Skip the auto shop - Our mechanics make house calls

Q: misfire and high idle when hot

asked by on

so I replaced a blown head gasget and now I know I timed it correctly but I put it back together and now I am getting check engine code p0300,p0301,p0303 when hot and cold the code goes away when hot I see white smoke out of the muffler and it smells of burnt oil and idles at 2000rpms and has a missing fire sound after I gun it for a bit. when warm or cold no misfire and 800rpm idle. I checked the pcv valve and it is fine. its not getting hot. idk what to do? thanks

My car has 207000 miles.
My car has an automatic transmission.

A: You should have a compression test and cyli...

You should have a compression test and cylinder leakage check done on the engine to see if one or more cylinders have low compression, or is leaking compression somewhere. Check that all of the spark plug wires and injector wires are put on to the correct cylinders. Since the problem is with cylinder numbers 1 and 3 it's possible that you have the wires crossed.

Did you replace the oil and filter after the head gasket was replaced? If the rings are stuck or sticking it would explain the engine running better after revving a couple of times. A certified mechanic can inspect your vehicle to diagnose your Check Engine Light codes and find the right fix for your misfire.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Save up to 30%

Get a quote

What others are asking

Q: Self-installed axle not spinning.

When installing new axles there a some things that can go wrong, but if the axle is completely inserted into the transmission then the transmission should be fine. If you run the car and are getting power to only one...

Q: Fan not working

The most common problem is the cooling fan switch located on the pipe that connects the upper radiator hose to the radiator in the engine compartment. Another issue is that there may not be sufficient coolant in the radiator. I...

Q: I have issue with my Honda City 2004 Car AC

The problem sounds like you may be having an A/C clutch cycling out due to being low on Freon. Another possibility is that the system is overcharged and is putting a large load on the engine, and then kicks out...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
P2428 OBD-II Trouble Code: Exhaust Gas Temperature Too High Bank 1
P2428 code definition A P2428 trouble code signifies that the PCM has detected a problem in the exhaust gas temperature sensor circuit in bank 1, which subsequently contains the number one...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.