Difficulty starting, hesitates when gas is applied

The car had original parts when I purchased it. Since then, I had the 2bbl carburetor replaced with a 4bbl. I also installed a dual exhaust and replaced the intake manifold. I had the spark plugs replaced, along with the wires, coil, rotor and distributor cap. Afterwards, I've noticed that the plugs are being fouled. The plugs that are furthest and closest to the firewall on the driver's side, have been fouled out. Also, two inner plugs on the passenger's side are also being fouled out. Due to this, the car starts with difficulty. It also starts hesitating when I apply the gas peda
Experienced mechanics share their insights in answering this question :
Hello there, thanks for your question. You may have a few different things going on with your 1973 Pontiac Ventura. When you upgraded from the 2bbl to a 4bbl, you increased the amount of fuel the engine is getting. Given that you have added more fuel, it is likely the engine needs to be tuned and the timing needs to be adjusted. Alternatively, you could possibly have an intake leak. Either way the engine is running rich or oil is leaking onto the spark plugs. Considering having a certified automotive technician such as one from YourMechanic inspect your car issue and perform any repairs as needed.

How to Identify and Fix Common car Problems ?

Our sources include academic articles, blog posts, and personal essays from experienced mechanics :

Engine hesitation is one of the most noticeable symptoms of bad spark plugs and wires and a common engine problem.
Rough starts, hesitation and poor acceleration are all common symptoms of a bad spark plug. If a spark plug or multiple spark plugs are faulty, they will have trouble creating the spark that causes the ignition process in your vehicle.
Faulty spark plugs can cause the car to exhibit starting troubles. Worn out plugs does not produce sufficient sparks, which is needed for starting the engine. This results in the engine to stall and fail to start quickly.
Spark plugs that are dirty or worn out should be replaced soon because they also cause a delayed throttle response.
A worn-out mass airflow sensor can cause engine problems and ultimately engine hesitation. Transmission: If your car hesitates when accelerating, then this could be due to a transmission clutch slippage, which is usually caused by low or old transmission fluid.
An engine that is hesitating to accelerate is most likely dealing with a fuel/air mixture that is too lean. Engine`s that are running inefficiently will begin to show signs like hesitation which will only become worse over time.
Bad Sensors

One common culprit for this problem is the crankshaft position sensor, which measures the position and speed of the crankshaft. The computer uses the information from this sensor to know when to fire the spark plugs. If the sensor isn`t working, the spark plugs won`t fire, keeping the engine from starting.

If your car hesitates when accelerating at low speed, you likely have a lean air-to-fuel mixture—meaning the gas getting to your engine doesn`t have the correct mix of fuel and air.
When you press down the accelerator pedal and get minimal output, it could mean you have a problem with your fuel system. The most probable issue is a clogged fuel filter. Your fuel filter works to ensure that dirt and debris do not get into the fuel system.
A damaged spark plug wire may produce a rough idle from the engine. This is due to incomplete combustion and fuel burn at low rpm due to low or no voltage reaching the spark plug. This buildup of ab incomplete burn of fuel causes inconsistent combustion, resulting in the rough sound heard at idle.
A failing points and condenser system can cause rough running, misfires, lean and rich conditions. If the engine is difficult to start, and runs rough once it does start, then it is time to contact a mechanic to have a look at the system and find out exactly what the problem is.
If your car hesitates when you try to speed up at a low speed, it`s likely because the air and fuel ratio is too lean. A lean air-to-fuel ratio means the gas going into your engine doesn`t have the right amount of fuel and air.
A clogged or malfunctioning EGR valve can disrupt the vehicle`s air-fuel ratio, which can cause engine performance issues such as a reduction in power and fuel efficiency. The vehicle may also stall or hesitate while accelerating.
Hesitation. Your car hesitating when you accelerate is an issue that can be caused by transmission problems. It is possible for you to mistakenly think your gears are slipping when in fact it is your engine hesitating. It is also common to experience issues when switching from park to drive for transmission problems.
A rough idling engine can be caused by spark plugs or spark plug wires. Spark plugs use the electrical current received from ignition coils to ignite the air/fuel mixture within the combustion chamber. A plug that is damaged or installed incorrectly can result in fuel being burned at an inconsistent rate.
Poor Acceleration

A faulty knock sensor may not let the engine properly accelerate while driving on the highway, causing the car to lose fuel mileage (reduced fuel economy).

Yes. While the damage may seem small initially, the longer you drive with a bad oxygen sensor, the worse the damage will become. Eventually, you may experience rough idling, poor acceleration, engine misfires, an illuminated check engine light, and failed emission tests.
Car Will Not Start: Over time, as the camshaft position sensor fails, the signal it sends to the engine control module weakens. When the engine no longer receives the signal, you will not be able to start your car.
The crankshaft position sensor monitors the position and speed of the crankshaft and other parameters that play an important role when starting the engine. If the crankshaft position sensor is having a problem, the vehicle may have intermittent starting issues or not start at all.
The ignition control module is a solid-state switching device that controls the operation of the ignition coil or coils. It is a small, high-current circuit used to ground the negative side of the coil in order to build charge.
A faulty ECM can send poor data to your vehicle`s transmission control module (TCM). As a result, the vehicle cannot properly shift gears or apply power, causing the shift to feel awkward, delayed, or even jarring. When this occurs, the engine may sporadically become more active or stall out.
A manual vehicle experiencing this difficulty may be related to a slipping clutch. A good indication that this is the case is a softer resistance in the clutch pedal as well as loss of power and difficulty maintaining speed. Any of the issues above can cause your engine`s RPM to run high or jump inconsistently.
The most common cause of poor engine airflow is a clogged or damaged air filter. The air filter in your car protects the engine by catching all kinds of debris before it can enter the cylinder and cause more damage.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

Difficulty starting, hesitates when gas is applied – 1973 Pontiac Ventura
ANSWER : Hello there, thanks for your question. You may have a few different things going on with your 1973 Pontiac Ventura. When you upgraded from the 2bbl to a 4bbl, you increased the amount of fuel the engine is getting. Given that you have added more fuel, it is likely the engine needs to be tuned and the timing needs to be adjusted. Alternatively, you could possibly have an intake leak. Either way the engine is running rich or oil is leaking onto the spark plugs. Considering having a certified automotive technician such as one from YourMechanic inspect your car issue and perform any repairs as needed.

