DJet Frustration, Ever play that Whack-A-Mole game at the arcade? Options

[ConeDodger]

Remember that arcade game Whack-A-Mole? You take a hammer and whomp the moles as they come up through the random holes? McMark and jcd914 and me had that kind of day playing Whack-A-Mole with the DJet on Jim's engine (jcd914) in my car...

Recently the engine started running bad. It had a low speed miss and then would go like stink when you got into the advance curve. I have a bunch of new 914 DJet components so I started throwing parts at it. This is a method used by people who aren't mechanics to fix something they don't want to pay a mechanic to figure out and fix. Take a note if you aren't a mechanic - this method is often more expensive then just paying the damned mechanic. So, I replaced the MPS with one that I bought from George at AA a few years back and never really used, I replaced the harness with a Bowlsby harness, I put a resistor in the CHT circuit... Each thing I did made it run better in some ways but often worse in others.
So, I decided that since I was having the Sacramento Porsche Family Reunion today and McMark was coming up, how about having him take a look at it and paying him for his time. Mark was game. He brought his LM 1 Wideband AFR and we methodically went through the tuning process. Here is where the Whack-A-Mole game began. Everything we did would improve it but unmask some other issue. Some things did nothing when they logically should have. We replaced the distributor with a rebuilt one from Rich Bontempi, it ran worse. We discovered that two injectors were not firing. So the distributor was good but the trigger points, which were new by the way, were bad. Swapped in the trigger points from the original distributor and it ran on all cylinders again but still ran bad. Lean, very lean... Then Jim Dupree pulls in the driveway and steps out of his car with an MPS that he pulled off of one of his spares. 30 seconds to plug in the vacuum line and the harness plug and the problem is solved. Turns out the new MPS from AA is bad or badly tuned for the motor. I suspect the later as it will hold vacuum.
So after three hours of Mark's time and lots of parts. The engine - Jim's engine runs very nicely again... Ahhh... the joys of a 30+ year old car (IMG:style_emoticons/default/headbang.gif)

[agentblr]

Maybe a stupid suggestion but have you tried a different fuel pump?? I had a similar deli ma with my 2.0, started throwing parts at it checked and re-checked everything a dozen times, fuel pressure always showed 29 psi. Car would run rich then lean out and backfire.I finally just gave up and tried to drive it, then one day it just died, would not restart. The pump kicked it. New pump solved all my problems and has run like a champ since. I though fuel pumps either worked or did not....mine died a slow death.

[pbanders]

Maybe a stupid suggestion but have you tried a different fuel pump?? I had a similar deli ma with my 2.0, started throwing parts at it checked and re-checked everything a dozen times, fuel pressure always showed 29 psi. Car would run rich then lean out and backfire.I finally just gave up and tried to drive it, then one day it just died, would not restart. The pump kicked it. New pump solved all my problems and has run like a champ since. I though fuel pumps either worked or did not....mine died a slow death.

Your experience points out the issues with diagnosing problems on these 40-year-old cars. At this age, just about every system is suspect and has to systematically be checked out. If you'd done a fuel supply test (measures how much fuel the pump can deliver in 1 minute), a test you do BEFORE checking out the FI system, you'd have caught this before throwing expensive FI parts at the car. I've got some checklists on my site on how to go through the car systematically to catch such problems.

Issues like this are why I'm always reluctant to diagnose a specfic problem over the internet, without having seen the car or seeing all the checkout data that was done before going after the FI.

[ConeDodger]

Maybe a stupid suggestion but have you tried a different fuel pump?? I had a similar deli ma with my 2.0, started throwing parts at it checked and re-checked everything a dozen times, fuel pressure always showed 29 psi. Car would run rich then lean out and backfire.I finally just gave up and tried to drive it, then one day it just died, would not restart. The pump kicked it. New pump solved all my problems and has run like a champ since. I though fuel pumps either worked or did not....mine died a slow death.

Issues like this are why I'm always reluctant to diagnose a specfic problem over the internet, without having seen the car or seeing all the checkout data that was done before going after the FI.

Which is exactly why I think you ought to jump on a Southwest Airlines flight. You could be here in 3 hours... (IMG:style_emoticons/default/lol-2.gif)

FP is a constant 34psi... Have not checked delivered fuel in 1 minute though... I have the fuel line guaged with a pressure guage.