Djet Speed Transition Issues

[hambone]

Drove the '72 Squareback to the paint shop today, first time up to a decent speed in 15 years or so. Cold and nerve wracking without windows! But she got there happily.

Once up to higher RPMs, the engine has plenty of power and speed. From idle to mid RPMs however, there seems to be a lack of power and a lurching, which goes away once RPMS get up there again. Crusing thru the neighborhood at 20 mph without giving it much gas causes the lurching.
I know temp sensor II is bad. It is timed correctly as far as I know. It was advancing properly as well.

Any help would be greatly appreciated! Not sure where to start on this one. Bad distributor? Bump up the fuel pressure a tad?
I will have the car back later in the week so I can't do anything until then.

[Bleyseng]

Temp 2 sensor going bad means too rich a mix so at partload the engine is flooded with gas. At higher rpms the engine can catch up to the extra fuel.
Check that dizzy as low power at low revs is usually a timing advance issue.

[Amskeptic]

Drove the '72 Squareback to the paint shop today, first time up to a decent speed in 15 years or so. Cold and nerve wracking without windows! But she got there happily.

Crusing thru the neighborhood at 20 mph without giving it much gas causes the lurching.
I know temp sensor II is bad.

Nerve-wracking without windows? Boy, you ain't tried it without any door latches ... oh wait a minute, yes you have ...

We know that your distributor is happy, remember how your centrifugal advance was getting involved just above idle? Ensure that the temp sensors fall within specifications before fooling with the mixture, and stay away from the pressure regulator adjustment until all else is lost. The manifold sensor is adjustable as a last last resort. Best to have a LM-1 to help you map the mixture from low to high speed and loads. You can check out the early Porsche 914 forums for the advanced manifold sensor tweaks. I like the idea of a potentiometer in the head sensor circuit as a trim adjustment from the driver's seat. Ask Hippiewannabe about his.
Colin

[hambone]

Replaced TS1, TS2 disconnected. It is still lurching at low RPMs. Once the revs get up it seems to run fine.
I checked part #s, except for a missing sticker on the ECU they are all from the same year (pressure sensor, throttle positioner, temp sensors).
Could a long-dormant engine just need "breaking in"?
I am thinking this car needs to be checked with someone who has the proper test equipment. I've done about all I can at this point.

[Bleyseng]

Test the TS2 with a ohm meter...it won't run right with it disconnected.

[hambone]

I was told that with Djet, TSII isn't very important? I dunno.
It has a strange symptom: running fine at idle, then after pushing and holding the accelerator pedal down to a certain point, the RPMs drop after a couple seconds, even though the pedal position stays the same. You have to rev it again to get the RPMs up. This MUST correspond to the low-RPM lurch.
The tailpipe is completely soot-free. It seems like it's running too lean but that's just a hunch.
Would the throttle positioner have anything to do with these issues?

I think I have to post my problems on Samba, they have a very big Type3 contingent.

[Bleyseng]

The TS11 or CHT tells the brain the temp of the head so when cold the brain enrichens the mix for startup and cold running. It has a ohm range from cold to hot to tell the brain how much to change the basic mix.
The Throttle position switch tells the brain if the engine is at idle, part load and WOT. It must be adjusted correctly or the engine will run goofy with poor transition.
Lean running usually is a bucking/missing that prevents decent acceleration. Have you tested the injectors to see if all four spray correctly? Use baby food jars and pull the coil wire so there's no spark and test em looking at the spray pattern.

[hambone]

It must be adjusted correctly or the engine will run goofy with poor transition.

See, I think this may be a problem. Colin and I attempted to adjust the throttle positioner but it wouldn't click like it's supposed to. He's nuts and took it apart to adjust it, and it seemed like the guts of the switch were loosey-goosey instead of providing some friction-resistance.

Oh the injectors have been dealt with and 2 have been replaced so the problem must be elsewhere.
I've never had a car "fade" the RPMs before, it's a weird experience.

TSI is in the head, TSII is in the intake plenum. TSI is probably more important, input air temp can't be as important, except in extreme climes.

Thanks I really appreciate your input. Hey I thought you were an L-jet guy! Oh man so much to learn...

Edit: found this on Samba:

(2) A great many of the later production of the TVS's....had abnormal slop or space between the two main pins that are the on/off stops for the floating forked switch.

[Bleyseng]

Ok, on a type 3 the TS1 is the CHT sensor...thats the one that matters. The TS2 if unplugged will richen the mix slightly overall.
Actually, I am more of a djet guy working on 914s since 1995.
Here is the bible on Djet-http://members.rennlist.com/pbanders/ if you want some reading material.

[hambone]

Apparently the issue was caused by a faulty throttle valve positioner. I will report back if the issue reoccurs. Onward!

[Bleyseng]

Glad to see it worked out for you....

[Amskeptic]

Apparently the issue was caused by a faulty throttle valve positioner. I will report back if the issue reoccurs. Onward!

???

Throttle Valve Switch?
Colin

[hambone]

I've seen it described both ways. Seems that TVP is more commonly used for that carb dashpot contraption though.
Throttle Valve Switch it is.