So my 07 H3 was idling very roughly. I cleaned the throttle body thoroughly with almost no effect. From what I read I was thinking mass airflow sensor but since those are over $100 & the H3 was over 80K miles I decided to try a new set of plugs first.

I ordered a set of exact OEM replacement plugs from Amazon for less than $30. Putting them in was probably the easiest plug replacement of any vehicle I have owned. You do have to remove the air resonator box to access the plugs but then it's just one bolt to remove the coil assembly & pull the plug.

The rough idle went away immediately but the I5 ran sluggishly for about the first 5-10 miles. I am assuming the computer was adapting to the new plugs and readjusting. I will be interested to see if I get a slight mileage improvement over the next couple of tankfuls.

 

How many miles are on your 07? Just for reference I was wondering what was the gap on the plugs you removed? Do you have pix of the old plugs?

Glad to hear your H3 is running better now!

 

I was right at about 83K miles. I didn't measure the gap since I was told the iridium plugs are not to be gapped, but I can probably get some pics of a couple of the plugs.