TheSamba.com :: View topic - Rough Running Engine

Sat Nov 08, 2008 4:40 pm

I have an issue with the engine in my 1963 bug and I am turning to you for some help.

The stats – 1915 cc with about 1100 miles on it (built by Jiminez Racing), single Dellorto DRLA dual throat carburetor, points replaced with comp-u-fire.

The problem. The car was running great two weeks ago until I drove it to the trailer to put it away. I had it at my house to change the oil, clean the filter, adjust the valves, etc… I drove it around town for about 25 miles or so after performing the service on it and it ran fine. Then I went to take it to the trailer and after making the 8-mile drive I noticed that something was wrong. Before putting it away it ran fine and the engine sounded normal making it’s usual da da da da da da da da da da da da da da da… After the drive when I let it idle it was making an unusual sound more like duhda duhda duhda duhda duhda. I shut it off and left it for a few minutes and then restarted it. I started up fine but after driving it about 50 feet and stopping it was making the duhda duhda duhda sound again and the idle was very rough as well.

I have started it several times since this first happened and I would always get the same result. It starts fine, idles normally after starting it but then runs rough at idle after it is driven a few feet. Then when starting it again, it starts good but immediately idles rough. If I give it a little gas it starts to pop and it and runs very rough. If more gas is given it runs fine.

I put it in the trailer and brought it back home to try and figure out the problem.
*checked the valves again = set properly
*replaced the spark plugs
*put a new dizzy cap on it
*checked the fuel line = clean/no blockage normal flow
*checked the accelerator pump = worked normal
*checked the timing = used the static timing method per the Muir book and the light came on just before TDC
*hooked it up to another coil = same problem
*Checked compression = #1-119, #2-120, #3-115, #4-125

Then with the motor running I pulled the #3 plug wire = no change, pulled the #4 plug wire = no change, pulled the #1 plug wire = idle slowed slightly and pulled the #2 plug wire and the engine died.

If anyone has any advice please let me know. If you need any more info please let me know. I really want to get it running normally again. Any help is appreciated.

Thanks - Jeremy

Sat Nov 08, 2008 5:30 pm

what does your spark look like?

but if you can pull the plug wires from 3 and 4 and have no change that idle sound is your engine running on 2 cylinders. happens all the time with dual carbs, yours is a single two barrel though so check the idle jets, sounds like the carb might be plugged up somewhere.

Sat Nov 08, 2008 6:11 pm

Thanks runslikeapenguin. I tried the $1.98 tune-up out of the Hibbard book and it seems to have fixed the problem. I drove it around the block a couple times and everything seems normal again :D

Sat Nov 08, 2008 7:45 pm

What kind of carbs are you running ? IDF's maybe ? clean your idle jets...

Ed