Hi guys,

need some advice on a friend’s 1984 928S here locally.

car was undergoing some cosmetic restoration and came back needing mechanical work. Some of the symptoms are as follows:

1- steering has a serious problem where I can rotate it to 70 degrees and the tires barely move. A massive dead spot in the center and the car drifts around.
2- Oil pressures gauge is pegged to 5 bars at idle even after warming up. It does not budge. (by comparison mine shows 2-3 depending on ambient temp… even lower during the summer)
3- idles at about 1000 rpm but the engine is running smoothly without audible sounds indicating an major mechanical issue.
4- when I press the accelerator (even flooring it) the engine does not pickup pace at all at the beginning. Like totally out of sync between the throttle linkage and injection state. It eventually moves but lethargic at best.
5- car would die intermittently as we roll to a stop or brake
6- tail lap fail is on but the bulbs are working
those are just starters.

any thoughts or assistance is appreciated as I am more familiar with the LH and this being an L I have very little experience. We have it scheduled to go to the tech that has been looking at mine but wanted to get pointers from here as the knowledge on RL is extensive.

 

To fix your idle issue...

Check for vacuum leaks. You can use the water mist technique (safest), a smoke generator (also safe), an unlit propane torch (not so safe) or spray brake cleaner (unsafe) to test for vacuum leaks. Check the injector seals, intake runners, butterfly valve throttle and air-fuel meter o-ring. The vacuum lines could have also become disconnected. Check the lines to the brake booster.

Check that the aux air valve under the air intake is connected, leak free and plugged in.

I have this exact car,. The L-Jet system is sensitive to false air.

 

Yes the vacuum leak was the first think that crossed my mind since my friend seems to have issues with his AC functions to start. Leaking/torn diaphragms are a well known problem with time and his dash was out for recovering so no idea if they knocked something there as well. I told him the first thing is to inspect the entire vacuum system to ensure integrity using a smoke machine.

 

The hard black nylon vacuum line that leads into the cabin comes off the brake booster vacuum line. There is a blue one-way valve connected at the junction. You need a vacuum pump and gauge (Mitivac) to test the vacuum of everything in the cabin. Pop it off and start pumping. It take a bit of work but it is a simple check (5 minutes max). You can also disconnect and plug this line temporarily if there is a bad leak.

If there is a leak check the black vacuum line at the firewall and ensure it isn't cracked. Follow it inside the cabin and down to the electronic valves under the center of the dash. You can open that up from the driver's side carpet panel for inspection. If you remove the radio & HVAC, you can make enough room to remove the valves and check them individually with the gauge.

If the dash was removed, it is possible that they damaged the vacuum lines & forgot to reconnect them. The rubber vacuum connectors also become hard plastic over time and easily tear/break. It is also possible that they cut or pinched or disconnected the various electrical harnesses. If you have a cheap borescope that can be used to find disconnected lines and wires.

 

My '84 US auto oil pressure gauge is always at 5 bars. This is normal.

 

If warm the oil pressure gauge on a S should drop to 2,5 -3 bar at idle.