Question about 1999 Chevrolet Tahoe

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I got a 99 tahoe 5.7 vortec with multiple misfires under load/accelerating. So far Ive replaced; plugs, wires, cap n rotor, coil, egr valve, fuel filter, o2 sensors. Tested; vacuum, fuel pressure, OBD 2 scan. All in which came back ok/no codes. It runs great with the new wires and stuff, but still chugs and sputters when I accelerate or under load! WTF should I do next?...

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  • Don Vanemon
    Don Vanemon Jan 31, 2014

    i had the same problem with my 1998 5.7 after changing everything you did and more. it was the injector spider

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  • Master
  • 1,857 Answers

This is one of those situations that a professional diag would of saved you alot of money. Its possible you just got bad gas and your injectors are partially clogged. An 02 sensor would not give multible misfires. EGR would only misfire at idle if stuck partially open since its suppose to be open cruising. Fuel filter would give you a starvation issue but if the misfires happens at idle then the filter most likley is ok.
Data from a professional data scanner will store the conditions when the misfire occurs. Also for a chevy each cylinder will have a misfire counter and one can see the misfire happening as it happens. If its idling and misfiring and gets better as you rev it up most likely you have clogged injectors or a intake vacuum leak. You can test for a intake leak by spraying the intake area with water(idle will faulter if it draws water in), or use brake cleaner (idle will raise when fluid gets drawn in).

If no leaks are found I would do an injection service or at least add two bottles of techron to a full tank, drve till half a tank then top off again.

Also if the catalytic converter is clogged the backpressure could cause all sorts of misfire issues. Removing the two upfront 02 sensors and driving will indicate the exhaust is clogged or not. We put a pressure sensor in place of the 02 sensor. If the pressure is above 5psi this would indicate some blockage. It should be below 3psi at 2000 rpm. Also if you have K/N filter the oil from it will coat the maf sensor wires in time,, (always). You can remove the sensor and spray the wires with brake cleaner to clean. DO NOT touch them. They can be brittle. Look at the wires for color. They should be shiny silver. If its coated the PCM will not see the air volume or accurately see the air temperature. Without this information the PCM will not add enough fuel which will create a misfire.

Posted on Jul 07, 2010

  • Susan Price Jul 07, 2010

    By the way, how did you check the fuel pressure. Did you do a volume test and also check for air being drawn. Chevys have a major issue with fuel pumps failing or leaking internally. Do a search on chevy fuel pump failures and repeat fuel pump failures to understand my point. You will need this info if you plan on replacing the fuel pump. Its possible the connector at the fuel pump is overheating and melting due to poor connections.

  • tanyaprescot May 03, 2011

    My truck was doing the same thing and I did the mass airflow sensor and it is running fine, same truck 99 tahoe 2 dr, 4wd

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I had the same problem with my 1998 5.7 and changed everything possible. it ended up being the injector spider...good luck part alone was $600.00 but its fixed

Posted on Jan 31, 2014

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Just had the same problem on my 1998 5.7 vortec first it started with just the #6 misfire then multiple misfires. turns out it was a bad fuel injectors. Since i was towing my boat i ignored it for a couple hundred mile till i got to my destination. BAD MOVE!!!! because the injector wasnt working the cylinder was lean and burned my exhaust valve and froze it in the open position. SO fix it right away. not only did i have to replace the fuel injectors i had to replace the head....

Posted on Aug 11, 2010

  • crlos83 Oct 17, 2010

    I had the same problem with the service engine light coming on under heavy towing conditions or going up hills. After about 8 hours of diagnostics, I found out that one of the catalytic converters was clogged. After I cleaned out the cat conv. with sea foam I realized that the pressure had decreased and thus decreasing the misfiring. However, the problem was only a temporary fix as I am now having the problem again (after about 6-8 months) and am going to need to replace one of the cat conv.

