Hi, I have a 2002 Isuzu Elf 4Hg1 Engine. It has been misfiring, they changed two injectors that they said was the cause of the problem. The problem has somewhat improved, however when accelerating in the lower gears it feels as if its been pulling back until it reaches a higher RPM then it clears up. There is also an excess of black smoke when accelerating. Thank you

SOURCE: misfiring on right side at low rpm.

could be a catalytic converter or o2 sensor. really would need to hook it up to a proper scan tool to view live data while running.

SOURCE: Ford Expedition knocks at low RPM and misfires

SCRAP IT

honeymokey

• 3113 Answers
• Posted on Jul 24, 2009

SOURCE: 2004 Isuzu Rodeo 3.5ltr 4X4 hesitation/misfire acceleration

The upper intake gaskets may be leaking. They are made of plastic and metal and will leak air. Do not remove the cover on very top of manifold when changing.

SOURCE: my grang cherokee2002 us spec, while driving trnz

When revving the engine while the transmission is in park, you are over revving and the rpm limiter is causing the engine to return to 5000 rpm. Your engine should perform better at high rpms. A good tune up with new spark plugs and wires should help, but you won't get much more than 5000 rpm before the rev limiter kicks in and drops the engine back to 4.5 or 5. 6000 rpm is the maximum revs for the high performance V8 engine. If you have the v6 engine, your maximum rpm should be around 5200. If the engine is getting noisy at 5000 rpm, you are risking serious engine damage, or it could already be damaged, by repeatedly revving that high. Check your owners manual and see what the maximum rpm is for your engine.

ZJ Limited

• 17989 Answers
• Posted on May 26, 2011

SOURCE: isuzu 2004 rodeo 3.5: Engine light,

Multiple Misfiring basically this means that the the car's computer has detected that not all of the engine's cylinders are firing properly. This is P0300 diagnostic code and indicates a random or multiple misfire; when you using one scanner reader, 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.

Check it and keep us updated.