(SOLVED 4/15/21) A Call for Help - 1990 Saab 900S Idle Surge Problem

Описание: **As of 4/15/21, the problem has been solved. I've posted a new video of my findings. It was the mass air flow sensor.**
   • Solved! 1990 Saab 900S Idle Issues Fixed (...  


A short video today. I'm mostly waiting on parts for the van build so I gave the Saab some attention. It's been sitting for a few weeks because it will not drive right.

Everything I've attempted for fixing the lean condition and idle surge on my 1990 Saab 900S:

-Isolated vacuum line from everything except the vacuum canister and fuel pressure regulator
-Replaced all vacuum lines with silicone hose
-Replaced intake gasket (see video)
-Replaced Idle Air Controller (see video)
-Cleaned (several times) and tested (according the Bentley manual) the Mass Air Flow Sensor
-Verified fuel pressure with gauge on fuel rail (40psi at idle)
-Replaced all rubber grommets on intake manifold
-Replaced fuel injectors with used lower miles version (from a Volvo)
-Put new O Ring on Throttle Position Sensor (might need a new one)
-Used a DIY smoke machine on intake. No leaks found (not 100% confident with that result)
-Replaced O2 sensor with Bosch part

I'm fairly certain the high idle is because of an air leak. A vacuum gauge came up with a similar conclusion. I am suspicious of the ECU but I don't want to go that way unless I absolutely have to.

Other then the O-ring on the TPS, I am officially stumped on why my car won't idle at a normal RPM. If anyone out there watching has dealt with this problem, please let me know what you did to fix it.