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Posted on Jan 02, 2017

  • 102 Answers

SOURCE: Ive got a 99 tahoe, 5.7 vortec, with 165k. Its

Most of the time when you run a fuel system cleaner in a engine that has not had a cleaning the sludge will clog the fuel filter. I would check the fuel filter before anything and if that is good, I recommend running a complete test on the vacuum lines sometimes if there is a leak in a vacumn line it will mess with the timing advance and cause the vehicle to behave different at certain RPM ranges

Posted on May 18, 2010

juncro
  • 467 Answers

SOURCE: 1998 astro sputtering when taking off and while at driving speed

loose vacuum line, check for same, also check the map sensor and the measure the fuel pressure, make sure its at spec

Posted on Jul 29, 2009

  • 1 Answer

SOURCE: van sputters whenever you go to take off from a

hi there, i had the same problem with my 98 astro van, and took it to the shop, the computer pumped out a mass airflow sensor, they replaced it at considerable cost lol, but the van now runs good

Posted on Jul 03, 2010

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1 Answer

What is code p0300?


P0300 - Random, Multiple Cylinder Misfire Detected Fault Code Definition
  • Random, Multiple Misfire Detected
Symptoms
  • Check Engine Light flashing
  • Rough running, hesitation, and/or jerking when accelerating
  • In some cases, there may be performance problems, such as dying at stop signs or rough idling, hesitation, misfires or lack of power (especially during acceleration), and a decrease in fuel economy
Common Problems That Trigger theP0300
  • Worn out spark plugs, ignition wires, coil(s), distributor cap and rotor (when applicable)
  • Incorrect ignition timing
  • Vacuum leak(s)
  • Low or weak fuel pressure
  • Improperly functioning EGR system
  • Defective Mass Air Flow Sensor
  • Defective Crankshaft and/or Camshaft Sensor
  • Defective Throttle Position Sensor
  • Mechanical engine problems (i.e.-low compression, leaking head gasket(s), or valve problems

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Egr valve for 1997 cheve Blazer code is 0300 misfireing what could be the trouble


usually this code is followed by another number 1-4 or 1-6 or 1-8 depending on how many cylinders your vehicle has ,, what the code you got is a basic P0300 Random/Multiple Cylinder Misfire Detected 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
  • 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 ope

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2004 Acura MDX 3.5 130,000 miles multiple missfire how do i fix ?


Hi, multiple cylinder misfire, is when the engine cylinders do not fire in the correct order, and do not do it constantly. There is no particular pattern to it. My experience with this condition is that it is usually caused by a faulty ignition coil that is beginning to burn out. It could also be bad wires pluds rotor or cap

Causes Include.
  • 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 Solution:
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. 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 11, 2011 | 2004 Acura MDX

2 Answers

P0305 code, new plugs, wires, cap, rotor, coil, fuel filter and still getting p0305 code any good ideas?


means misfire in #5 cylinder. found this for you. hope this helps
Common Problems That Trigger the P0305
  • Worn out spark plugs, ignition wires, coil(s), distributor cap and rotor (when applicable)
  • Incorrect ignition timing
  • Vacuum leak(s)
  • Low or weak fuel pressure
  • Improperly functioning EGR system
  • Defective Mass Air Flow Sensor
  • Defective Crankshaft and/or Camshaft Sensor
  • Defective Throttle Position Sensor
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Common Misdiagnoses
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Jan 05, 2011 | 1999 Chevrolet Suburban

1 Answer

Multiple missfire code po300


P0300 Diagnostic Code - 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.


Test it and keep us updated.

Jan 04, 2011 | 1999 Chevrolet Tahoe

1 Answer

I ran a scanner on my 2002 pontiac grand prix 3100 V6 and it reads out as multiple misfire i already changed the spark plugs,what could the problem be?


A code “multiple misfire” 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 (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.

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My 1996 Astro does the same thing... It has new fuel pump, fuel filter, plugs, wires, cap, rotor, maf sensor, ignition coil, alt., battery, cat converter, im stumped...

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