Question about 1999 Ford Explorer

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Replacing fuel injectors. the no.3&4 spark plugs get fried after a couple of months. the computer reads mixture is to lean.

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Sounds like a vacuum leak, bad O2 sensor, and not the injector. I would look for a leak near the cylinders you describe. If the injectors were bad, you would also get a P0303 and P0304 for a misfire on those cylinders.

Posted on Jul 21, 2009

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Why the spark plug keeps burning after a couple of days.Then i renew it and it will happen again.

does it start every time
check list
running hot
too much revs and load
fuel mixture too rich /lean
coil problem
burnt valve
burning oil


Jun 30, 2016 | Cars & Trucks

1 Answer

Hard to start fuel pump has been checked

Need much more information about the car, age, care it has had. Only 4 things cause hard start. Lack of Air coming into the intake, Lack of Fuel, Lack of spark, Lack of torque from the starter. Assuming the starter is good & battery, and fuel is there, i would check the spark plugs, and spark output. If it has a lot of miles check the Air Filter. The injectors could also be clogged. I always dump 2 bottles of injector cleaner in the tank every 2 months. If you have never done this i would go for 3 bottles. Again the spark cannot be weak, fuel pressure cannot be low, or have restrictions like dirty a fuel filter, or dirty fuel injectors or even bad Gas. And last a computer problem providing incorrect timing to the Injectors or Spark Plugs.

Apr 23, 2016 | Nissan Pathfinder Cars & Trucks

1 Answer

Misfire on cylinder 4

How the computer determines a misfire is through a lagging effect in the crankshaft turning-when one cylinder is not producing power, the crankshaft doesn't turn as fast, and the computer senses it through the crankshaft sensor.
Misfires are usually a fuel problem, spark problem, or a low compression problem. Compare the spark at #4 with the other cylinders-all should have a blue, snapping spark. If good spark, check the spark plug -it might be defective. Compare the spark plug in #4 with the others. If it has a black sooty appearance, it is running rich-injector may be leaking. If the lower insulator on #4 is whiter than the other plugs, it is running lean, and the injector may be partially clogged, or not pulsing well.
If gas and spark is good, do an engine compression test. If #4 has low compression, it could be a valve problem, or worn piston rings, or a head gasket failure.

Mar 29, 2014 | Nissan Cars & Trucks

1 Answer

System lean bank 1 p0172 fuel

PO 171 Bank 1 too lean
PO 174 Bank 2 too lean
Why ?
The front O2 Sensors need to be replaced at
100,000 miles or sooner, if they have actually failed
They are reading too lean because the system is too
rich & the computer is driving the fuel trim or injector
pulse lean, thus the codes or failed sensors, yes both
Have to check fuel trim with a scan tool
Have to check fuel pressure
Have to check there are no leaking injectors
Have to check for Vacuum Leaks from the intake
all the way to the exhaust converter
Your working a rich condition keeping in mind the system
is driven lean
You look at fuel trim short & long,sort of a past history
of events
May want to look at converter temps also
The converters won't last long if you have or has
a rich condition from fuel or cylinder misfires
Now the spark plugs can't be over 3 years old
& no mifires,get that out of the way before working
the O2 issues

Jul 27, 2013 | 2005 Mitsubishi Endeavor

2 Answers

96 gmc 5.7..too much fuel to the injectors, fowling plugs and runs rough//showing codes of multible miss fires and 02 sensoer whitch has been replaced

Could be a number of issues. Fuel pressure or regulator issue, but...
If you have a coolant sensor problem, as in reading wrong, and it tells your computer it is colder than it actually is,,,you will get more fuel delivery.

Aug 31, 2011 | 1996 GMC Sierra

2 Answers

Hello , I have a 2000 dodge Durango v6 with a po305 code , I replaced basic plugs wires cap & rotor . It smells rich with fuel and has a little mis at idle . Any ideas as to why it would be running...

