My 2.0 D-Jet motor runs hot,, Edit - idle fixed, vacuum leak found Options

[Cevan]

I swapped out my 1.8 L-jet motor for a stock 2.0 D-Jet motor. I’ve put about 75 miles on the car since the engine swap. According to my CHT gauge, it seems to be running hot. I had a similar problem with the old motor. That engine was running lean and I adjusted the AFM and got it to run around 325-350 on the highway (70-75 mph).

The 2.0 motor runs around 350 in 3rd or 4th gear at 3000 rpms and goes up from there when it’s on the highway. The gauge is definitely reading hotter temps across the board compared to the 1.8 motor.

The only issues I have currently are a minor vacuum leak (idle is a bit high) and a TPS that is a bit worn. The car runs great otherwise. It accelerates nicely (noticeable improvement over the 1.8).

All the tin is in place, fan is intact, no blades missing. Dwell and timing are correct. Valves adjusted. Injectors cleaned and tested. MPS good and is the correct one for a ’74 2.0 motor. New points, cap, rotor, plugs, plug wires, vacuum lines.

I need to pull a plug and see if I see signs of it running lean. This is what I suspect. I will also check the fuel pressure. Could this be a timing issue? Could it run cooler at a different timing setting than the factory spec? Any thoughts? (IMG:style_emoticons/default/confused24.gif)

I also can't get the idle below 1300 rpms. I have the idle adjustment screw all the way in and when I go to turn the idle mixture screw on the ECU CCW to get it below 1300-1400 rpms, it does this up and down thing with the revs. I've sprayed of starter fluid at every place a vacuum leak might exist and the revs don't change. I'm this close to putting L-Jet on the damn thing.

[Cevan]

Vacuum leak found: PCV valve. I pulled the vacuum line and plugged it and then messed around with the idle screw and the ECU adjustment. I now have a nice idle at 800 rpms. If I hook it back up, the idle goes back up.

As I recall, my PCV valve doesn't have any spring or disk inside it. That explains alot. It's basically just a port.

So my next question is can I convert mine to the '75-'76 setup that eliminated the PCV valve? If so, do I just connect the vacuum hose from the PCV valve (now really just a port) to the airbox?

From PBanders site:

The D-Jetronic PCV valve has two flow rates: metered (when the disk is on the intake manifold side seat) or closed (disk on crankcase side seat). This design is not optimal:

The metering slots restrict the flow of blow-by gasses under full-load conditions, causing the excess blow-by to flow back through the crankcase ventilation system.

The flow/no-flow nature of the PCV valve requires that the metering slots be somewhat larger than needed for idle conditions, so that there is sufficient flow under most operating conditions. This increased flow at idle causes the intake manifold pressure to increase, leading to a richer idle mixture and increased emissions and lower fuel economy, as well as potential idle stability issues.

These limitations are likely in part what led Porsche to revert to a passive crankcase ventilation system on the 75-76' 2.0L models, where the PCV valve is eliminated, and the breather on the oil filler is connected to the air box instead of the intake manifold.