Rough idle, with flickering lights!

[Mercury Mike]

For awhile I had my carb/timing set real good. It was running smooth, not trying to get out from under me idling in drive, all that good stuff. Still a bit of a hesitation at take-off but I keep trying to get that acceleration pump into the perfect adjustment.

The problem I've been having recently is that it's been idling real rough unless the idle's really high, and even then I get the occasional thump thump thump out of the engine. Also, when I accelerate in park, it's not very smooth. This is a rebuilt 200 block only maybe 9,000 miles on it, so I guess it's not new new anymore. It goes vrooom thump thump vrooooom thump until higher RPM.

When I first start the car, the oil light is on for about a second and then it goes away real fast. It's been doing that for a long time so I just figured it was building pressure as it started. In idle now, the lights in the cabin flicker with the idle, and it's starting to bug the hell out of me.

I know it's a lot of info but I'm trying to get this engine in top shape. The carb is a rebuilt Autolite 1100, rebuilt it myself. Anyone have any info into any of my problems? Thanks guys.

 

[Lazy JW]

Flickering oil pressure lights worry me a WHOLE bunch First thing I would do is change the oil and filter to a known top quality oil like Chevron Delo 400 15w-40 and a Napa Gold filter. You are in sunny California so don't really need a thin oil and you apparently need something heavier. This really doesn't sound good at only 9000 miles.

Second thing would be to put a mechanical oil pressure gauge to it and verify the actual pressure.
Joe

 

[mkgcars]

Well, the oil light isn't flickering, right, it just comes on initially and then goes off when the pressure builds. That sounds normal.

The flickering interior lights, well, could just be the off idle is throwing off the alt/gen. I'll assume alt. but there were some posts that the gen. didn't do very well at idle - and given that the idle is rough that could effect.

Rough idle could be so many things.
Some quick ideas.

Air/fuel mixture off? (When you rebuilt the carb did you remove the mixture needle - did it have any groove in it? In which case you may want to replace it).

Bad/loose plug wire? -Remove the plugs and see if 1 of them is fouled up. This will tell you to check that wire. Check it with an ohm meter if you have one. Compare it to another wire next to it and see if it's more than a 1-2k higher. If it's similar then make sure it's connected well.

For the heck of it check the dwell.

Recheck the timing to make sure it's where it was.

Check the voltage at the battery (the flickering lights could mean the voltage regulator isn't doing it's job - although I still think thats about the bad idle itself, but could be the other way around)

Check the cap and rotor. Make sure the connection areas look good.

Lets see what the other guys have to offer for advice as well.

 

[Anonymous]

Sounds like it is time for a tune up is all. Oil pressure light sounds fine. Lights flickering at low rough idle sounds find. just need to find the reason for the roughness. standard non computerised fare-- check--cap and button-replace condenser check timing, plugs and wires' also look for clogged fuel filter and possible trash in carb(last two items common at this stage after a rebuild) check PCV and air filter and all vac hoses etc etc etc

 

[CobraSix]

I agree, sounds like you mostly have side effects of poor tuning. My guess is that your idle circuit of the carb may be partially clogged and it can go that fast. I had an idle circuit complete clogged in 10 miles of driving. I dropped my wife off to pick up another car and by the time I got home I had to keep the RPM above 2k to keep the car running. Swapped an old carb I had sitting on the bench and problem solved.

But start simple like mentioned:

1) Check Timing
2) Check your Vacuum at idle
3) Check timing at 2500 RPM
4) Check vacuum at 2500 RPM
5) Check for Vacuum leaks with some carb spray
6) Change your fuel filter
7) Check wires
8) Pull plugs and check gaps

Start with that and see where you end up.

Slade

 

[Mercury Mike]

Can do. I have class today, so I will get it all done tomorrow morning. The timing is at 10*, checked that today. I'll swap the fuel filter. It's got a new condensor as of... 9,000 miles ago, when I put the new engine in. New cap, new wires, new plugs, but old rotor. I'll change the rotor out. Thanks guys. I'll do everything I can get done tomorrow.