Suddenly runs rough, no tach

[Onen]

UPDATE: A couple of days ago I put in new Ignition Coils. That didn't fix my issue. Today I received my new NKG Spark Plug Wires. I put those on, and it started up fine, idled fine, tachometer worked, and it test drove great! Even felt like a little more horsepower.

Interestingly, for one moment, after driving around (rather hard), the tachometer went to 0 between shifts, but then went back to indicating properly. That was the only 'Huh?' moment.

I will put on new condensers, points, and ignition rotor for the distributor this week as well.

Thanks for all the ideas and insights!

[KiwiDave]

Also check out the signal to your tachometer.

I've checked the wiring diagram for your S1.

Look for a yellow/green wire on the NEGATIVE terminal of the LEADING coil. That's your tacho signal. Could be something as simple as cleaning the connector on that yellow/green wire.

This contradicts my previous post on the same subject. S2 and S3 take the tacho signal from the trailing coil.

[Onen]

Thanks!! Great info, I will look at that this week when I do the condensers, points, and Ignition rotor. Appreciate the help very much!

[Onen]

It's been a week or so, and I've updated and changed everything in my 1979 RX7 that I said I would: the plugs were new NGKs, I put in new Ignition Coils, New NGK Spark Plug Wires. In the distributor I put in New Points and gapped per Haynes manual, new Condensers, New Ignition Rotor. I'm STILL having a problem!!

It has a rather difficult start. It didn't used to.
It idled fine with the choke out on start up, then idled at 2k rpm with the choke for a couple of minutes. It doesn't stall, but it runs so rough, especially above 3800rpm. I'm noticing at just over 4K - 5k it's very rough, no power, just rough and not moving.

I went back and checked the Points gap, then the spark plug wires. Seems good there. I'm deflated by this because it was running so well for a while, then it slowly just started to dog out.

Thanks again for any thoughts.

[DKWW2000]

If not already done so change the Fuel Filter underneath by Diff, & whilst there check the pump is operating properly (no dodgy connections) fuel lines not collapsing etc. Perhaps some carb cleaner (spray type) would be worth a try?

[gt_james]

Sounds exactly like mine with a faulty igniter, are you sure the S1 has no igniters? Not familiar with the older points dizzy myself.

[danny]

I think there is a vacuum problem or the gasket between inlet and engine block is leaking. When I thoroughly cleaned up the engine of my car, the seal turned out to be completely rotten.

[Onen]

Thanks for the ideas!
There aren't any ignitors. I double checked, those seem to have started in 1980.
I did check the fuel filter. It is new as well, maybe 100-200 miles with it so far. It looks clean. I will take a look at the fuel pump. I guess I would listen to it? What's interesting is that it doesn't stall and it's a bit rough from idle to 3K rpm or so, but really rough after 4K, with no power.

The vacuum leak is what I was thinking. I've looked already, but will take an even closer look. Danny, what seal are you referring to? And you noticed it just by cleaning the engine in the car?

Much appreciate everyone!!

[DKWW2000]

Sounds exactly like mine with a faulty igniter, are you sure the S1 has no igniters? Not familiar with the older points dizzy myself.

I think the older "Points" systems used condensers that can fail causing such issues

[Onen]

I did just replace the condensers. Perhaps I need to replace those again?