my bug's engine shudders at 75 mph...SOLVED

[dino jasper m. morales]

  I'm completely at a loss here...

  My bug's engine shudders at around 75 mph (like its being deprived of fuel). Anywhere lower 75 mph and the shudders disappear. At first I thought it was the carbs (stock solex 31 pct, single barrel) in my stock 1500 engine.  Bought a repair kit for the carbs and had it overhauled by my long time mechanic but the problem still persists. I also suspected my alternator because it's always over charging. I asked around and the common response was too much electricity will also make the engine shudder. To strike out electrical issues, I already bought and installed a new bosch 51 amp. alternator. My voltmeter now reads a constant 14 volts when I'm running with minimal electrical load at day time and around 12.5 to 13 volts during night driving.  I'm already considering to buy a replacement carburator but before I do that, I want to be sure that it's the right thing to do...

[QuickKafer]

If you are sure that the car is not running out of fuel... 

Does it feel like an electrical issue?  How old are your points, rotor, wires, and distributor cap?  At higher RPM the spark can jump around a bit which is essential screwing up your timing.

Scott Faivre

[Yoda]

had a simular problem with my type two 60 mph for a couple of minuets and the engine would cut out till the car slowed to about 30-40 mph and come back to life finally traced it.[when the engine would not start late one night after stopping for chrisps on the way home from the drags with my family and girls had school next morning]   to a faulty petronix ignition unit refitted points can original coil fault gone .Just a thought anyway 
be lucky yoda

[dino jasper m. morales]

If you are sure that the car is not running out of fuel... 

Does it feel like an electrical issue?  How old are your points, rotor, wires, and distributor cap?  At higher RPM the spark can jump around a bit which is essential screwing up your timing.

Scott Faivre

My points, wires are new... (had my engine tuned just last december).  will check on the distributor cap and rotor if it's in good condition.


   Thanks for the advice Scott!

[dino jasper m. morales]

had a simular problem with my type two 60 mph for a couple of minuets and the engine would cut out till the car slowed to about 30-40 mph and come back to life finally traced it.[when the engine would not start late one night after stopping for chrisps on the way home from the drags with my family and girls had school next morning]   to a faulty petronix ignition unit refitted points can original coil fault gone .Just a thought anyway 
be lucky yoda

   Hmmm...I don't have a petronix ignitor installed in my engine yoda.  I'm still using contact points...just had my engine tuned last december. Will tinker with my engine, in the hopes that I find what causes this problem. Thanks Yoda!

[dino jasper m. morales]

already found the problem that causes my engine to shudder at high rpm! The linkage of my carb already has lateral play...the resulting gap causes fuel to drip. That explains why in the high rpm range, it felt like my carb isn't getting enough fuel but in the low rpm ranges the fuel loss due to dripping isn't that significant to starve my carb of fuel and to make my engine shudder! Already bought a new carb and tested if it will still shudder when I reach 75 mph...shudders no more!  Thanks to all those who posted their views on how to solve my problem!

[QuickKafer]

Good News!  I'm glad that you got the problem resolved!  Now you can enjoy your car again. 

Scott Faivre

[dino jasper m. morales]

Now I'm gonna be relaxed  in driving my bug knowing that I already solved my engine/carb problem (and of course knowing that my bug is at its peak performance again is such a big deal for me...) Thanks scott!