Friday, 24 November 2017

ON-BOARD DIAGNOSTIC SYSTEM GENERATONS

by on November 24, 2017

ON-BOARD DIAGNOSTIC SYSTEMS

Because all manufacturers have continually updated, expanded, and improved their
 computerized control systems, there are hundreds of different domestic and
import systems on the road. Fortunately for technicians, OBD-II called for all vehicles to
 use the same terms, acronyms, and definitions to describe their components.
They also have the same type of diagnostic connector, the same basic test sequences, and
 display the same trouble codes. OBD-II began in 1996 and has been on all vehicles sold
 in North America since 1997. The primary goal of OBD systems is to reduce vehicle
 emissions and reduce the possibility of future emission increases by detecting and reporting
system malfunctions.

OBD-I (On-Board Diagnostic System, Generation 1)


OBD-I systems were first used in 1988. The ECM was capable of monitoring
 critical emission-related parts and systems and illuminate a malfunction
 indicator if a defect was found. The malfunction indicator lamp (MIL) was in
 the instrument panel. Most OBD-I systems used flash codes to display DTCs.
The codes were displayed with the MIL. Often, the codes were displayed by
 jumping across terminals at a diagnostic data link connector (DLC). Manufacturers
provided lists of what the codes represented, along with step by- step diagnostic
procedures for identifying the exact fault.
         Typically, the DTCs represented problems with the sensors, fuel metering system,
 and the operation of the EGR valve. If any of these were open, shorted, had high
resistance, or were operating outside a normal range,a code was set. The MIL not only
 helped with diagnostics, but also alerted the driver that there was a problem. The MIL
 would turn off when the condition returned to normal; however, the DTC remained in
memory until it was erased by a technician. OBD-I was a step in the right direction, but
 it had several faults. It monitored few systems, had a limited number of DTCs
 (these were not standardized, so each manufacturer had its own), and allowed a limited
use of serial data; most manufacturers required a specific scan tool and procedure, and the
names used to describe a component varied across the manufacturers and their model vehicles.

OBD-II (On-Board Diagnostic System, Generation 2)



OBD-II was established to overcome some of the weaknesses of OBD-I.
This was possible because of the advances made in computer technology and was
necessary because of stricter emissions standards. OBD-I systems monitored only
a few emission-related parts and were not set to maintain a specific level of emissions.
OBD-II was developed to be a more comprehensive monitoring system and to allow more
accurate diagnosis by technicians. Studies estimate that approximately 50% of the
total emissions from late-model vehicles are the result of emission-related problems.
 OBD-II systems are designed to ensure that vehicles remain as clean as possible over
their entire life. During an emissions or “smog” check, an inspection computer can be
plugged into the DLC of the vehicle and read the data
from the vehicle’s computer. If emission-related DTCs are present, the vehicle will fail the test.
OBD-II added monitor functions for such things as catalyst efficiency, engine misfire detection, evaporative system, secondary air system, and EGR system flow rate. These monitors detect problems that would affect emissions levels. Also, a serial data stream of twenty basic data parameters and common DTCs was adopted. OBD-II systems monitor the effectiveness of the
major emission control systems and anything else that may affect emissions and will illuminate
the MIL when a problem is detected. During the monitoring functions, every part that can affect emission performance is checked by a diagnostic routine to verify that it is functioning properly. OBD-II systems must illuminate the MIL if the vehicle’s conditions
allow emissions to exceed 1.5 times the allowable standard for that model year based on a federal
test procedure (FTP). When a component or strategy failure would allow emissions to exceed this level and the fault was detected during two consecutive trips.


Data Link Connector


Pin 1: Manufacturer discretionary
Pin 2: J1850 bus positive
Pin 3: Manufacturer discretionary
Pin 4: Chassis ground
Pin 5: Signal ground
Pin 6: Manufacturer discretionary
Pin 7: ISO 1941-2 “K” line
Pin 8: Manufacturer discretionary
Pin 9: Manufacturer discretionary
Pin 10: J1850 bus negative
Pin 11: Manufacturer discretionary
Pin 12: Manufacturer discretionary
Pin 13: Manufacturer discretionary
Pin 14: Manufacturer discretionary
Pin 15: ISO 9141-2 “L” line
Pin 16: Battery power

