RESOLVED: 3 weeks troubleshooting, still stuck

[Valaas]

OK good so MAP sensor may be ruled out.
You could try put the vacuum gauge (on a short piece of hose!), connected to each of the 2nd set of nipples on the throttle body, in place of each blank, one at a time.
The idea is to see if there is a vacuum leak on any of the 3 cylinders' throttles.

I doubt all 3 transition pieces have the same leak.

I'll do the vacuum test on each blinded line just to confirm leaks on #2 and 3, but I have ordered everything elastomer oe that see vacuum including the blind caps. Willing to go to extreme steps if nexessary to reduce the risk of a vacuum leak chase again.
You know, all this started with a turbo upgrade project. I have had all necessary hardware in my garage for 3 weeks ready, to start fitting, but wanted to spend a couple of days getting the engine basics tip top. Man, did that plan fail miserably.
"Forced air project stopped by vacuum" :-/

 

[TURBO200R4]

I do not know this for a fact so don't carve this in stone. I think that it might run with all the hoses pulled off.
So that would leave the base rubbers or the valves.
Do a compression test to check all three cylinders for valves not seating or bent valve.
The other taught was to beg borrow make or steal a smoke machine and use the tune ecu on tps adjust to close the throttle then pump some smoke in one of the hoses.
A buddy that smokes might be a good substitute lol
Hth

 

[Valaas]

I do not know this for a fact so don't carve this in stone. I think that it might run with all the hoses pulled off.
So that would leave the base rubbers or the valves.
Do a compression test to check all three cylinders for valves not seating or bent valve.
The other taught was to beg borrow make or steal a smoke machine and use the tune ecu on tps adjust to close the throttle then pump some smoke in one of the hoses.
A buddy that smokes might be a good substitute lol
Hth

Did the compression test, measured valve clearance all good. I'll buy the 200€ rubber just to eliminate as many unknown as possible. Been on and off with those hoses, throttle bodies, clips and fuel rail connectors so many times the last couple of weeks it lasts a lifetime

If I need smoke I'll light up a cigar myself

 

[Gerald]

I'll do the vacuum test on each blinded line just to confirm leaks on #2 and 3, but I have ordered everything elastomer oe that see vacuum including the blind caps. Willing to go to extreme steps if nexessary to reduce the risk of a vacuum leak chase again.
You know, all this started with a turbo upgrade project. I have had all necessary hardware in my garage for 3 weeks ready, to start fitting, but wanted to spend a couple of days getting the engine basics tip top. Man, did that plan fail miserably.
"Forced air project stopped by vacuum" :-/

The plan was solid, imagine try to sort out turbo with existing issues.

 

[Neville Lush]

Have you plugged the map sensor into the wrong plug? There's a spare plug in the loom near where map plugs in.

 

[Valaas]

Have you plugged the map sensor into the wrong plug? There's a spare plug in the loom near where map plugs in.

Very good tip. I believed there were only unique male-female plugs but you are right: there are two possible matches for the MAP sensor plug. But I have followed the wiring diagram and measured continuity from the MAP sensor plug to the ECU plug to eliminate bad wiring. So I'm 100% sure.

 

[Rocket Scientist]

I hate to be "that guy", but is it possible the plug wires got mixed up when the valve cover was off ?

 

[Valaas]

I hate to be "that guy", but is it possible the plug wires got mixed up when the valve cover was off ?

You know, I have been hoping for "that guy" to present a simple solution so I honestly welcome any constuctive suggestions.
I have overthinked more than once, believe me!
In the last weeks ordeal I have improved several (although proven unrelated) things, including the entire ignition coils/terminals/cables setup. For the first time in my ownership I am 100% confident that the ignition, from ECU plug to sparks is solid. Including order.

 

[Valaas]

OK good so MAP sensor may be ruled out.
You could try put the vacuum gauge (on a short piece of hose!), connected to each of the 2nd set of nipples on the throttle body, in place of each blank, one at a time.
The idea is to see if there is a vacuum leak on any of the 3 cylinders' throttles.

I doubt all 3 transition pieces have the same leak.

I checked vacuum on each throttle body: All seem good, including the "suspects" #2 & 3! Needle oscillated wildly (as per your warning) but clearly shows good vacuum.
When measuring directly (not teed in) on the tubing feeding the MAP sensor, I'm down to practically atmospheric again.
Disconnected all hoses from the 3 into one fitting and measured vacuum on each body via its vacuum hose, good vacuum on all 3..
Pressurized the 3 into 1 fitting, no leak.
What witchcraft is at play here?

 

[R-III-R Turbo]

I checked vacuum on each throttle body: All seem good, including the "suspects" #2 & 3! Needle oscillated wildly (as per your warning) but clearly shows good vacuum.
When measuring directly (not teed in) on the tubing feeding the MAP sensor, I'm down to practically atmospheric again.
Disconnected all hoses from the 3 into one fitting and measured vacuum on each body via its vacuum hose, good vacuum on all 3..
Pressurized the 3 into 1 fitting, no leak.
What witchcraft is at play here?

Good man you've narrowed down the location of the problem to between the MAP sensor and the 3-1 vac tube merger (inclusive).
Seems like there must be a crack or poor seal somewhere there.

Can you try a different 3-1 merger, and different merger-to-MAP sensor tube?

Tubes need to be the same length and internal diameter as stock, this is important.
A merger could be made with an X or cross connector for vacuum tubing (this is what I use, see below).