1991 Civic: starts, runs until it warms, then chokes and won't start

Maintenance/Repairs
1

Alright. I no longer have any idea what’s going on with this car. So, if you know what might be happening here, I’m all ears:

I’ve got a great little 1991 Civic DX, 1.5L manual. It’s never let me down and I love working on it.

Stalled on the highway a couple weeks ago and I couldn’t get it re-started. Over the years, it’s had a bit of a personality where it chugs and occasionally stalls at a low idle, or when very slowly accelerating from a stop. If I’m sitting still, I’ll turn the key to full off, give it about 30 seconds, and it’ll start right back up. For whatever reason just re-starting without turning off never seemed to work.

So since it stalled on the highway and I wasn’t able to get it started at all, here’s the list I’ve replaced or completed:

  • main relay
  • fuel filter
  • plug wires
  • spark plugs (the old ones were due, but not overdue, and all four were pretty fouled with burned oil and had oil in the wells)
  • spark plug well o-rings and valve cover gaskets
  • and fully charged the battery

At this point, if I let it sit until it’s cool, it’ll start right back up with no trouble. Then once it warms, it starts to run a bit rough, eventually chugs, stalls, and then I can’t get it started again - spins a few times, then kinda sticks, then spins a few times, and kinda sticks again.

Any ideas??

2

The problem might be with the Idle Air Control valve.

https://www.rockauto.com/catalog/moreinfo.php?pk=931952&cc=1168433&jnid=409&jpid=0

The IAC valve controls the engine idle speed whenever the accelerator is released.

These IAC valves can be effected heat and fail to go the proper position for the idle condition and cause the engine to stall.

The next time the engine stalls and won’t start, slightly step on the gas pedal and then try starting the engine.

If the engine starts and continues to run as long as you have your foot slightly on the gas pedal, indicates a problem with the IAC valve.

Tester

3

This is a mystery. One idea, on some car the fuel pump will run when you first turn the key on to charge the fuel rail. Maybe something is causing the fuel rail to run dry, and the only way to get it charged again is to turn the key off, then back on.

Check the fuel pressure regulator vacuum hose. Do you see any fuel in that hose where it connects to the fpr? There shouldn’t be any.

4

Check the injectors. The DX had a DPFI system which was little more than a glorified carburetor. It had one main and one auxiliary injector that plugged into the throttlebody throat instead of the better system used in the HF/Si motors which had one injector per cylinder. If an injector isn’t working right, you’ll get stalls like that because it chokes off the whole engine rather than just one cylinder.