 OBD-II standards require the DLC to be easily accessible while sitting in the driver’s
seat . The DLC cannot be hidden behind panels and must be accessible
 without tools. The connector pins are arranged in two rows and are numbered consecutively.
Seven of the sixteen pins have been assigned by the OBD-II standard. They are used for the
 same information, regardless of the vehicle’s make, model, and year. The remaining nine pins
can be used by the individual manufacturers to meet their needs and desires. The connector is
 “D”-shaped and has guide keys that allow the scan tool to only be installed one way.
Using a standard connector and designated pins allows data retrieval with any scan tool
designed for OBD-II. Some vehicles meet OBD-II standards by providing the designated DLC
 along with their own connector for their own scan tool. Often a vehicle will have more than
one DLC, each with its own purpose. Due to OBD standards, the OBD DLC will always be
 located within a foot, to the right or left, of the steering column
foot, to the right or left, of the steering column.

Friday, 17 November 2017

QUICK LOOK INTO AN ANTI-LOCK BRAKE SYSTEM

by on November 17, 2017
WHAT IS AN ANTI-LOCK BRAKING SYSTEM?
          This is an automobile safety system that allows the wheels in a motor vehicle to maintain traction with the road surface according to the drivers input while braking, preventing the wheels from locking up and avoiding uncontrolled skidding also it reduces braking distances, although it still improves vehicle stability control.
abs imageWHY IS THE ANTI-LOCK BRAKE SYSTEM IMPORTANT?
       STOPPING ON ICE;  As mentioned above an ABS system prevents lock ups and skidding even in a slippery road or condition. This system has been proven to save lives a whole lot of time as it assists the driver to be in control of the vehicle.
       TRACTION CONTROL;  An ABS system most time houses the traction control system or sometimes share some of the infrastructure of a traction control system, where new technology has seen that each wheel has adequate traction on the road. That makes it easier for manufacturers to install both features at the factory.
     VEHICLE STABILITY  CONTROL SYSTEM; An ABS system works together with the VSC system to help see that the vehicle doesn't skid away while making a turn or while slowing down.
      HIGHER RESALE VALUE;  As a feature in a vehicle, the ABS raises the market value of a particular vehicle. Especially nowadays where this system has become a standard in many vehicles, not having could affect resale price drastically.
                          HOW DO I KNOW IF MY CAR HAS AN ANTI-LOCK BRAKE SYSTEM
      Generally all newer model cars have an anti-lock brake system as normal or alternative equipment. There are many ways or method to identify if a car has an anti-lock brake system, one important way is to go through the owners manual, that way you can easily identify if the vehicle has an anti-lock brake system or not.

Monday, 13 November 2017

common causes while your car stalls

by on November 13, 2017
WHAT IS STALLING?
    Firstly, lets look at what the word stall means; Stall means to stop running or stop from making progress, typically because of an overload on the engine. A car that stalls while in motion or when you are driving is a serious and dangerous situation no matter where it happens or the cause. it could leads to accidents if it happens on the highway. As such if you are faced with similar situations where your car stalls, as am going to outline 6 common reasons why your car stalls and how to diagnose the problem and fix it asap!!! 

