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Hello Again All,

I had been busy with work, so the car went on the back burner for a while...

I am back on it at the moment and have it running and driving. I just passed its first roadworthy inspection in 17 years!!!!

I have done about 4 hours run time since the first run and oil change. it runs OK, however trying to run and hold low RPM whilst driving (below 2krpm) it gets very jerky, or starts to buck. I have to accelerate to stop the bucking. When i accelerate it pulls hard!!!!

Cams were reground by someone here in France, they are a little bigger than 964 cams (bit more lift and duration) with lobe separation of 108 degree. it idles lumpy, but never stalls. (see the vid above)

I have set the timing at 7degrees as it seemed better and less jerky at 7 degrees, i may try more soon, i just recieved a Classic Retro fit CDI+, so then i can adjust the total too.

% of Co2 is 3.5. I know that may be high, but she is still new...

Does anyone have any experience with bucking and what the cause of it can be????

Thanks
Christian

Sounds to me that there are still some things to fix. Probably as mentioned vacuum leaks and misadjustment of the CIS. Ignition is worth a look, but from my side I would check up the CIS system. I had similar problems with high idle - it was a totally misadjusted CIS. While playing with the CO screw, idle screw can mimc a proper starting and idling engine when cold, but it shows exactly such problems with too high idle and stalling when being warmed up.

Follow the steps in this video for the basic setup of a CIS engine (the entire video is worth a look):
https://www.youtube.com/watch?v=K-OvjlkrgNo&t=2529s
I spooled it to the sensor plate height adjustment, this has a huge effect on how the engine starts and run.

First and foremost follow these steps for a proper adjustment of a CIS engine:
1. Sensor plate height
2. CO2 screw (the video shows Curts preferred way of dismantling one line on the FD, I prefer the Bosch way on hearing the injectors squeezing)
3. Idle screw (close completely on sitting engine and then 2 turns out)

It the FP and CP are good the engine must start rightaway and idling with 5-10° ignition advance. As well cold and warm! A different camshaft affects the idle of course, it will run a bit more rough on idle, but it must start and idle as well as a stock engine beiing cold and warm. Probably you have to play around with CO and run a tin ybit richer than stock, but never as much as 3% CO or more I would say. I own a 930/16 with WebCam 20/21 grind camshafts and it starts rightaway and idles with approx. 1% CO and running stock lambda ECU.

Afterwards fine tune the CIS as follows in this video: https://www.youtube.com/watch?v=Ii5k773lwKs

Curt has collected some more information here: https://www.klassikats.com/document-center/

Thomas

Try it and see what happens.......

Quote:

Originally Posted by ahh911 (Post 11792601)

Tony,
I did think of the screw binding if turning to the max/ or min as a negative and wonder if two turns back was enough to shut off the fuel flow with plate at rest, I assume some success was had or it wouldn't have been mentioned, but you seem in total disagreement and have seen plenty of these on your workbench so there may be variability and unknowns.

When I did this, the engine was removed for overhaul, took a 1/2 thereabouts inch plywood, drilled some injector holes into it and put the cis without shroud but with input air arms ziptied to plywood, attached some dollar store barbecue bottles with scale under injectors and slid the thing into the engine bay with something underneath to hold it up, some big storage container, then plugging in the fuel lines and measuring flow at different plate levels looking for uniformity with the plate slightly lifted then at a much more aggressive lift of the plate to simulate full throttle, thereabouts. Also checked drips with plate at rest position. Again, all while the engine was out for work over winter.

Tony, how do you go about it once it's in the car and you have no confidence that the setting is even remotely close?

Phil

Second pic I believe was testing the thermo time switch in preparation for the test with fuel delivery. Used a boroscope to look at the wonderful spray pattern coming out of csv, and timed it. no leaks.
p.s. did this with original injectors, then new injectors. I figured I'd purge the old crud out with the old injectors and see if the turn on threshold for new vs old injectors was the same, really saw little difference, but that's the way it goes, did not observe spray pattern as the injectors were new.

http://forums.pelicanparts.com/uploa...1662671395.JPG
http://forums.pelicanparts.com/uploa...1662671395.JPG
http://forums.pelicanparts.com/uploa...1662671395.JPG
http://forums.pelicanparts.com/uploa...1662671395.JPG

Phil,

I missed your post. So let me explain to you what would happen if you turned the mixture screw all the way in (clockwise) as previously suggested:

If you turned the mixture screw CW all the way you IN, you have set it to maximum enrichment setting.
Turning it back 2 turns CCW is not enough to prevent raw fuel from going through the fuel injectors. We are not talking about running the motor, just the FP.
Once the FP starts to run, the six (6) fuel injectors will prematurely send fuel.
Why? Turning the mixture screw CW all the way IN would raise the plunger up and allows fuel to flow out through the 6 fuel injectors. This is some what similar to raising up the sensor plate of the flow meter unit.

http://forums.pelicanparts.com/uploa...1671213256.jpg

You surely know by now what happens when you lift up the sensor plate while the FP is running. With the mixture screw turned in all the way minus 2 turns back, the plunger is already raised up and will prematurely deliver fuel once the FP starts to run. Try it and keep us posted.

Tony