Question about 2002 Jeep Grand Cherokee

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Cylinder number one stops firing, and black smoke comes out of the exhaust. I replaced the coil pack and spark plugs. when i unplug battery and reset the faults, it drives fine for a couple days. what could be the problem. please help. thank you

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Honestly it sounds like you have a bad computer. there is a constant 12 volts going to each fuel injector and the computer momentarily grounds each fuel injector to activate, the black smoke is from too much gasoline and the missfire is probably from the injector either hanging open or being held open electricaly. next time it starts to missfire on number 1 cylinder try taking a stethiscope or long screw driver and put it on #1 fuel injector with the engine running and see if you hear a clicking sound. If not try unplugging the #1 Fuel injector. this won't fix the missfire but you can see if the black smoke clears up. if the smoke doesn't clear up with the injector unplugged and you are sure its # 1 cylinder thats missing, replace #1 fuel injector.

Posted on Jul 10, 2010

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05 Ford Escape, coils #3 & #4 not firing. We've replaced the battery, spark plugs, alternator, coil packs, & pcm. Had pcm reflashed. Garage said it had to be coil packs, but just replaced coil packs 3


Check engine light on ? Code's ? What engine ? 2.3 l 4cylinder or 3.ol v-6 This vehicle has coil on plug ignition system , not coil packs ! a coil per cylinder . If new coils an still has no spark , has no B+ voltage to the coil or the PCM isn't controlling them . Without testing i'd only be guessing as to the problem .If the repair shop you had it to can only say it had to be the coils , I'd find another shop to take it to !
Autolite Coil on Plug Ignition troubleshooting

Jun 22, 2017 | Cars & Trucks

1 Answer

My 1999 firebird has been on a computer and a firing problem for number 5 cylinder came up, changed plugs and plug wires and its still doing it what else could cause this problem


Misfire #5 may mean that one or more of the following has happened:
Faulty spark plug or wire
Faulty coil (pack)
Faulty oxygen sensor(s)
Faulty fuel injector
Burned exhaust valve
Faulty catalytic converter(s)
Running out of fuel
Poor compression
Defective computer

If there are no symptoms, the simplest thing to do is to reset the code and see if it comes back. If there are symptoms such as the engine is stumbling or hesitating, check all wiring and connectors that lead to the cylinders (i.e. spark plugs). Depending on how long the ignition components have been in the car, it may be a good idea to replace them as part of your regular maintenance schedule. I would suggest spark plugs, spark plug wires, distributor cap, and rotor (if applicable). Otherwise, check the coils (a.k.a. coil packs). In some cases, the catalytic converter has gone bad. If you smell rotten eggs in the exhaust, your cat converter needs to be replaced. I've also heard in other cases the problems were faulty fuel injectors.

Hope this helps.

Oct 06, 2011 | 1999 Pontiac Firebird

2 Answers

2003 mustang cylinder 2 misfire. I changed the spark plugs and wires. Its still have code p0302. What should I do next?


A code P0302 may mean that one or more of the following has happened:
Faulty spark plug or wire
Faulty coil (pack)
Faulty oxygen sensor(s)
Faulty fuel injector
Burned exhaust valve
Faulty catalytic converter(s)
Running out of fuel
Poor compression
Defective computer

Possible Solutions:
* If there are no symptoms, the simplest thing to do is to reset the code and see if it comes back.
* If there are symptoms such as the engine is stumbling or hesitating, check all wiring and connectors that lead to the cylinders (i.e. spark plugs). Depending on how long the ignition components have been in the car, it may be a good idea to replace them as part of your regular maintenance schedule. I would suggest spark plugs, spark plug wires, distributor cap, and rotor (if applicable). Otherwise, check the coils (a.k.a. coil packs). In some cases, the catalytic converter has gone bad. If you smell rotten eggs in the exhaust, your cat converter needs to be replaced. I've also heard in other cases the problems were faulty fuel injectors.

Keep us updated.

Sep 06, 2011 | 2003 Ford Mustang

1 Answer

When I have my Air Conditioner on my check engine light comes on. The engine studers. This doesn't happen right away. The OBD codes I get are P0300, P0303, P0304, P0305.