            6 REASONS YOUR CAR STALLS

1. FUEL PUMP
    Unfortunately, there is usually no warning when your fuel pump is dulling.  The first time you will notice any problem is after the car stalls.  When it stalls out due to a bad fuel pump, you will not be able to restart the car.
The fuel pump makes a slight buzzing noise when it is running. If you don’t hear any noise coming from the fuel tank when you try to start your car, it is likely that you have a bad fuel pump. Since you can’t start your car, your only option will be to have it towed to an autoshop.
If your car only stalls out while going up or down hills, low fuel pressure is the reason. Without enough fuel pressure, your car will not run reliably.Even if you have low fuel pressure, your car can run normally on level ground, but as soon as you head uphill, your car will probably stall without enough pressure.  Luckily, this  is one of the easiest problems to fix.
Try adding some fuel injector cleaner to your gas tank.
3.DISTRIBUTOR CAP ISSUES;
The distributor cap plays a vital role in the health of your engine. A cap is used in an to cover a car’s distributor, and its internal rotor. The distributor cap delivers voltage to the spark plugs. If the wiring is bad or the rotors become clogged, it can throw the timing off.  The spark plug will misfire if the timing is wrong.
These misfires cause cars to stall. Take a look at your distributor cap.  Make sure that it is clean and showing no signs of corrosion.
4. ELECTRICAL WIRING;
  If you’ve ruled out the reasons above, bad wiring could be to blame.
To find out if its bad wiring, check the idle speed control system. You want to ensure that the wires are connected properly. You also want to make sure that they are not starting to corrode. If you notice corrosion, it’s time to replace the wires.
5. BAD GAS;
  When there is too much moisture in the gas, it doesn’t burn properly disrupting engine performance.  If your car was running fine until the last time you filled up your gas tank, the problem is most likely caused by too much moisture in the gas.
There are two ways two fix this issue. The first is to drain the gas tank. After the gas tank is drained, fill it back up with fresh gas.
filling gas tank
6.  BAD BATTERY;
 A bad battery is one of the most common reasons that cars stall. Most people think that if a battery is dead, the car won’t start. Truth is, if your battery is going bad,your car will run but you’re at risk of stalling out. When your battery is not putting out enough power, the alternator has to work harder to keep the engine running. When the alternator overworks, it stresses the car’s engine. It is the stress on your car’s engine that actually causes your car to stall out; so it’s a domino effect.Or, could also be that the terminals are corroded and need to be cleaned or replaced. The battery is what powers your car’s electrical system, so if it’s bad then the system won’t get enough voltage, or the battery may even short out and cause intermittent problems
Check the charge on your battery. It is easy with a digital voltmeter
First, turn the car engine and headlights off. Next, pop the hood and connect the voltmeter to the terminals on the battery.
Connect the positive clamp on the voltmeter to the positive terminal on the battery. Then, connect the negative clamp to the negative terminal.
Car batteries hold 12.66 volts. Therefore, a reading of 12.66 volts on the voltmeter means that your battery if fully charged. If the voltmeter gives a reading lower than 12.45 volts, your battery needs to be recharged.
Problems with Car Alternator

Friday, 10 November 2017

STEERING WHEEL AND BRAKE VIBRATION CAUSES

by on November 10, 2017
GET RID OF STEERING WHEEL SHAKE OR BRAKE VIBRATION



    It was mid afternoon yesterday when a customer drove into my workshop with toyota rav4 2008 model, with the compain that he observed that whenever he floors the brake pedal while driving he feels the steering vibrating in his hands. This happens to be a very common issue that most cars develop with time after covering a certain kilometers and as such i want to use this medium to enlighten us on the posssible causes and how to rectify it when we are faced with such challenges.
   
WHAT IS BRAKE VIBRATION
   Brake vibration which also can be known as brake pulsation or rotor shimmying is a shaking motion that occurs when the brake system in a moving car is being deployed. This can vary from a slight shaking to a quite severe shuddering depending on the severity of the situation or condition.

WHAT CAUSES IT?
  There are many possible problems that cause steering to vibrate when brakes are deployed. it is always advised to start from the least expensive cause to the most expensive they are; dry guide pins, worn brake pads and worn rotors.
it is generally recommended if you change the rotors, you also need to change your brake pads and grease the guide pins. or if you are just replacing the brake pads, you also need to grease the guide pins. Also note that in a case where your brake pads are still in good condition, you could still  grease your guide pins. Most of this can be done with a basic set of tools. However, replacing the rotor is a little more involved.
QUICK STEPS TO CHANGE A ROTOR
-collapse the caliper
-remove the caliper
-remove the caliper bracket
-remove the rotor
-install new rotors and brakes
-grease the guide pins
-replace the caliper
-pump the brakes

Sunday, 29 October 2017

WHAT IS THE WORK OF A MASS AIR FLOW SENSOR?

by on October 29, 2017
The main purpose of the Mass Air Flow (MAF) Sensor is to measure the volume and density of air entering the engine at any given time. The computer uses this information in conjunction with input from other sensors, to calculate the correct amount of fuel to deliver to the engine. Input from this sensor is also used indirectly to help calculate desired ignition timing and transmission operating strategies. MAF sensors are mainly designed as a "hot wire" sensor or a "hot film" sensor. Both sensors function in a similiar fashion. Hot wire sensors pass current across a platinum wire and hot film sensors pass current across a foil grid. The current level is regulated to maintain the hot wire, or film, at a predetermined temperature. This temp is either a direct value, or a value that is a set number of degrees above ambient (outside) air temperature.
 
