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

asked by on April 24, 2016

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.

Engine is misfiring Inspection $94.99 - $114.99 Get a Quote

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.

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


Experienced Mechanic?

Earn up to $70/hr

What others are asking

Passenger side floorboard getting wet in rain.
Hello, if the car has a sunroof that's where I would start. This would require two people to perform a proper diagnosis. Using a garden hose you would run across the top of the car and look for a leak....
Car vibrates when stopping.
Your problem is a common one. The vibration/pulsation you feel when braking is possibly due to warped rotors. Rotors are a smooth machined metal surface that your brake pads make contact with when you apply your brakes. When the rotor...
Engine is knocking
Have you checked your oil level lately? Many times low oil level causes low oil pressure. Low oil pressure will make the engine knock because the oil is not lubricating the engine. If this happens for long enough it can...
Sparkplug wires melting in sparkplug socket.
From what you've described, the cylinder head overheated which caused the wires to melt. Your engine is overheating and the white smoke from the exhaust (https://www.yourmechanic.com/services/smoke-from-engine-or-exhaust-inspection) indicates that the head gasket is blown or cracked. You should have the car...
What would make antifreeze come out of a tail pipe after a water pump was replaced?
Hello. If there is antifreeze coming from the tailpipe then there is a serious issue with the engine. A water pump replacement would not cause this to occur. This means that coolant is entering the engine and it making its...
Engine won't crank to start.
Even if the shift interlock solenoid (https://www.yourmechanic.com/article/symptoms-of-a-bad-or-failing-shift-interlock-solenoid) is faulty, as long as the gearshift is in the Park position, you should still be able to start the car. Once the engine is running, you just won't be able to shift...
How do you figure out which engine mounts actually need replacing?
With all most 200k miles you most likely have all four mounts needing replacement. The first thing to do is to physically look at each one and look for rips or tears in rubber, sagging or oil soaked. Once all...
The vehicle keeps turning off while driving. Hummer H3
Hello - the first task is to determine what problem codes (https://www.yourmechanic.com/question/intermittent-stalling-while-idle-or-driving-by-david-m) are being set here. This will guide diagnosis, and tell whether it's a fuel supply issue (fuse, fuel pump relay, or fuel pump itself), or possibly an electrical...
I have a 2002 buick rendezvous and I'm looking to possibly swap the 3400 for an lx9 3.5
The re-designed gasket (Fel-Pro, for example, in the aftermarket) for the lower intake manifold on this engine, and the revised installation procedure, provide a 100% effective resolution to the notorious leak issue that you are referring to. With regard to...

Related articles

A Buyer’s Guide to the 2012 Honda Civic
America’s America’s best-selling compact car, the Honda Civic has been around for nine generations now, and the 2012 models boast some very exciting features and upgrades. Including coupe and sedan styles, the Civic continues to be one of the most...
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 Top 5 Selling Cars in Connecticut in 2012
Connecticut Connecticut offers plenty of rain and its fair share of snow during the winter months, which means drivers need vehicles that can handle these conditions. Top selling vehicles in previous years have included the Toyota Camry, Corolla and the...