idle adjustments on the 3.5
 

I am struggling since a while with the idle of my d-jet 3.5.
At start up I experience around 1100 rmp and with this high idle the gears bang when shifting from P into R and 4.
At hot idle the engine is at lowest possible which is defined by around 550 rpm including AC and gear in R or 4.

So my thought is to test idle speed and qualities (cold/warm/hot)if I take off the vacuum retard entirely and close the holes. What would this do?
I have already arranged, cut and capped the vacuum pot. This means that at idle timing is at around 10 degrees BTDC (versus 2/4 degrees ATDC) and adjusted idle screw at 700 rpm w/o gear and AC = around 550 w/ AC and gear.
So I'll test what the result will be when I start up the car in the morning.
My hope is that idle is lower in the morning relative to the 1100 rpmwith the retard vacuum.

I heard that euro versions don't have the same vacuum pot for retard or don't have it at all. Who can help?

Martin,
If everything is working and you start up with a/C turned on, then the retard is disabled anyway. Where you are, I would think that would always be the case? That would be a way to check the difference between idle rpm with and without retard. With A/C off, retard should kick in and engine speed should be lower. So maybe start with A/C off?

These cars all run at high rpm when first started. 1100rpm is normal and better than most!. It's true that transmission clunks when I first reverse out of garage and again when I go into D for first time. But engine quickly warms up and idle rpm in gear drops to 550 range.

I don't know for sure, but TDM for '72 euro 116 engines shows vacuum retard timing settings.

To slow engine down, perhaps you could reduce idle air flow. The engine is mainly revving high because teh AAV is still open. I read here of one mod where AAV was replaced by a motorized AAV off a Saab. It could be adjusted from cabin. If you just squeeze the rubber elbow at exit of AAV you can see the affect this would have.

Hi Graham,
yeah you are correct with the AAV. Probably I was mistaken with the Euroversion. In fact I was starting the car with engine 'cold' and the vacuum retard disabled this evening and the engine was surging, going up and down in speed...however it was not a tick lower...1100. Don't know about the surging. I'll explore tomorrow.
About my AAV: I have tested mine a while ago and it was working relatively well. However you gave me the idea...I could try and reduce the area of the fully opened AAV as a basis....by installing a reduction sleeve for instance. This should reduce the airflow with the cold engine and lower idle?
I am starting typically with A/C off.
Martin

No luck so far with improving idle.
Starting in the morning without the vacuum is causing surging. Bad.
So I am back to original setting.. which at least works somehow but gives a bang.
AAV is just a bit too open for my mornings. So a mechanical reduction would probably do the job but I haven't figured it out yet. I put in a rubber hose reducing the area by roughly 50% for air does Nothing. I'll keep testing.
The Saab adjustable AAV (Graham mentioned this one) might do the trick?
I know finally it would be best to just rebuild the transmission.... probably what I'll do.

the AAV sounds to be the culprit, I am thinking at some point to look seriously at teh SAAB set up or similar. Right now mines open a bit too much and I have high idle but its not a big deal
Mine sometimes surges and this is definietly related to the AAV . It happens when the AAV is open too much and the engine temp is calling for less fuel happens for about 30 seconds and once closed and engine warm , it ceases.
One thing that helped my idle issues a great deal was a complete once over , tune up of the throttle plate . Setting the correct opening and making sure the sweep is working The technique is on here somewhere, I think Graham posed it awhile back.

These things tend to get sticky with age. Try squirting some WD40 in the valve.
Since they also idle quite high at first even when operating properly, I'm considering installing a "reducer" to restrict the air flow even when fully opened. When/if I do it, I'll report results.