So how does this tell us how much air is getting into the engine? Well, as air passes across the mass air flow sensor, it cools the hot wire, increasing the amount of current needed to keep that wire at the specified temperature. The amount that the wire is cooled is directly proportional to the temperature, density and humidity of the air passing through the sensor and as such, the current increase needed to heat the wire allows the computer to easily calculate the volume of air entering the engine.
mass air flow sensor
Mass air flow sensors typically either send a voltage, or frequency signal to the powertrain control module (PCM). Hot wire sensors typically have an operating range of 0 - 5 volts, with idle voltage being around .5 - .8 volts and full throttle application is normally between 4 and 5 volts. Hot film sensors typically produce a frequency out put of 30 - 50 Hz with 30 Hz being idle and 150 Hz at full throttle. There are some other subtle differences between the sensors but these do not affect function or purpose.
So what types of symptoms can we get from MAF sensors, and how should we test for these faults? Well as we stated earlier, MAF sensors can produce driveability symptoms without generating a check engine light code, so some specific checks are in order. For ease of diagnosis a scan tool should be used to monitor sensor readings. In some instances it's okay to take sensor value readings by back probing the appropriate terminals at the MAF sensor. If specific MAF check engine light codes are present, then proceed with the appropriated tests. If no codes are present, or if you have lean codes you suspect are caused by a faulty mass air flow sensor, perform the following. Obtain sensor specifications from a reliable source; you can send us an e-mail from the Help Link and we can assist with most information. Hook up a scan tool with the ability to monitor sensor valves (PIDS) and pull up the mass air flow sensor. Record your MAF sensor reading at idle, and again at various RPM ranges. Compare the values against specifications. Next, start from idle and increase throttle opening while watching MAF reading. Increase should be steadily proportional to RPM change. Perform the same checks while lightly tapping on the sensor, or heating the sensor with a blow dryer. Any fluctuation, or out of specification reading indicates a mass air flow sensor, or related wiring concern. Repair and retest. I would also recommend monitoring MAF values while driving the vehicle and checking readings while the concern is present. Have an assistant drive while checking these readings. If the mass air flow reading is within specification while a concern comes and goes then it is not likely the problem. Be sure to check all air intake connections and gaskets, as well as the air filter before faulting the sensor, as these types of concerns can affect readings.

On a final note; it is not always necessary to replace a mass air flow sensor that is reading out of specification, though most dealers will tell you differently! It is possible that the sensor is just contaminated from age or use of oil saturated, aftermarket air filters. You could try exposing the sensor hot wire (once the sensor is removed from the vehicle) and cleaning it with electronic parts cleaner and low pressure air. Use appropriate cautions. Once the sensor is clean, reassemble and install and check opeation, you may be pleasantly surprised! I hope this information has been helpful. Thanks for visiting , and have a great day!

Wednesday, 25 October 2017

7 SIGNS TO KNOW YOUR FUEL PUMP IS WEAK

by on October 25, 2017


1. Engine Sputters at High Speeds

One of the best indicators of a failing fuel pump is found on the road while driving your car
 at a consistently high speed. If the vehicle suddenly sputters and then resumes regular
 performance, there may be something wrong with the fuel pump. This engine sputtering
 happens because the pump is struggling to supply a constant stream of fuel to the engine 
at the proper pressure.

2. Rising Temperature

The temperature of the car can predict a fuel pump emergency. Pay attention to your
 temperature gauge; if the heat rises and the car stalls, this may mean the fuel pump motor
 is having problems. If it continues to stall out, this is a clear sign that the fuel pump may 
be starting to deteriorate and needs to be replaced.

3. Fuel Pressure Gauge

The fuel pressure gauge shows how much fuel is getting to the engine. You can check the 
gauge while someone else is revving the car. Check the owner’s manual to see how much
 pressure should be exerted when the pump is operating properly—anything less than that
 is a signal that your fuel pump needs immediate attention.

4. Loss of Power When the Vehicle Is Under Stress

A car is put under stress when climbing a hill or hauling heavy cargo. In these situations,
 the weakening elements of the fuel pump will start to cause trouble and the pump will be
 unable to keep up with the vehicle’s fuel demands, leading to a loss of overall power.

5. Surging

Sometimes a vehicle will be moving along normally at a consistent speed and then, out of
 nowhere, it will pick up and surge forward, as if the gas pedal had been depressed. This is
 caused by irregular resistance within the fuel pump motor.

6. Decreased Gas Mileage

Always take notice of how often you’re fueling up your car. Fuel pumps have a relief valve;
 if the relief valve is failing to open, more fuel than necessary will flow into the engine 
system. If your vehicle typically gets decent gas mileage and then suddenly becomes a 
gas hog, there could be an emergency under the hood.

