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.

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・Fair and transparent pricing

Get a quote

What others are asking

Q: Smoke from engine and exhaust

This is very likely due to a leaking valve cover gasket. When a valve cover gasket leaks oil, the oil will land on the hot exhaust and burn. This is what causes the smoke. In severe cases, the engine may...

Q: How do you properly install and use floor mats?

Floor mats provide your car’s carpeting with an extra layer of protection from dirt, mud, and wear and tear from your shoes. If the carpet wasn’t protected by a floor mat, it would wear down very quickly. However, there are...

Q: RPM gauge goes from 5K to 2K - 2005 Nissan Maxima

Hi - it seems unlikely that a major drop in RPM during a shift is torque converter clutch lockup - 5K to 4K might be more reasonable. This behavior seems more like an upshift that is missing a gear -...

Related articles

How Long Does a Distributor O Ring Last?
The distributor is part of the ignition system in your vehicle and its purpose is to route high voltage from the ignition coil to the spark plug. The spark plug then...
How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.