Basically this means that the the car's computer has detected that not all of the engine's cylinders are firing properly.
A P0300 diagnostic code indicates a random or multiple misfire. If the last digit is a number other than zero, it corresponds to the cylinder number that is misfiring. A P0302 code, for example, would tell you cylinder number two is misfiring.


A code P0300+ may mean that one or more of the following has happened:
  • Faulty spark plugs or wires
  • Faulty coil (pack)
  • Faulty oxygen sensor(s)
  • Faulty fuel injector(s)
  • Burned exhaust valve
  • Faulty catalytic converter(s)
  • Stuck/blocked EGR valve / passages
  • Faulty camshaft position sensor
  • Defective computer
  • Running out of fuel
  • Poor compression

If there are no symptoms, the simplest thing to do is to reset the code and see if it comes back.

If there are symptoms such as the engine is stumbling or hesitating, check all wiring and connectors that lead to the cylinders (i.e. spark plugs). Depending on how long the ignition components have been in the car, it may be a good idea to replace them as part of your regular maintenance schedule. I would suggest spark plugs, spark plug wires, distributor cap, and rotor (if applicable). Otherwise, check the coils (a.k.a. coil packs). In some cases, the catalytic converter has gone bad. If you smell rotten eggs in the exhaust, your cat converter needs to be replaced. I've also heard in other cases the problems were faulty fuel injectors.

Jun 02, 2011 | BMW 328 Cars & Trucks

2 Answers

Error code P0300


A P0300 diagnostic code indicates a random or multiple misfire
If there are no symptoms, the simplest thing to do is to reset the code and see if it comes back
Symptoms may include:
  • the engine may be harder to start
  • the engine may stumble / stumble, and/or hesitate
  • other symptoms may also be present

A code P0300 may mean that one or more of the following has happened:

  • Faulty spark plugs or wires
  • Faulty coil (pack)
  • Faulty oxygen sensor(s)
  • Faulty fuel injector(s)
  • Burned exhaust valve
  • Faulty catalytic converter(s)
  • Stuck/blocked EGR valve / passages
  • Faulty camshaft position sensor
  • Defective computer

If there are symptoms such as the engine is stumbling or hesitating, check all wiring and connectors that lead to the cylinders ( spark plugs). Depending on how long the ignition components have been in the car, it may be a good idea to replace them as part of your regular maintenance schedule. I would suggest spark plugs, spark plug wires, distributor cap, and rotor (if applicable). Otherwise, check the coils (coil packs). In some cases, the catalytic converter has gone bad. If you smell rotten eggs in the exhaust, your cat converter needs to be replaced. I've also heard in other cases the problems were faulty fuel injectors.

Random misfires that jump around from one cylinder to another (read: P030x codes) also will set a P0300 code. The underlying cause is often a lean fuel condition, which may be due to a vacuum leak in the intake manifold or unmetered air getting past the airflow sensor, or an EGR valve that is stuck open

Jan 23, 2011 | 2004 Kia Amanti

1 Answer

2002 jeep liberty. Codes P0300,301, 302


P0300 - Random/Multiple Cylinder Misfire Detected
Basically this means that the the car's computer has detected that not all of the engine's cylinders are firing properly.

A P0300 diagnostic code indicates a random or multiple misfire. If the last digit is a number other than zero, it corresponds to the cylinder number that is misfiring. A P0302 code, for example, would tell you cylinder number two is misfiring. Unfortunately, a P0300 doesn't tell you specifically which cylinder(s) is/are mis-firing, nor why.

