Rough Idle

[Clyde9]

From: brianjolly  (Original Message)    
Sent: 10/23/2005 3:09 PM

Hi everybody,

Near the end of a 9 hour drive from LA to San Francisco, as I pulled off to fill up on gas my winne coughed and stalled out while I was stopping at the off ramp stop sign. It took a minute to get it started again and the idle was real real rough. I managed to get to a safe spot to stop and let it rest for a while, thinking maybe it needed to cool down, even though the temperature gauge was reading normal during the whole trip.

After a while I decided to give it another go, but the idle was still real rough. If I kept my foot on the accelerator a little to feed it some gas and keep the RPM's up a little it would stay running, and once I was moving everything seemed fine. I made it the rest of the way to SF with little trouble, but every time I had to slow to a stop, I would have to keep a foot on the break, and keep the accelerator pushed in a little with my other foot to keep the engine running.

My only guess was that maybe I got a bad tank of gas during the trip, but after going through a couple tanks, and using a fuel system cleaner and octane boost on the last one, the idle is still real rough, and without keeping a little pressure on the accelerator it stalls out.

Once I'm going it's fine, and I haven't had any trouble going up steep hills, which there are plenty of here.

Anybody have a guess to what my problem might be?

Thanks!
Brian



From: Easybago    
Sent: 10/23/2005 5:18 PM

It would be very helpful to know what you have but it sounds like a vacuum leak could be the culprit. My 78 Dodge 440 did the same thing, so I removed my cruise control and replaced all my vacuum lines and now she purrs like a kitten.

There's some very knowledgeable folks here who can steer you in the right direction. Good luck!

Randy



From: brianjolly    
Sent: 10/23/2005 6:14 PM

Oops, sorry I should have mentioned, it's a 72 Brave with the Dodge 318
engine.


From: denison    
Sent: 10/23/2005 8:11 PM

I doubt it was bad gas, unless you don't have a fuel filter in-line, in which case it could be silt clogging the idle circuits in the carb. If it was water in the float chamber, that would be sucked out with some highway driving.
It could be the secondary carb throat not fully closing. (I presume you have the two barrel Carter carb.) It could be a leak in any vacuum hose, a worn out pcv valve, a leak in one of the hydrovac brake boosters - things that amount to a vacuum leak.
If its the idle circuit that has dirt in it, one trick is to gently screw the idle mixture adjustment in all the way, carefully keeping track of how many turns it takes, then backing it out to where it was when you started. This would hopefully squeeze out any dirt that was in the idle jet space.
It could also be that your points have worn so they are too close together, or are badly pitted. This leads to a very irregular idle sometimes.
And of course check that your centrifugal advance is still free. You should be able to turn the rotor slightly (about 7 degrees) and have it spring back. There is a felt wick under the rotor that should get a drop of oil once a year, and which is the only lube the advance mechanism gets.
And it wouldn't hurt to try a new ignition resistor - that is a part that I would always advise carrying as a spare.
Make sure your carburetor hold down nuts are snug. On some carbs, if the carburetor base gasket is damaged or has gotten sucked in, it will open up passages in the carb that are supposed to be sealed against atmospheric air.
Check one or two of your spark plugs. If they are dark brown or black, it indicates a too rich condition, such as would happen with a carb float that had a leak and was sinking.
And maybe just general loose flakes of dirt in the idle circuits of the carb. If they sit for a long time, the rinsing of use will float loose some big pieces of varnish like deposits.



From: daved27c    
Sent: 10/23/2005 10:17 PM

Brian;

I would recommend changing your fuel filter first. I had a similar thing happen while getting ready to go to the NECWJ. I drove around the conner to the gas station and filled up. I then tried to drive home. If I kept the idle up it would run fine. If I tried to let it idle, it would stall out. The problem was that the bottom of the fuel filter was clogged(with some rusty stuff from the main tank). My 413 only draws enough fuel to fill the bottom of the filter at idle. When revved up it uses all of the filter(another good reason to use the clear filters). While it could be a lot of other things, try the easy thing first.

Dave



From: denison    
Sent: 10/24/2005 7:17 PM

My experience is that even with the fuel filters, there will be rust particles fine enough to make it through the matrix. They end up slowly coating the bottom of the float chamber, but they don’t cause any problems for several years. They are as fine as talcum powder, and are another reason for rebuilding the carburetor every ten years or less.



From: brianjolly    
Sent: 10/24/2005 10:48 PM

Thanks for the tips guys. I'll probably dig into it this weekend. I'll
keep you posted on my progress, or lack there of!



From: brianjolly    
Sent: 11/5/2005 10:36 PM

I though I would fill everybody in the idle problem. On closer inspection of the carb, I noticed an idle screw got bent some how. After I nudged it back into place everything went right back to normal. Now Buster is running nice and smooth!

I can't imagine how this would happen. Too much vibration maybe?

On a side note, some of you might get a kick out of these video's a videographer friend of mine made of my Winne.

http://1mass.com/movies.html

Take a look at "Buster 1st Preview", and "Buster 2nd Preview_Dish".