Hello again, I just posted yesterday with some questions about installing an ignitor II Electronic ignition. Well today I went to change out the points and apparently the previous owner had installed an ignitor I already. I replaced this anyway and the car still has the same issue so I'm assuming it has nothing to do with the ignition. The car runs perfectly, idles great when warm, and revs with no hesitation while in neutral. While driving though, it accelerates great up until about 3100 RPM when the car seems to hesitate and refuses to rev past when the throttle is pushed. A slight bucking can be felt if you pay attention but VERY slight. If you back it off and apply extremely gentle and steady pressure the car does seem to rev past this point slowly though... Any ideas? Has anyone had a similar problem with their car? Timing is set perfectly at 27 BTDC at 3500 RPM.

Note - Car still had original FI, with original distributor (Apart from electronic ignition)

Sounds like a bad TPS board.

https://www.shop.914rubber.com/Porsche-914-...20-914TPS20.htm

That's what I was just reading up on actually. Seems like that could be the culprit... Is there a way to test it before ordering a new one?

yeah, use a Volt/ohm meter to adjust it using Mike Cooley's tech article . I think its still on the Pelican site. Check the traces for extreme wear too

head temp sensor?

Okay thanks, I found the article on Pelican. I'm also reading in a few places that you can unplug the tps to test if this is the issue?

I recently had a a similar problem that was cured instantly with new trigger points. The problem is the pick up points wear down to a point where they no longer work at higher rpms. I'd start with the trigger points.

Okay I'll look into that as well.

Thanks for the input!

Hi,

The trigger points should be checked, there are many threads within 914world that address all of their nuances. Do your search outside with google, the internal search is.......wanting.......

However, trigger points are related to the position of the throttle (pedal) not the RPMs. A very common cruise RPM is on or around 3000-3200. Many people have cured the dreaded Bosche Djet bucking problem with a little turn of the MPS. Many people rally against this.

1. Check the TPS
2. Vacuum - if you have not checked all of the hoses and the Plenum, take off the throttle body, plenum, and headers. Replace ALL gaskets and also pressure check the plenum. mine was very porous.
3. If your MPS has the epoxy missing(check threads here in 914world) quarter-turn counterclockwise (clockwise?) at a time.

For a real trip, take a look at this........

https://oldtimer.tips/en/d-jetronic/56-connector#vw4

Thanks a lot! I'll check the TPS today and let you gus know. Hoping it'll be a simple fix as I've got some other things to look at also.

Heres a little update.

Unplugged the TPS and went for a drive. The car accelerated poorly (as to be expected), but seemed to accelerate through the certain RPM range that was causing me problems.

I took off the TPS and found that the circuit board was very gouged. Almost certain that this was the problem. I took some pictures. A new board should be on the way shortly thanks to 914 Rubber.

And that's your problem for sure!

Hey guys - update here. Installed the new TPS board and tried taking it for a spin. Issue does not appear to be fixed... still hesitates and bucks at around 3200. What would my next troubleshooting step be?

Lube your dizzy weights lately? Needs 1-2 drops of 30 wt in the center hole of your dizzy center shaft annually.

Sticking mechanical advance weights as Jeff Bowlsby says.....grease in the dizzy is 50 years old so it's a hard waxy compound by now

Hmmm okay I'll give that a shot thanks. Also, going back to the TPS for a second, when calibrating it I was not able to get it perfectly at 0 ohm. The closest I could get was about 0.05. I'm assuming this does not make a huge difference?

Can not thank you guys enough. With the new TPS and just a little lube in the advance the car runs perfectly! Thank you.

My 1973 2.0L had the same problem. I replaced the TPS and it now works great. The Board had grooves worked into it deep enough to cause the contact arms to contact at incorrect points on the board.
Watch the YouTube Video on how to change it. It was easy to replace yourself.
Make sure that you have a new throttle body gasket to replace the old one before you take it apart.
While you are at it, change the 7 pin plug boot if it needs to be replaced...do all that at once.
Curuge,
Airdrie CanadaClick to view attachment

Thanks for the response. Already have the new board in and everything is working again as it should. A new board and a little bit of lube on the advance solved the issue.

BTW, this lets you do a custom search of the World. Seems to work pretty well compared to the Search function within the Board itself. I would be hesitant to click on a link such as this, so as an alternative you can search for Google Custom Search and you should find it. https://cse.google.com/cse?cx=0024083458981...772:ajvfxschcgc

Yay!!! Glad to hear it.