced them all. i guess one crack is a big deal??

 

I had exactly the same problem last year- did my head in! I replaced the pic-up coil, put in an accell supercoil, changed the plugs and leads and it was fine Problem is I never knew the actual cuplrit. The pickup coil was rusty and the leads were pretty fubared- they tend to go brittle with the underhood temp!

Glad you're sorted though