Symptoms may include:
* the engine may be harder to start
* the engine may stumble / stumble, and/or hesitate
* other symptoms may also be present

Causes: A code P0300 may mean that one or more of the following has happened:
* Faulty spark plugs or wires
* Faulty coil (pack)
* Faulty oxygen sensor(s)
* Faulty fuel injector(s)
* Burned exhaust valve
* Faulty catalytic converter(s)
* Stuck/blocked EGR valve / passages
* Faulty camshaft position sensor
* Defective computer

Possible Solutions
- If there are no symptoms, the simplest thing to do is to reset the code and see if it comes back.
- If there are symptoms such as the engine is stumbling or hesitating, check all wiring and connectors that lead to the cylinders (i.e. spark plugs). Depending on how long the ignition components have been in the car, it may be a good idea to replace them as part of your regular maintenance schedule. I would suggest spark plugs, spark plug wires, distributor cap, and rotor (if applicable). Otherwise, check the coils (a.k.a. coil packs). In some cases, the catalytic converter has gone bad. If you smell rotten eggs in the exhaust, your cat converter needs to be replaced. I've also heard in other cases the problems were faulty fuel injectors.

Random misfires that jump around from one cylinder to another (read: P030x codes) also will set a P0300 code. The underlying cause is often a lean fuel condition, which may be due to a vacuum leak in the intake manifold or unmetered air getting past the airflow sensor, or an EGR valve that is stuck open.


P0301 Code - Cylinder #1 Misfire
P0302 Code - Cylinder #2 Misfire

A P0301 or P0302 code means that the the car's computer has detected that one of the engine's cylinders is not firing properly. In this case it's cylinder #1 or #2

Symptoms may include:
* the engine may be harder to start
* the engine may stumble / stumble, and/or hesitate
* other symptoms may also be present

Causes: A code P0301 or P0302 may mean that one or more of the following has happened:
* Faulty spark plug or wire
* Faulty coil (pack)
* Faulty oxygen sensor(s)
* Faulty fuel injector
* Burned exhaust valve
* Faulty catalytic converter(s)
* Running out of fuel
* Poor compression
* Defective computer

Possible Solutions:
- If there are no symptoms, the simplest thing to do is to reset the code and see if it comes back.
- If there are symptoms such as the engine is stumbling or hesitating, check all wiring and connectors that lead to the cylinders (i.e. spark plugs). Depending on how long the ignition components have been in the car, it may be a good idea to replace them as part of your regular maintenance schedule. I would suggest spark plugs, spark plug wires, distributor cap, and rotor (if applicable). Otherwise, check the coils (a.k.a. coil packs). In some cases, the catalytic converter has gone bad. If you smell rotten eggs in the exhaust, your cat converter needs to be replaced. I've also heard in other cases the problems were faulty fuel injectors.


Hope ths helps. Keep us updated and remember to rate this answer.

Jan 03, 2011 | 2002 Jeep Liberty

1 Answer

4.7l V-8---error code P0308 is being displayed---about a year ago, I replaced the plugs and all 8 coil packs---thanks


Hi. This P0308 code means that the the PCM has detected that one of the engine's cylinders are not firing properly. In this case it will be cylinder Number 8.

A code P0308 may indicate that one or more of the following has occurred:

1 Faulty spark plug or wire
2 Faulty coil (pack)
3 Faulty oxygen sensor(s)
4 Faulty fuel injector
5 Burned exhaust valve
6 Faulty catalytic converter(s)
7 Running out of fuel
8 Poor compression
9 Defective computer

If there are no symptoms, the first thing to do is to reset the code, with a code reader, and see if it comes back. If there are symptoms such as the engine is stumbling or hesitating, check all wiring and connectors that lead to the affected cylinder and plug/coil assembly. Depending on how long the ignition components have been in the car, it may be a good idea to replace them as part of your regular maintenance schedule. I would suggest spark plugs, spark plug wires, distributor cap, and rotor (if applicable). Otherwise, check the coils (a.k.a. coil packs-COP-). In some cases, the catalytic converter has collapsed. If you smell rotten eggs in the exhaust, your converter may need to be replaced. I've also been told several times that the problem in this case could be a faulty injector at that cylinder 8.

Sep 04, 2010 | 2004 Dodge Ram 1500

1 Answer

Timing the cams and crank with a belt


  1. Note: Electronic Ignition engine timing is entirely controlled by the PCM. Electronic Ignition engine timing is NOT adjustable. Do not attempt to check base timing. You will receive false readings.