7. Engine Will Not Start

Drivers who ignore the warning signs above will eventually end up with an engine that
 refuses to start. When a fuel pump completely malfunctions, fuel cannot reach the
 engine upon ignition. If this happens, the engine will crank and rev but never catch. 
To diagnose a fuel pump malfunction, check for a blown fuse and/or low pressure in the
 fuel line.As a vital part of the internal combustion engine system, the fuel pump is
 something that all drivers need to keep in mind.

Sunday, 15 October 2017

DIFFERENT ENGINE SMOKE COLOURS AND THEIR MEANING

by on October 15, 2017
As a car owner you expect something to come from the tailpipe. This is an emissions outlet for your vehicle, and so vapors will exit from there. Some of the small emissions are harmless and nothing to worry about. But there are other types that can be signals of trouble from inside the car. Smoke is definitely a cause of concern and may hint of a number of problems that are happening underneath the hood of the car. You know how much you should be concerned the more you know about the emissions of smoke.
                               

                                               BLACK SMOKE



The darkest of smokes emitted from the exhaust is generally nothing much to worry about and is linked with the balance of combustion controlled by the ECU. A darker visible exhaust gas is due to an overly-rich fuel mixture, created when the air/fuel ratio descends below the optimum Stoichiometric ratio (14.7:1 in a petrol engine, 14.5:1 for diesel).The spark at ignition can only combust a certain amount of fuel in a cycle, so unburnt fuel is pushed out into the exhaust system and is combusted downstream of its intended combustion chamber.These conditions can be caused by a leaking fuel injector, a blocked fuel return pipe, a broken oxygen or airflow sensor or a fuel pressure regulator stuck closed. A dirty air filter will also prohibit nice clean air from making it through to the combustion chamber. Not only will this constrict the volume of air entering the cylinders but it will also make for less efficient combustion due to the presence of unwanted contaminants

                                  BLUE SMOKE

A blueish hue can be found from cars that have unwanted oil mixing into the air/fuel mixture. This means there’s a contaminant within the cylinders and it’s combusted along with the air and fuel.This cross-contamination is caused by engine wear to the cylinders, pistons and valves, along with failed seals like the piston rings. Engines are manufactured to high tolerances from stock, therefore any deviance in dimensions due to constant wear and tear or a slight kink in the mentioned components can allow oil (used for engine lubrication) to seep into the cylinders.A damaged valve stem, seal or guide will allow oil to make its way down from the valvetrain above the cylinder head, while a damaged piston ring will allow oil from the crankcase to squeeze its way upwards and into the cylinders.The differing pressures within the combustion chamber throughout the engine cycle will lead to oil being sucked through any leaks in the same manner as the air/fuel mixture is sucked in via the opening of the inlet valve. This can all lead to a lack of compression within the cylinders and increased pressure within the crankcase, resulting in a decrease in power.Blue smoke can be especially common in modified and turbocharged cars. By turning up the power output from an engine, much more stress is applied to each engine component, increasing wear and the possibility of oil leaks. Turbochargers themselves can fail also, allowing the oil used to lubricate the spinning turbine to spill from dodgy seals into the cylinders along with the compressed air, adding to air/fuel mixture contamination.

                                        WHITE SMOKE


It’s probably not smoke, but steam. And this can potentially be nothing to worry about, or you could be a mile or two away from an engine replacement. You may notice that from a cold start, plumes of white smoke will emanate from the exhaust tips. This is thankfully nothing to worry about and is created by vapour naturally created from combustion.When the exhaust system is still cold, the vapour will be much denser, to a point where it becomes visible. This vapour can still be seen when conditions are below ten degrees centigrade, with the temperature and air humidity changing the darkness and the visibility of the white vapour.If your car is fully warmed up, the ambient temperature is reasonable and your car is still producing steam, you could be looking at head gasket failure or even a cracked cylinder head or block from overheating.The head gasket is designed to keep the oil and coolant systems apart, along with cementing the cylinder head and combustion chambers together. A split in the gasket (mostly due to overheating or not allowing your engine to warm up gradually) will send liquids into places they really shouldn’t be. If a head gasket fails in a particular area, coolant will enter the cylinders.The engine will then try to compress and combust water, leading to potentially catastrophic engine damage and also steam pouring out of the exhaust. The size of the leak will dictate how much steam is produced but often when a head gasket goes, it really goes and you won’t be able to see out of the back window due to the steam engine that your car has suddenly become.

