1988 3.2 crappy idle and shakes
 

1988 3.2 Carrera, first run of the year. Idle is not that great. Car shakes. ICV works and was cleaned twice just in case. New spark plug leads and plugs. Shop suggested valve adjust. Car is going in end of August. Any easy things to check?

https://www.youtube.com/shorts/DXdWNIc9GwY

How long was the storage period? Was there any short 10 minute start ups over winter?
Plenty of temp fluctuations I’ll bet. Moisture affected gasoline could be a culprit.
Gas tank/fuel stabilizer additive used?
How much gas left tank? Drain or syphon and fresh fill up.
I’d try and run the old gas out with an injector cleaner (proper ratio) at a highway speed for at least 50 miles (80k)round trip.

Pour a bottle of Chevron Techron Concentrate in the tank and drive it hard. If it doesn't smooth out, then start thinking about other things.

Re valve adjustment: When was that last done?

Could be a stuck injector. Put a long bladed screwdriver on each injector and listen to see if each is clicking.

Car was parked in my insulated garage. Stabil was used in the gas which was fresh and about 1/2 a tank. Never started during that time. I am going to fill it up and run some injector cleaner and run it hard for a while. I have one of those stethoscopes so will see if I can hear the injectors. clicking. Valves were done a few years ago.

Valve adjustment: Time doesn't matter. How many miles ago was the last adjustment? I would not mess with the valves if it was less than 10,000 or so. Just drive it.

I would not overdose the injector cleaner, it could cause other issues during the cleaning process like too much is not anlways better.
I always dilute at the proper rate per gallon. Stabil 360 is what I use, formulated for storage and cleaning whereas Stabil regular has less if any cleaning properties. I switch over to Lucas cleaners for 3 season driving.
Top off the tank with 93 or 94 octane non-ethanol if you can find it (at a marina). Shell nitro is a good detergent as is Chevron or Sunoco all depends on the market area. I’ll top off every few tanks with a top tier gas when I can find it.

If the new plug leads are Beru they could be the problem...

So, it was at a shop.

What have they checked ?

Further, shop was on holidays so goes in next week. Have been doing fast drives in 3rd gear around 4k rpm for half and hour on the highway, runs a little better. Did the stethoscope and all the injectors are clicking in time with the engine rpm. Quite surprised at how well you can hear the injectors. Car still idles like crap and backing off the throttle causes surging, like 3 times a second. I have to push the clutch in and clear the engine. Also really stinks like unburned gas. Last valve adjust was over 15k kilometres ago.

Maybe first consider changing the fuel filter.

https://forums.pelicanparts.com/porsche-911-technical-forum/1004817-3-2-pulsing-rpm-when-idle.html

Read this as well

A smoke test , firing order and fuel filter is where i would check next..

I went through this 18 months ago and fuel filter and setting the idle stop switch fixed my problem. At the same time I replaced the fuel pressure regulator and damper and idles perfect now.

MAF sensor issue?

Look for vacuum leaks. Tighten down the head runner bolts. Really. They come loose over time in a 3.2.

A vacuum leak can make a 3.2 idle like crap. As soon as my bad head runner gasket was replaced, idle went back to perfect.

Just got the car back, runs a lot better. Throttle body was removed because of silicon was found on sealing surface, cleaned silicon off and new o ring. Smoke test, no leaks. New ignition harness (BEHR) old one had over 100k on it. New plugs. Cap and rotor good but cleaned. New 02 sensor, over 100k on it. New fuel filter. Found vacuum line to fuel pressure regulator was disconnected (!), connected back up.
Engine sounds way smoother and engine doesn't shake. Idle is still a little up and down and slow to respond. Found that the ICV was “sluggish”. I ordered new from MAF Service. They changed the idle mixture, doesn’t reek of gas now. Checked valves, all good. Raining like crazy. Why didn’t Porsche use fender liners? When rain stops will do proper test run. Suggested that over winter, I should pull injectors and get them cleaned. Thats about it.

Some of what you are describing sounds like a vacuum leak.

Sounds like that disconnected vacuum line might have been responsible for a lot