Inconsistant Idling

[Corbin83]

Have a 4 barrel rochester on a blue 253, not sure if this is the cause of the problem. My engine has an intermittent problem where the revs will go completely off the chart for no apparent reason. has anyone else had this problem and is there anyone who could point me in the right direction as to how to fix it?

[chris m]

Hi digger,
Let us know , does your car do this under load, when you are driving at a certain speed, taking off or just in park on idle...


respect
chris m

[Corbin83]

More often than not, does it when car is sitting idling. Idles fine until gas is applied, then timing and idle settings seem to change for no apparent reasons. Generally resets after a while but would like to iron out the problem completely. Have car off road with no box so am trying to get everything running properly before putting back on the road.

[chris m]

Hi digger,
Sounds like it could be something electrical.
Your dizzi , open it up and turn the rotor button clock wise not to hard
but until it stops and makes sure it springs back in to its spot.If it springs back this means the shaft is fine. Next i will be checking the vacume advance
unit . look for any cracks in the distributor cap,check leads and change the plugs.....
I hope this helps you a bit,.let us know how you go.


respect chris...

[Corbin83]

Checked dizzie, rotor button returns fine. Also, disconnecting vacuum advance chenges nothing so it if is the dizzy, it's something requireing a full pull-down, I'm thinking. Also thingink it couldbea change in fuel flow through the carby, making it run more fuel through, different butterfly openings, other variants. I rebuilt the carb just over a jear ago but never got a proper chance to check it out for wear so might look at that. Might as well do something while chasing down another box, lol.

[chris m]

Hi digger,
If ya think it could be the carby , try spraying a full can of
carby clean down the carby. (i think i said the word CARBY to many times in
that sentance) but give it a try , you might have a speck of crap blocking
a jet.

ps. .It still sounds electrical cos carbirator problem does not
come and go. .It also could be the modular unit at the back of the distributor. Ppl think when the modular unit goes the car just stops, but that isn't the case it stuffs up the timing and makes the car run what they call retarded, which makes it missfire at different intervals. eg. at 1800 RPM.


Hope that this helps,

Chris

[Cinaed]

Anthoner thing to check is the HT leads on the coil if they are loose you will get the same problem till they shake loose and the engine stops

[Corbin83]

Had thought of modular unit but had been advised that it would just stop, as you said. Will ask a mate if I can borrow a good one off him and check it out. I practically rebuilt mu dizzie about 2 weeks back and thought it had corrected. Started playing up again after about 10 days, lol. Will check that at my next opportunity. Thanx.

[vlv8vic]

mod and coil can both cause intermittant problems ie come and go. i had the saem thing happen on my old carby datsun - turned out that after checking everything mentioned above the harmomic balancer fell off !! it had been loose for a while, occaisionally causing the timing to change enough to screw me around royally. Long shot but make sure its bolted up nice and tight!

[Corbin83]

Hey all, found the problem. The journals on my secondary butterfly shaft was worn as all hell. Occasionally it would shift and let way too much air into the mixture. Replaced the base and runs sweet as now. Thanks for all your help.

[TUF308]

have you checked the adjusting screw on the side of the carby (huge black plastic one), cant remember if this is idle or chocke idle one of the two maybe something simple like that