Saturday, 14 October 2017

TURBOCHARGER VS SUPERCHARGER

by on October 14, 2017


What is Turbocharger?


It is a forced induction system that uses exhaust gases energy to compress the air form the atmosphere and sends it to the engine cylinder. The compressed air is rich in oxygen and so the quantity of the fuel entering into the cylinder is doubled. Now the fuel burnt into the cylinder produces double power as it was producing without the turbocharger.

The turbocharger is not directly connected to the engine. It works more efficiently on high speed and spins upto 150000 rpm. Its installation is not easy and has complex design as compared with the supercharger. It experiences lag problem due discontinuous energy supply from the exhaust.


What is Supercharger?

It is also a forced induction system that compresses the air and sends it to the engine cylinder. it is generally placed on the top of the engine and directly connected to the engine crankshaft for its working. It doubles the power of engine. They are simple in design and installation. They can work on low rpm and its spin speed is upto 50,000 rpm. It more reliable and has negligible lag.


Difference between Turbocharger and Supercharger in Tabular Form

S.no
Turbocharger
Supercharger
1.
Turbocharger is a forced induction system that compresses the atmospheric gases and sends it to the engine cylinder.
Super charger is also a forced induction system. It compresses the atmospheric air and sends it to the engine cylinder.
2.
It uses exhaust gases for its energy.
It is connected to the crankshaft of the engine for its energy.
3.
It is not directly connected to the engine.
It is directly connected to the engine through belt.
4.
It has smog altering equipment which helps in lowering the carbon emission.
It doesn’t have wastegate, so the smog emits from the supercharger.
5.
It spins with a speed upto 150000 rpm.
It spins with a speed upto 50000 rpm.
6.
It is much quieter than supercharger.
It is not so quieter.
7.
It is less reliable.
It is more reliable.
8.
Maintenance is not easy.
Maintenance is easy.
9.
Turbocharger delivers their boost better at high rpm.
Supercharger can deliver their boost at lower rpm.
10.
It is more efficient.
It is less efficient.
11.
The compressed air in turbocharger has high temperature.
The compressed air in supercharger has less temperature.
12.
It requires intercooler for the compressed air to lower its temperature.
It may or may not require intercooler. But in some types, it requires intercooler.
13.
It is more complex.
It is less complex.
14.
It has lag problem due to discontinuous supply of energy.
It has negligible lag problem because of continuous supply of energy by crankshaft.
15.
The compressor is rotated by the turbine.
The compressor is rotated by the engine crankshaft through a belt.

Thursday, 12 October 2017

EFFECTS OF BAD GAS ON A CAR

by on October 12, 2017
A gasoline-powered engine needs a combination of both gasoline and air in order to start and run. Clean, high-quality gas is necessary to maximize engine operation. Bad gas can seriously disrupt normal engine operation and cause a variety of performance-related symptoms.

Engine Pinging


A major symptom of bad gas is engine pinging, or knocking, which typically occurs as the result of poor or incomplete engine combustion. Bad gasoline, which is a term normally used to refer to gasoline that has a high water content or insufficient octane, does not ignite and burn inside the engine cylinders as well as high quality gasoline. This typically causes engine pinging, especially under acceleration when improper engine combustion becomes more pronounced.

Reduced Engine Power

Bad gas does not combust and burn as well as high quality gas. As a result, bad gas typically results in poor engine performance and reduced engine power. Proper engine combustion is necessary for maximal engine power and performance. Any disruptions to normal engine combustion can reduce engine power and negatively impede normal engine performance.

Engine Hesitation

An engine will often hesitate, or stumble, during acceleration due to the effects of bad gas. Engine hesitation often occurs as the result of incomplete engine combustion, which can be caused by bad gas, in addition to fuel delivery problems and spark plug misfires. Typically, bad gas that has insufficient octane, which reduces its combustibility, is the most likely type of gas to produce engine hesitation.

Hard-Starting

A vehicle engine that is hard to start can often times be a symptom of bad gas. Ignition is dependent on a steady flow of clean, high-quality gas into the engine cylinders, where the gas is ignited by the spark plugs, which in turn causes an engine to start. Bad gas that is low in octane or high in water content can prevent or seriously retard initial engine combustion, which can cause hard-starting.