The CKP sensor is used to indicate crankshaft position and speed by sensing a missing tooth on a pulse wheel mounted to the crankshaft. The CMP sensor is used by the COP Integrated EI System to identify top dead center of compression of cylinder 1 to synchronize the firing of the individual coils.
  1. The PCM uses the CKP signal to calculate a spark target and then fires the coil pack(s) to that target shown in Figure 51. The PCM uses the CMP sensor not shown in Figure 51 on COP Integrated EI Systems to identify top dead center of compression of cylinder 1 to synchronize the firing of the individual coils.
  1. The coils and coil packs receive their signal from the PCM to fire at a calculated spark target. Each coil within the pack fires two spark plugs at the same time. The plugs are paired so that as one fires during the compression stroke the other fires during the exhaust stroke. The next time the coil is fired the situation is reversed. The COP system fires only one spark plug per coil and only on the compression stroke.

    The PCM acts as an electronic switch to ground in the coil primary circuit. When the switch is closed, battery positive voltage (B+) applied to the coil primary circuit builds a magnetic field around the primary coil. When the switch opens, the power is interrupted and the primary field collapses inducing the high voltage in the secondary coil windings and the spark plug is fired. A kickback voltage spike occurs when the primary field collapses. The PCM uses this voltage spike to generate an Ignition Diagnostic Monitor (IDM) signal. IDM communicates information by pulsewidth modulation in the PCM.
  1. The PCM processes the CKP signal and uses it to drive the tachometer as the Clean Tach Out (CTO) signal.

2.5L V6

The ignition system consists of an ignition coil, spark plug wires and spark plugs.
The crankshaft position sensor signal is the basis for ignition timing calculations. The alternating voltage signal from the crankshaft position sensor is digitized by a pulse former within the powertrain control module. This digitized signal is then used to position the closing time of the primary circuit of the ignition coil.
Ignition timing is determined by the powertrain control module in response to engine operating conditions based on stored data tables or maps. Once ignition timing has been determined, the powertrain control module interrupts the current to the primary circuit of the ignition coil thus triggering the ignition spark which is supplied to the cylinders through the spark plug wires and spark plugs.
The ignition coils are triggered by the powertrain control module in pairs (cylinders 1 and 5, cylinders 4 and 3 and cylinders 2 and 6) sending one ignition spark to the firing cylinder and one ignition spark to the corresponding cylinder on the exhaust stroke. This ensures that any unburnt fuel residues remaining in the cylinder on the exhaust stroke are re - ignited to provide cleaner exhaust emissions.
---------------------------------------------------------------
2.0L 4 cynder

The ignition system consists of an ignition coil, spark plug wires and spark plugs.
The crankshaft position sensor signal is the basis for ignition timing calculations. The alternating voltage signal from the crankshaft position sensor is digitized by the powertrain control module. This digitized signal is then used to position the closing time of the primary circuit of the ignition coil.
Ignition angle is determined by the powertrain control module in response to engine operating conditions. Once ignition angle has been determined, the powertrain control module interrupts the current to the primary circuit of the ignition coil thus triggering the ignition spark which is supplied to the cylinders through the spark plug wires and spark plugs.
The ignition coils are triggered by the powertrain control module in pairs (cylinders 1 and 4 and cylinders 3 and 2) sending one ignition spark to the firing cylinder and one ignition spark to the corresponding cylinder on the exhaust stroke. This make sures that any unburnt fuel residues remaining in the cylinder on the exhaust stroke are re - ignited to provide cleaner exhaust emissions.
------------------------------------------------------------------------------------
Integrated Electronic Ignition System The Integrated Electronic Ignition (EI) System consists of a crankshaft position (CKP) sensor, coil pack(s), connecting wiring, and PCM. The Coil On Plug (COP) Integrated EI System uses a separate coil for each spark plug and each coil is mounted directly onto the plug. The COP Integrated EI System eliminates the need for spark plug wires but does require input from the camshaft position (CMP) sensor.
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Apr 05, 2009 | 1998 Ford Contour

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