Itinerant Air-Cooled

Hello folks. I have a question for y'all. I was experiencing some lack of power and low to non existent idle with out a little pressure on the pedal at a dead stop. I replaced my points, which were tight and pocked and pitted, I adjusted my valves (all good except #1 exhaust was a little tight - fixed), timing good, but now I am experiencing a tiny bit of Jerky McJerkerson in third gear around 35-40 mph. I checked my temp sensor II and it is well seated and taught (this usually seems to be the culprit) and it has been about a year and a half since I replaced this part (temp sensor II). I was wondering if anyone had any thoughts. I will check all my grounds and what not again, just to make sure. 'Bad Danger' is idle'n smooth and running' much stronger then before, but I don't like the mini-jerk. Thanks everyone.

Kris

Don't go chasing any rabbits without a thorough diagnostic...but...I will say that when my fuel injectors began failing, I had just the slightest jerk in third gear under acceleration (I surmise a torque thing: enough revs in lower gears to bury the dying cylinder). I wrongly assumed it was a fuel filter intermittently clogging, as I had recently removed the tank.

After replacing the fuel filter, the jerking stopped...for about 100 miles, when the injector failed completely in the middle of the Okeefenokee Swamp... Then, symptoms became a bit more clear: top end speed dropped to about 35; fourth gear was no longer an option...then 3rd gear went...ended up limping home in 2nd..doing Lord knows what damage in the process.

For what it's worth, I was running some off-brand "new" injectors with about 700 miles on them. I went back to my 34 year old Bosch, which have worked great.

BUT...there are many, many checks to narrow the problem before launching into parts replacement (and I suck at diagnostics, so I'm basically worthless).

Can you maintain that jerky feeling with the exact right amount of pedal pressure?
If so, can you also avoid it by letting off the throttle a little or pushing down harder to accelerate past it?

Checking FI grounds would certainly be a good place to look. If you didn't have this before your last tuneup, do it all over again and see if it persists. Sometimes if you can't find the problem you can eliminate it by re-doing your work and hoping that one of the systems you touched was the one causing the new problem.

I'd also check for a vacuum leak.

Thanks folks, I'm on it today. I appreciate the feedback.

This is one of the most perplexing problems to track down. Every jerking/bucking situation seems to have it's own unique solution. I tend to think that it is generally some kind of a inconsistent FI voltage issue often due to a bad/weak connection or ground. After years of progressively worsening bucking to the point of no longer being driveable, it came down to a less than clean metal to metal (more like metal to paint) contact of the negative battery strap to the body of the bus inside the engine bay. Once that was cleaned up I have many miles of buck/jerk free driving.

Does it tend to do it more when warm than cold or is it independent of temperature?

Wishing you persistence and good luck.

All tightened up Aopisa! I found a semi-loose ground by my dbl relays and will give the battery strap/ contact another look for good measure. Slow n' steady!

Also, it seems to do this at more of a cold temperature.

I think you're on the correct path...grounds and vacuum leaks are the place to start.