Why does my '74 1.8 sometimes run so RICH?, After a bit of driving, it won't idle Options

[drdstny]

Hello many kindred,

So I drive my 914 every day, about 60 miles per day to be exact. Almost immediately, I noticed that (this is so hard to believe I'm having trouble posting) if the left engine heater hose comes off the heater blower, the car won't idle and will stall unless I keep the R's up above 2K.

So...I fixed that with some Tape.

Before I Taped it to the blower, it was predictable: if the car suddenly started running rough, rich, with smoke pouring out of it, then I knew I needed to put the hose back on.

Since I "repaired" the hose, now it's less certain. About halfway to work, once I hit traffic and have to stop-n-go, it idles rough. VERY rough, and I need to side-step the gas to keep the engine from stalling. Smoke will come pouring out of the tailpipe, my eyes water, can't breathe, lose faith in humanity, diet goes awry, idle won't calm down...you get the idea.

Seems like it only does this after about half an hour of driving, and USUALLY letting it sit for a couple hours will make the problem go away. Not always, but usually.

The first thing I tried was changing both seals (O-ring and gasket) on the oil cap (recall it's a 1.8), but that made zero difference.

So...anybody have any idea what's wrong? Just as good: anybody have a list of things I can test or replace until the problem is fixed?

This is a serious issue, and the last two tanks of gas have been sub-20MPG so I'd really appreciate the help. I'll send something nice to the person who gets me out of this jamb.

Thanks!

[drdstny]

OK, found that problem and created a new one.

On top of the engine, there's what looks like a secondary air valve of some kind. It has a big end with an electrical connector and a smaller end for a hose & elbow to slip on.

Looks like someone tried to pry ON the rubber elbow, because the metal part is cracked all the way around the bottom where it joins with the main body but outside the protection of the rubber elbow.

I guess what was happening is that once the engine warmed up fully, that crack would widen and Something Bad would happen. I snaked one from a junkyard 914, popped it on, and the problem went away.

However, now I have a different problem. Right about 3200RPM, the engine seems like it's out of gas, it just stutters really bad like it's starving (not lean, starving). The engine works fine, doesn't smoke or anything anymore, but this is a very drastic way to recover MPG, dontcha think?

Before I go buy a new secondary valve (thinking the one I got was no good either), I want to make sure I should. Apart from the richness issue, I never had problems going to 5,000 before, so I'm almost positive it's this thing.

Confirmation?

Thanks to ALL who replied, because that got me thinking and looking at simple stuff like I should have to begin with.