Rough vibration with codes

[skyworker]

The Car: 96' LSi 110k

The History:
1) A few months ago I had a CEL. Went to Auto Zone they checked the code it was the O2 sensor bank 1 sensor 2. (passenger side pre-cat, I think?) There was an exhaust leak at the gasket before the cat which I fixed but the CEL came back. - Tried to check the voltage on the sensor, I didn't get the correct voltage and decided it was a bad sensor. The car was running fine so I didn't do anything about it.

2) A few days ago, the car started shaking in over drive with light acceleration while tiring to maintain speed. It also shakes at idle in park/drive/neutral. If I accelerate fast or coast it's fine. Only at idle or slight acceleration does it shake. The CEL went from on to flashing. Had AZ check the codes again. 1) O2 sensor B1 S2, heater circuit. 2) O2 Bank 1 Sensor 2, slow response. 3) #4 misfire.

3) I ran a bottle of injector cleaner through it with no results. Found a frayed wire going to front passenger side injector at the connection. Cut the frayed part off and soldered the wire back to the connector. It didn't change anything. Also, the gas millage has dropped, I don't have the numbers, but my guess is it went down by 30%.

My Theory:
A faulty passenger side pre-cat O2 sensor. A faulty coil on the #4 cylinder causing a misfire and the driver side pre-cat O2 sensor to register a code.

The Plan:
Pull the injector wires off one at a time to try and locate misfiring cylinder. I expect it to be the #4 (middle driver side, I think?). Remove and inspect the coil. Swap it with one of the other coils and see if the problem follows the coil or stays with the cylinder. If it follows the coil replace the coil. Replace the passenger side O2 sensor.

The Request:
I'm not a mechanic and haven't done anything to the SVX since I've had it, except change the oil and fix an exhaust leak. Let me know if I'm on the right track here, if there's anything I might be missing, should look for, or any advice on the repair. I plan on working on it tomorrow after work. Thanks.

[Wikedjuggalo]

Originally Posted by skyworker

The Car: 96' LSi 110k

The History:
1) A few months ago I had a CEL. Went to Auto Zone they checked the code it was the O2 sensor bank 1 sensor 2. (passenger side pre-cat, I think?) There was an exhaust leak at the gasket before the cat which I fixed but the CEL came back. - Tried to check the voltage on the sensor, I didn't get the correct voltage and decided it was a bad sensor. The car was running fine so I didn't do anything about it.

2) A few days ago, the car started shaking in over drive with light acceleration while tiring to maintain speed. It also shakes at idle in park/drive/neutral. If I accelerate fast or coast it's fine. Only at idle or slight acceleration does it shake. The CEL went from on to flashing. Had AZ check the codes again. 1) O2 sensor B1 S2, heater circuit. 2) O2 Bank 1 Sensor 2, slow response. 3) #4 misfire.

3) I ran a bottle of injector cleaner through it with no results. Found a frayed wire going to front passenger side injector at the connection. Cut the frayed part off and soldered the wire back to the connector. It didn't change anything. Also, the gas millage has dropped, I don't have the numbers, but my guess is it went down by 30%.

My Theory:
A faulty passenger side pre-cat O2 sensor. A faulty coil on the #4 cylinder causing a misfire and the driver side pre-cat O2 sensor to register a code.

The Plan:
Pull the injector wires off one at a time to try and locate misfiring cylinder. I expect it to be the #4 (middle driver side, I think?). Remove and inspect the coil. Swap it with one of the other coils and see if the problem follows the coil or stays with the cylinder. If it follows the coil replace the coil. Replace the passenger side O2 sensor.

The Request:
I'm not a mechanic and haven't done anything to the SVX since I've had it, except change the oil and fix an exhaust leak. Let me know if I'm on the right track here, if there's anything I might be missing, should look for, or any advice on the repair. I plan on working on it tomorrow after work. Thanks.

To replace an O2 drive said car on ramps and its pretty easy. Autozone has the "free rent-a-tool" and specifically the tool for 02 sensors. I know because I used it they gave me a case with a few size in it. I'd replace the O2 sensor first and then go to see about misfiring.

[svxistentialist]

Plus 1

The sensors lead a hard life. When they send a signal to the ECU that is out of expected range, the fuel map can start to do a lot of strange things to keep the engine working in the sweet zone. Generally leads to poor running.

Change the O2 sensor first. Your problems may all go away.

Joe

[skyworker]

Update:
I replaced both O2 sensors with no change in the performance. I did find that I am only running on 5 cylinders. I unplugged the injector on #4 and the idle didn't change. When I did that to all the other cylinders it started to die.

[svxistentialist]

Then follow the logic of your theory. Bad coil on #4. The coils have three different lengths of wire, short, longer, longest.

They can be bad without seeing any obvious breaks or cracks. Remember they run at very high tension [voltage]. As they age the insulation breaks down and sparks leak to the engine block.

You may be able to see this if you run the engine in a dark garage. Don't smother yourself with carbon monoxide. The insulation break could be in the cable from the igniter, but this is less likely because it is low tension. The spark leak is more likely after the coil has boosted the voltage.

If you verify the spark leak to the block, my preferred cure would be to buy a new coil rather than one from a scrap car. They are relatively expensive items, but if the insulation has started to break due to age and heat, no point buying an old one that has the same ageing under its belt.

Best of luck with it.

Joe

[skyworker]

Update:

I replaced the coil pack on the #4 cylinder. The CEL went away along with the vibration. Thanks for the help.

[svxistentialist]

That's great news.

Glad you got her sorted.

Joe