Skip the auto shop - Our mechanics make house calls

Q: Engine shakes when I turn on the car for the first time in the day

asked by on

My Pontiac G8 engine shakes every time I turn it on for the first time in the morning but after that the engine doesn't shake any more. I changed the spark plugs but the engine light came on it had come up a few weeks back but I cleared the code disconnecting the battery. Now the check engine light came up again? And the engine still shakes when I turn it on?

My car has 89000 miles.
My car has an automatic transmission.

A: Hi, thanks for writing in. I'd be happy...

Hi, thanks for writing in. I'd be happy to provide my insight.

Most likely the fuel pressure is dropping off as it sits overnight. This is a fairly common problem. I'm wondering what the code that was being set was. I would think it would was a random misfire code with this condition though. When the fuel pressure drops as it sits, your motor will take extra time to build fuel pressure. You can test this theory by cycling the key several times before you attempt to start it. Each time you cycle the key, leave it in the run position for at least five seconds, then turn it off. The fuel pump will only run for a few seconds if the motor is not started. Many GM vehicles won't turn the fuel pump on for as much as a minute after the first key cycle. If you turn the key on an listen for a pump noise coming from the fuel tank, you can confirm it the pump is turning on.

If this makes your car start better in the morning, the next thing to do is locate the source of the internal fuel pressure leak. It will either be in the fuel tank, a fuel injector or the fuel pressure regulator. Although, if it is the regulator, the car will always run very rich, most likely spewing black smoke out the tail pipe.

This is by far the most likely cause for your problem. Anything else will require an experienced technician to diagnose your car as it will not be an obvious problem requiring the use of sophisticated equipment and extensive knowledge of all the car systems. For this reason I recommend the following inspection to help you figure this out: Car is hard to start inspection

If your car does have a loss of fuel pressure, it will take some diagnosis to determine where the pressure loss is occurring. This is usually a creative process that will be specific to your car. I hope this helps and best of luck!

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

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: Hello. On 08 pontiac g8 do I have to replace the whole thermostat housing if is leaking or could just get seals and change thermo

Hi there: Today's OEM parts are made to be cost-effective as opposed to help mechanics fabricate repairs to be honest with you. So, it's probably a good idea to replace the entire housing for a few reasons. First, the thermostat...

Q: Engine shakes after 10psi.

Check for problem codes anyway, even if the Check Engine light is not illuminated. There may be a transient code for a misfire. I would suspect that either the plugs or coils are failing under load, and need to be...

Q: AC melting vents.

An overall test of your air conditioning system would be helpful it sounds like the either the compressor isn't cycling refrigerant for some reason probably a leak in the system somewhere, a certified mechanic would be able to find the...

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...
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...
P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the P0052 code means This code is seen when the Engine Control Module (ECM) tries to control the...