L-jetronic Troubleshooting, Runs Rough and Runs Rich Options

[BENBRO02]

It starts okay when cold and only has a slight miss but as it warms up it starts to miss more frequently, bucks, and if hot and idling may cut off completely. If I'm on the highway it may lose 20 mph before it starts running well enough to maintain speed or accelerate. I have recently had the following replaced:

fuel tank
fuel pump
fuel lines and hoses
fuel sending unit
vacuum hoses
large and small injector seals

The shop also checked the vacuum advance and cleaned the injectors.

I emptied my bank account with the repairs so now it's time for me to find the problem. Any Ideas? The car has a Pertronics ignition.

[djway]

First since you are challenged, as we all were and are to some extent, find every L jet manual out there, download, print and read. Over and Over and Over. I had never worked on FI before and I discovered bad wires, multi vacuum leaks, a bad potentiomoter board, weak CHT sender, air density sensor was corroded and the flap spring had been moved I assume to adjust for all the air leaks. It started as the motor cutting out every so often and belching smoke. Each time I found a problem and fixed it the car ran worse until I found all the problems.
I think I started with checking continuity on all FI related wires. Then I went to vacuum leaks and found a torn plenum and a torn tube end. I did a leak test of the injectors. Checked the AFM board to adjust the wiper but it had cracks so I replaced that. Checked the cold start valve for proper operation. Checked and cleaned the full throttle position mechanism. I then checked the resistance of the CHT and it was not in spec and they were hard to find before 914 Rubber started selling them. I then checked the AFM air density sensor and found the resistance was way off so I opened it up and cleaned the contact and bingo. After that I took an AF Meter and made an exhaust extension to hold the O2 bung and jumped on the freeway to find the proper stoichiometery for the mixture. Kept pulling off the freeway and moving the spring until I got it right at 3000 rpm. She now runs like a champ after barely limping home the day of purchase.
I knew NOTHING when I started. The L Jet service manuals have a check list of what to do. Start at the beginning and methodically work your way through one step at a time. Don't skip steps. If you are satisfied after completing each individual step the last thing would be the brain and I did not look into testing that.
You can do it. Read, learn, go slowly, methodically and you can get there.