Engine Hunts at Start and Then Rough Idle When Warm

[lazabby]

Is it set to 4 cylinder mode?

Yes.

https://youtu.be/8Ca4UV654cE

[lazabby]

Hey Shannon, when I was doing some dwell meter/mixture setting troubleshooting and fine tuning, it did the same thing where it stayed at one reading instead of fluctuating and also tended to settle in after running for a few minutes. In my case, it turned out to be a bad O2 sensor.

I didn't manage to get my own O2 sensor out and replaced, so I took it to a shop I've used in the past and he got it out, replaced it and then set the dwell properly. Idle and fuel mileage has been good ever since.

I'm sure there is a more technical or scientific explanation as to what happens with that circuit when the O2 sensor fails to cause it to stay steady or not fluctuate or whatever. I don't have that explanation, but also figured I didn't need it after a new O2 sensor in my car fixed it all up anyway.

I couldn't get your youtube video to play by the way. It was marked as private.

Jonathan thanks. That's what I'm suspecting. I'll probably replace it.

Thanks for letting me know the setting on the video. Didn't know it was marked private.

[Jonathan]

You can also double check the O2 sensor reference ground wire is still connected properly. It is the one which grounds to the block under the air filter housing, pretty much in the far corner passenger side and towards the front of the car. You can identify it fairly easily because a couple inches of the ground wire has a red wrap on it. The wire is only six inches or so long and the free end has a black quick connector (very similar to the ones used on the ballast resistor connections). The other end of that wire ultimately connects with the ECU behind the driver's seat. It could be another wiring connection that's not making good contact or not connected at all perhaps. And easy enough to check.

O2 sensor ground.jpg

My photo is slightly misleading as I had to relocate mine since the hole it's meant to go into had a broken off screw in it. The red arrow points to the hole your red ground wire is probably screwed into.

[lazabby]

You can also double check the O2 sensor reference ground wire is still connected properly. It is the one which grounds to the block under the air filter housing, pretty much in the far corner passenger side and towards the front of the car. You can identify it fairly easily because a couple inches of the ground wire has a red wrap on it. The wire is only six inches or so long and the free end has a black quick connector (very similar to the ones used on the ballast resistor connections). The other end of that wire ultimately connects with the ECU behind the driver's seat. It could be another wiring connection that's not making good contact or not connected at all perhaps. And easy enough to check.

O2 sensor ground.jpg

My photo is slightly misleading as I had to relocate mine since the hole it's meant to go into had a broken off screw in it. The red arrow points to the hole your red ground wire is probably screwed into.

The ground is there. I replaced the O2 sensor but I'm still getting a reading between 10.5 and 11 on the dwell meter at 4 cylinder. You can see it on the video. What's going on? The car still hunts a little when starting but smooths out when warm.

[opethmike]

The ground is there. I replaced the O2 sensor but I'm still getting a reading between 10.5 and 11 on the dwell meter at 4 cylinder. You can see it on the video. What's going on? The car still hunts a little when starting but smooths out when warm.

What do you get with the sensor unplugged?

[Jonathan]

What do you get with the sensor unplugged?

Mike's thinking the same thing I was... to confirm what you get for each of the troubleshooting steps:

Dwell troubleshooting.jpg

[lazabby]

Mike's thinking the same thing I was... to confirm what you get for each of the troubleshooting steps:

Dwell troubleshooting.jpg

I'll try it with the sensor unplugged. Might take a day or two to get back with a response.

[Bitsyncmaster]

What do you get with the sensor unplugged?

That number is saying your mixture is pretty far off. The ECU has maxed out it's adjustment range. Move your mixture screw a little bit one way or the other and see if that number changes.

[opethmike]

That number is saying your mixture is pretty far off. The ECU has maxed out it's adjustment range. Move your mixture screw a little bit one way or the other and see if that number changes.

I am thinking the same thing.

Shannon, any chance you can get a hold of a wideband O2? That could aid quite a bit.

[Morpheus]

Lean it out a bit and see if it changes.