Skip the auto shop - Our mechanics make house calls

Q: high idle when hot and missfire all the time.

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 I see white smoke out of the muffler and it smells of burnt oil and idles at 2000rpms and has a missing fire sound. when cold not as often misfire sound 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.

If you overheated the engine prior to replacing the head gasket you would need to have the head checked for cracks and get the surface refaced. If this has been done, then the problem may be that the cylinder block is cracked, or you have not put something together properly and have a vacuum leak. The left over coolant in the exhaust from the previous overheating may be the reason for the smoke which will eventually go away.

Check the cooling system and engine for overheating again, if so, then you will need to find where the coolant is getting into the cylinders. A certified mechanic would be able to diagnose the symptoms you’ve described to in order to fix your misfire and high idle issues.

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: My cars rpms shot up to 7000 when started! Seemed possessed. I cut engine, started again, same thing. I tried letting out clutc

The first thing to check is to look at your gas pedal to see if the carpet mat is holding the pedal down. If it is then secure it away from the pedal. If the throttle is not held open...

Q: Car won't accelerate after 10 miles

Hello. It is more likely that the cause of this problem is that the catalytic converter is clogged which would cause the car to not to accelerate once becoming warm. There could also be a problem with the transmission. Your...

Q: Tires are vibrating

The tires would need to checked to see if any damage to the tires is found and if the tires are properly balanced. If you added any tire sealer to a tire to try and seal a leak, then the...

Related articles

P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...
Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...