Howdy,

I have a 1975 2.0 that I recently acquired. It did the 3 hour drive home; no problem. I’ve put probably 100+ miles on it since with no problems other than a high idle. (~1800 rpm which I know is high but it still ran smoothly)

Issue #1
Until I took it out the other morning. I parked it and went to the spring game during which time the temperature climbed to 90+ degrees. On the way home after about 5 blocks while sitting at a light; the rpms suddenly just dropped. I kept it going but it would just bog down and attempt to stall. Then it would surge back to normal and go half a block and then just drop out again; no power and trying to stall. So I parked it and grabbed a ride home. Since the only thing out of the norm was that this was the first 90+ day I’ve had it. I decided to go back and give it a try at dusk once the temperature had dropped. Sure enough it fired right up and I drove it home with no issues.

Issue #2
After some researching, I figured between Issue 1 and the high idle I would poke around looking for vacuum leaks, checking for a stuck open AAR, etc. I popped the air filter housing off to get a better view and was surprised when I could find the AAR. Turns out there is no AAR or Decel valve. The CSV is unplugged as well. Obviously, it has run without them but I’m not sure that is the best long-term option. I also don’t know if this would contribute to/exacerbate Issue #1.
(side note: not sure about the how the hoses are run. For example the hose running from the throttle body (retard?) to the oil filler and not the distributor? And is that a 1.8L oil filler?)

I haven’t experienced Issue #1 again but it also hasn’t been hot out if that had anything to do with it.

Last observation: I put the air filter housing back on; tightened it up on the throttle body then put the hoses back on. Idle at start-up dropped to ~900. After warming up for 5-10 minutes it climbs up to ~1200 and settles. So maybe there was a bit of vacuum leak in one of those connections and still a bit more elsewhere that I can look for. However, it run worse than before. Any time rpms are below 3000 it runs very choppy, especially when accelerating.

So any ideas on my best move forward? Are they separate issues or maybe intertwined? Address one before the other independently? Which one first?
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Sounds like it's overheating among other issues.

Wondering if you have clogged cooling fins, CHT is getting very warm = very lean causing the running issue on a hot day.

Vacuum leaks causes all sorts of issues. Check and replace hoses, ensure they are connected correctly etc.

If you have one of those cameras you can snake under the tin, take a look. Also check your cooling intake down at the front of the engine/crank. Make sure there isn't something like a rag stuck in there.

Looks like there's a mix of things going on here that could use a little cleaning up. With the AAR and Decel valve gone it can be a little hard to just go off a known diagram.

The head vent and PCV system are from a '73-'74 model 2.0 setup. Oil filler is not a 1.8L part.

The PCV should have the branch fitting removed and have a hose going to one of the two ports on the bottom of center manifold that are capped(the ones pointing at the distributor). If they are different sizes pick the one that fits the hose the best and leave the other capped.

The port that has the head vents coming to it(mounted near the dip stick) should have a hose going up to the top of the air filter housing above the throttle body.

The short vacuum hose going from the TB to the branch fitting currently on the PCV should be removed and the port on the TB capped. Save the branch fitting if it's not in terrible shape if you plan on sourcing a decel valve in the future.

Can't tell in the photos, but the plastic portion of the CSV has the fitting in it(kind of looks like a plastic spacer) for the AAR to be routed to. If that fitting isn't capped you have a pretty sizeable vacuum leak.

The air cleaner port that has the orange cap on it would have been for an Evap hose. It's fine for now. The other two unused ports on the air cleaner above the TB can be capped as they were for the Decel valve and the AAR.

Hopefully that will at least get your FI in a healthier state hose-wise. If you're still chasing your hot issue or anything else comes up that you want to check/troubleshoot this site is full of info: Djet Info

Thanks guys. I need to check my eyes I totally thought that branch was a nipple coming off the oil filler when I was looking at it.... doh. I'll check those items as well as re-route those hoses as specified.

-J