Q: 07 Honda Fit Code PO420. Car missing at idle when AC is on and has trouble accelerating, especially up hills, more so with AC on

asked by on June 29, 2017

07 Honda Fit with a OBD II code PO420. Car misses at idle when AC is running. Car hesitates on acceleration especially when the AC is on. Car lacks power going uphills especially with AC on and even more so on very hot days.

My car has 310000 miles.
My car has a manual transmission.

Engine is misfiring Inspection $79.99 - $99.99 Get a Quote

Hi there.The catalytic converter has two oxygen sensors. One oxygen sensor is positioned in front (upstream) of the catalytic converter and the other oxygen sensor is positioned at the rear (downstream). If the upstream oxygen sensor is working properly, its readings should fluctuate from when the car is at operating temperature and when running in a closed loop. When the oxygen sensors have readings that are similar to each other, it is an indication that the catalytic converter is not working as intended. If the voltage of the downstream oxygen sensor decreases, and begins to fluctuate like the upstream oxygen sensor, it means that the oxygen levels are too high and the Powertrain Control Module (PCM) will store the P0420 trouble code. This could be caused by a cracked exhaust manifold, damaged sensors or catalytic converter or electrical harness that controls the the sensors. It would be a good idea to have a professional mechanic complete an engine is misfiring inspection.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

What others are asking

To check the transmission oil on my pontiac g6 do it has to be running, it dosent have a dipstick so i have to take out the bolt

You have to have the engine running on a lift or a flat surface before you take out the check plug or else the fluid will spill out. Then you can check the fluid level and put the plug back...

How do I check the oil?

Keeping an eye on vital fluids is part of being a responsible car owner. One of the most important (and most easily checked) fluids is engine oil. To check it, just follow these simple steps: Turn off the engine...

Crank but no start and there is no fuel pressure.

Hi there. Check the fuel pressure regulator on the fuel rail. The regulator will adjust the fuel flow and adjust the pressure. If the regulator is working, then there may be a restriction in the fuel line. Remove the fuel...

What is this part

Hi Tyler. It's very difficult to determine a part name without seeing it. Unfortunately, since we can't have images attached through this platform, it's also hard for us to review it. One thing you could do perhaps is to take...

Loud engine noise

If you are hearing a rattling noise on start up and for a couple of minutes that then goes away, then the variable valve timing actuators are at fault. The manufacturer is working on a replacement now, and will issue...

Transmission shifting

Hi. It's very possible that the source of your problem is related to the transmission control module. In some cases, the sensors inside the transmission will fail to send signals to the TCM and cause the problem you're experiencing. It...

Can my antifreeze leak be linked to my transmission problem?

Hi there. You will need to first find the coolant leak and address the leak and get it fixed. The engine may overheat and cause even more problems. The transmission or engine misfires could be from the coolant leak if...

New battery. Car won't start until minutes later when attempted again.

A voltage test will not reveal whether the battery is defective or not. A different test, referred to as a "load test", is required. During these no start incidents, check to see if the engine immobilizer system (security system) is...

How does the security system work in a 2012 Honda Accord?

If your Accord has a security system as a standard feature (all but LX models), you have built in anti-theft protection. The system is designed to flash the lights and honk the horn if someone tries to enter the vehicle...

Related articles

The Best Used Cars to Buy for Families
If If it’s time for you to search for the top used cars specifically for families, check out the list we’ve put together of the top five. The list of must-haves Typical items that families are looking for in their...
The Best Used Cars to Buy For Fuel Economy
Saving money on gas is an important factor to consider when buying a car. The Honda Civic, Toyota Prius, and Ford Fusion all have great fuel economy.
The Best Used Cars to Buy If You Love Camping
Do Do you love camping, getting back to nature and enjoying life in the great outdoors? If you do, then you know that getting there can be half the fun, and it’s even better if you have a great ride....