1989 Integra LS 5-speed; 164k milies; rebuilt motor at 148k miles; tune-up just performed (cap, rotor, plugs, wires, air filter, pcv valve); runs very well - except idle at startup. No codes thrown.

When engine is cold, the engine starts quick and I am ready to go. BUT, the idle when cold is quite erratic with the needle bouncing up and down and I can feel the motor doing the same. However, after the engine warms up, it goes away. It fact, as it is warming up (after mile or so) the situation slowly improves.

Has anyone experienced an O2 sensor causing this symptom? Could it be the Electronic Air Control Valve?

 

If the 02 sensor is getting lazy that will happen when it is cold. Once it heats up it gets a little less lazy, but still has a problem. Eventually it will be like that the whole time. You can a universal 02 sensor for an 89 at autozone for like 45 bucks.

 

Great response! Have you experienced this problem?

 

Yes. I used to own an 89 w/a zc swap and I have had just about every problem one could have with that car.

 

Good information. However, I did read in another posting that the O2 sensor does not affect the system until after it is warmed up.

 

OBD 0 1 OR 2?

 

Additional information:

Car starts when cold normally with idle about 2000 rpm and after a few seconds it drops to about 1500 rpm until warmed up when it drops to about 800 rpm. However, if car is driven when cold, the rpm needle bounces erratically when at idle. You can feel the rpms changing. It has never done this before. Then it will gradually improve as the engine warms and the problem does not exist once engine is warmed up after several miles.

 

Replace the modulator in the distributor.

 

That is a very direct answer!! Seems that you have seen this before. Yes?

Now, I must figure out what this part is!

 

You have to take the distributor out and dis assemble it. The modulator looks like a black ms-shaped square with about 5 prongs coming off of it and is secured to the inside of the dis. w/screws..