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Mike V.
Mike V., Mitsubishi Mechanic
Category: Mitsubishi
Satisfied Customers: 24035
Experience:  25 years experience on all makes and models. Nissan and Subaru factory trained.
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2008 mitsubishi endeavor missing, Yes. Fixing yourself. What

Customer Question

2008 mitsubishi endeavor missing
JA: Are you fixing your Endeavor yourself? What have you tried so far?
Customer: Yes. Fixing yourself. What I have done so far is replace the oxygen sensor on bank 1 upper. It then drove fine and I thought it was done. Now it is donig it again
JA: Have you located all of the vehicle's oxygen sensors? Are the wires leading to and from each intact and in good shape?
Customer: The ignition coil has a crack around the bolt hole that holds it down. Should I replace it?
JA: Anything else you want the mechanic to know before I connect you?
Customer: Should we replace all oxygen sensors? All 4. I just replaced one
Submitted: 2 months ago.
Category: Mitsubishi
Expert:  Mike V. replied 2 months ago.

Hello and thank you for your question!
My name is ***** ***** I will be assisting you today.Please give me a moment to type my response. Thanks

Expert:  Mike V. replied 2 months ago.

No need to request a phone call, but please give me a moment to type my response.

Expert:  Mike V. replied 2 months ago.

Is the check engine light on or flashing when the engine is running?

Customer: replied 2 months ago.
Check engine light is on
Customer: replied 2 months ago.
I do not want to pay for a call
Customer: replied 2 months ago.
The code PO421
Expert:  Mike V. replied 2 months ago.

Ok

Before replacing the coil or any other part of the ignition system, run this test.

With the engine running at idle take a spray bottle and fill it with water, then spray water on the wires and coil. Normally if any of the ignition parts are bad, then you will see sparks arcing. Then replace the part and it should clear up.

If nothing arcs, then it's best to have the codes read so you know which cylinder is actually misfiring and you can repair that.

Ok, since you have a p)421, this is a converter code and it can be caused by the misfire, so do not replace the converter until you have the misfire cured, then erase the codes and see if it comes back.

Please let me know what more I can do to assist you today. Also, please remember to rate my answer, Just Answer does not compensate me for my time and resources. Follow up questions are included in the price of your question. If you are using the free trial, or have a subscription a rating is still required.
Thank you so much!

Customer: replied 2 months ago.
what you are saying is the ignition could be causing the problem. So fix that first.
Expert:  Mike V. replied 2 months ago.

Yes, because if you have a misfire, then raw fuel is going into the converter. It can't clean it all out, so the O2 sensor will tattle on the converter and that's your P0421.

That being said, it IS possible the converter is bad, but I would take care of the misfire for the above reason. Get all the gas burning before it goes into the converter and you might just find the converter isn't a problem.

Expert:  Mike V. replied 2 months ago.

Please let me know if there is anything else I can do to help.
Also, please remember to rate my answer.
Thanks so much!

Customer: replied 2 months ago.
Thank you
Expert:  Mike V. replied 2 months ago.

You are very welcome!!

Please let me know if there is anything else I can do to help out.

Customer: replied 2 months ago.
Sprayed water and nothing. No sparks. What should I do next. Should I replace the oxygen sensors?
Customer: replied 2 months ago.
I checked the spark plugs. They look fine.
Expert:  Mike V. replied 2 months ago.

Inspect the boots on the ignition coils. Make sure none of the coil boots have any arc marks on them.

Also, with the engine running you can check for a vacuum leak by spraying some carb cleaner along the intake manifold.

I would not replace the O2 sensors on it at this point. I don't think they will resolve anything to be honest.

Customer: replied 2 months ago.
We have individual coil packs not wires
Expert:  Mike V. replied 2 months ago.

I understand, but if spraying the coil didnt show any arcing, under the coil is the boot that sits over the spark plug. If it's arcing inside the cylinder head, you won't see spark with the water test. You have to inspect them and look for burn marks.

I would start with bank 1 because that's where the converter code is.

Bank 1 is the rear pain in the butt bank of course, but I suspect that's where the issue is since the code is for the bank 1 converter.

Expert:  Mike V. replied 2 months ago.

Do you need further assistance with this?