Fuel pump engages. Batery good, alternator good volts, jump start helps when wont start. Temp does not matter. Intermittent?
ANSWER : Hello. Thank you for writing in. There are several reasons your vehicle may only start when jump starting. The first and most common is a build up of resistance that is causing you to need a boost of voltage to get the engine started. This may be due to poor battery cables, a bad ground connection, a poor starter solenoid, and a couple of other issues. The first thing you want to do is perform a visual inspection of the starting system. Make sure there is no corrosion build up in the battery cables. You can also check the resistance across these wires and make sure you have a solid connection between components. You then want to make sure the starter solenoid is doing its job. It is responsible for taking the small amount of electricity sent by the ignition and turning it into a huge electrical charge that is strong enough to push over the engine with the help of some gear ratios in its favor. Do some more testing, and stick to the basics before assuming its something seriously complicated.

Why doesn’t car start after running out of gas girlfriend ran gas out of car now won’t start plenty of gas in tank doesn’t sound l
ANSWER : Fuel pumps rely on liquid gasoline for cooling. Consequently, it is recommended to keep the fuel tank at least 1/4 full to prevent the fuel pump from overheating. If the pump is run to the point of being dry, the seal on the impeller can overheat and get damaged. Even if the pump subsequently runs, as you report your does, it cannot develop enough suction to pick up fuel due to the seal damage. That is possibly what has happened in your case but it should be confirmed prior to replacing the fuel pump. In your circumstance the recommended service is fuel pump replacement but if you request that, the responding certified mechanic will do enough tests to confirm that there is no other possible explanation for the failure. There is a quick and direct way to determine if the problem is lack of fuel. Procure a can of "starter fluid" from any department store. Using the material cautiously (it is highly flammable; keep away from flames or sparks), introduce some of the fluid into the intake of the engine while you engage the starter motor. If the vehicle starts and runs briefly, then you know for sure the problem is fuel starvation of course almost undoubtedly caused by the pump failing. Fuel pump replacement can be accomplished in the field, right at your location, if you desire that service.

2005 pontiac g6 won’t start unless I tap gas pedal and turn key to start at same time.. Also hesitates a bit while driving.
ANSWER : You may have a malfunctioning idle air control valve. By holding the throttle open manually by depressing the accelerator pedal, you are allowing enough air in for the car to start. If the fault is not the idle air control valve, there could be another issue in the air induction system. Inasmuch as the hard starting could be related to the hesitation issue I suggest you request a hard start diagnostic and the responding certified mechanic will get this resolved for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

Vehicle won’t start, once it’s jump started it only stays running until you turn it off, then it work start again without jumping.
ANSWER : Hi there. There could be two problems here. It is possible that your battery is bad and will not take a charge from your alternator while driving. In that case every time you shut your car off you will not have enough juice to start it again. Inspect your battery – it should have at least 12.5 to 13 volts to start your car, if it doesn’t you will need to replace the battery. The second problem could be that your alternator is bad and not charging your battery, in this case you will need to replace your alternator. Both the battery and the alternator can be tested in your car. If you would like to have the car checked for you, a certified professional from YourMechanic can come to your car’s location to diagnose the starting problem and proceed with repairs.

Saab 9-3 will not always start. Sometimes I have added gas and it started,also took air filter out then replaced and it started,
ANSWER : Hi there. When you have random issues like this, it tends to be caused by a restriction of fuel, air or an inability for the fuel injection system to effectively mix the air and fuel to be burned. This could be due to a clogged fuel filter, dirty air filter, EGR valve, mass air flow sensor or other fuel system component that is dirty. The turbo tends to add an additional five other possible issues to the list. SAAB’s tend to be pretty complex and should be examined by a SAAB specialist, however, it might be beneficial to have one of our mobile mechanics complete a car is hard to start inspection to see if they can pinpoint issues and recommend or complete the repairs needed.

I have trouble starting the vehicle every time I put gas in the car
ANSWER : As you may know, this issue is commonly related to the evaporative emissions (EVAP) system which is comprised of a few components, one of which you have already addressed, the purge valve. In some cases, when you have an air leak in the EVAP system, then the manifold absolute pressure (MAP) sensor will not be able to determine the air density, and the mass airflow (MAF) sensor will not be able to correctly determine the volume of air entering the engine. This will lead to an over-fueling or under-fueling situation depending on the size of the air leak and the engine’s operating speeds and load. This could eventually lead to destroying the catalytic converter as well. I would recommend having an expert technician, such as one from YourMechanic, take a look at your car to diagnose your starting and stalling problems.

I have a 2004 Buick Rendevouz that doesn’t want to start. At first, it had a hesitation problem and it died at low rp
ANSWER : The camshaft position sensor will make the engine run but poorly. Check the crankshaft position sensor to see if its damaged or unplugged. A damaged crankshaft position sensor will cause a no spark condition. If you need further assistance with your engine not starting after a tune-up, then seek out a professional, such as one from Your Mechanic, to help you.