Cold Start Issue 914-4, Admitting I'm stuck and asking for help Options

[Blue Lightning]

Car: 1976 2.0, FI

Background: bought in November last year. I am least the 4th owner. Drove a couple times, then plugged up the fuel filter (? no fuel pressure when the fuel pump was running, but see note below on replacing the fuel pressure regulator), so spent a couple months with the gas tank out and replacing the fuel lines, pump (and yes, filter). Read a lot in the meantime, so corrected vacuum line issues (vac advance was connected, replaced all the lines that didn't already look new, added hose clamps). But where the car started and ran well last year, I can't get it to happily start any longer. While cranking, it will skip and catch. After a few minutes of cranking (and skipping and catching) it will finally start and run fine for a few minutes but only idle around 1000 rpm (until the AAR warms up the rest of the way?), then dies. Starter fluid has no effect, so guessing it is running rich? Pulling the air hose off the cold start injector while running causes the idle to increase to maybe 1400 rpm (but with hunting, as you might expect with that big leak). There are a lot of threads on what to look for when the engine is running lean, but few on it running rich.

Some things I have checked:
- AAR works (https://youtu.be/YmO1ZCLDB7g)
- Compression is good (130-140 psi cold)
- Replaced the MPS last weekend with new one from autoatlanta, after finding the previous one would not hold a vacuum
- Replaced fuel pressure regulator after finding it bad (yes, I've been told these never go bad, but this one would not hold any pressure). Fuel pressure set to ~29 psi.
- Timing is good (~27 degrees at 3500 rpm with vac retard disconnected)
- Vac retard mechanism is working (checked with vacuum pump)
- Spark on all 4 cylinders (checked by timing light)
- Smoke tested the intake...only leaks now are the bearings on the throttle plate
- CHT reads 2k at cold, ~250ohms at warm/hot (at splice connector)
- Plugs look okay (see attached)
- Fuel injectors are all spitting fuel (checked into bottles...all about the same) and have new seals
- idle adjust screw has some control, but I cannot get the idle above 1000 rpm with it
- valves adjusted back in December (my first time, but the car runs so I assume I didn't do too bad of a job?)

I'm at a loss of what to try next. (IMG:style_emoticons/default/hissyfit.gif) I'd like to consider myself fairly good with cars (we have a 1966 Mustang, as well as a Mazda RX-8 that I have kept running for >20 years), but I'm about ready to throw in the towel and have the 914 towed to someone smarter than me!

Thoughts?

[Superhawk996]

No immediate answer but let’s work through this

Where is the insane high pitch whistle coming from? Seems to be the air bypass as it changes when you adjust. But also seemed to be reduced when you tried to put the air filter on.

Were those backfires around 6:17 - 6:20? Those don’t seem to start until the engine warms. At the end of the 8 minutes or so - how hot are the heads? Do you have a means to gauge the head temp at the end when it starts running rough? We could also go by CHT resistance at the end.

The extended cranking to start is not right. If you shot a little starting fluid at the very beginning when it’s extended cranking and dead cold, does that help or hurt?

That it actually runs and revs is more than I got out of reading the initial posts. The video is helpful.

You mention that the MPS is new / rebuilt from AA?:
1) is the part number correct and matching the ECU and the rest of the system? Ie - not all MPS are the same.
2) have you vacuum checked the new one? For some reason I’m assuming yes but not sure.
3) what vacuum level are you pulling on the plenum? I’m wondering if that whistle is a huge vacuum leak somewhere that is killing the plenum vacuum

[Blue Lightning]

Where is the insane high pitch whistle coming from? Seems to be the air bypass as it changes when you adjust. But also seemed to be reduced when you tried to put the air filter on.

3) what vacuum level are you pulling on the plenum? I’m wondering if that whistle is a huge vacuum leak somewhere that is killing the plenum vacuum

Move video around the throttle body: https://youtu.be/lWhufzgEm3M

as mentioned in my reply to emerygt350,the plenum vacuum is pretty low, so that would seem to be the problem...