P0305 code is a cylinder #5 missfire. The codes last digit is the effected cylinder, i.e. P0305 is cylinder #5 and a P0302 is cylinder #2 and so on. A P0300 is a multi-cylinder missfire.
Thoery 1: Ignition system! If the cylinder is being injected with fuel and not getting spark, the un-burned fuel would simply be pumped out the exhaust system and can be the source of the fuel smell. Check the ignition system and the firing order. I know you said you already did this, but I have to include this for other people in the future who might be using this to help them with a simillar problem.
Theory 2: Bad injector! If #5 cylinder injector is stuck at full fuel (leaking badly due to an internal mechanical failure) it will be pumping way too much fuel into the cylinder for the cylinder to burn. The outcome is the same as before, it just pumps the raw fuel out the exhaust system. Just as before, compare 2 cylinders by inspecting the spark plugs of #3 and #5. If an injector is stuck, that cylinder spark plug will be soaked with fuel. Injectors cannot be repaired, just replaced.
Theory 3: Low compression! If #5 cylinder is low on compression it will not fire the fuel as it is injected. A simple compression test is needed to tell if there is a mechanical failure internal to the engine causing low compression.
Theory 4: Bad intake plenum gasket! The intake manifold has a steel plate bolted onto the bottom of it with a gasket called a plenum. This plate is inside the lifter valley. If this gasket fails it will cause a vaccume leak into the intake manifold that will create a lean mixture condition for the cylinder that is nearest the failed spot. This lean mixture does not light or burn effectivly and can cause an unburned mixture to enter exhaust manifold causing the same sympoms as above.
Obviously this problem needs further diagnostics to pin-point the source of the failure. These are simply starting points and there can be many other things that can cause this type of problem, but these are the most likely. Hope this can be of some help, have more questions? Just ask!

Mar 26, 2011 | Dodge Durango Cars & Trucks

3 Answers


P0301 - Cylinder 1 Misfire Detected.

- Improper spark plug at cylinder #1
- Insufficient compression at cylinder #1
- Incorrect fuel pressure
- The injector circuit is open or shorted at cylinder #1
- Fuel injector #1 may be faulty
- Intake air leak

- Perform Injector Service
- Replaced Spark Plug #1
- Replaced Injector #1
- Replaced Ignition Coil #1

P0303 - Cylinder 3 Misfire Detected.
Follow info from P0301.

P0316 - Misfire Occurred In The First 1,000 Engine Revolutions.

- Damaged CKP sensor.
- Ignition System.
- Fuel Injectors
- Running out of fuel
- Fuel Quality
- Base engine
- Damaged Powertrain Control Module

Usually the P0316 is combine with a P03XX codes. The P03XX code indicates in which cylinder the misfire occurred.

Jan 17, 2011 | 2002 Mercury Sable

1 Answer

2002 Kia Sedona 3.5L V6. Computer reads lean fuel mixture. Already replaced fuel filter and pump. This mixture problem has existed for over 3 years and has baffled more than 6 ASE mechanics. What are...

Fuel Filter and Pump-won't cause a lean condition,unless you don't have sufficient volume.
Air leaking in around injector O-Rings
Any kind of air leak,including intake manifold,loose O2 Sensors,Etc,Etc

6 ASE people should be able to figure it out!!!

Look at all Data on an Oscilloscope.
The fact that the computer reads lean--IS IT a lean condition.
Check tailpipe emissions to confirm,lean

Apr 29, 2010 | 2002 Kia Sedona

1 Answer

Check engine light on. 4 cylinder. Light flashes on acceleration. Sometimes idles rough. Computer scan reads random misfire and #2 & #3 misfiring. Added fuel injector cleaner but no help yet. Cleared...

There are three kinds of gasoline engine misfire scenarios, first there is the "under load" misfire and there is the "at engine idle" misfire, and finally there is misfire continuously. All engine misfires exist because one of three things has occurred. First, a cylinder has lost compression, a cylinder needs a certain amount of compression to operate correctly. Second, the ignition system has failed or is failing intermittently, spark is needed at the time of compression to ignite the fuel air mixture. Third, the fuel air mixture is incorrect, proper mixture is needed for the ignition system to ignite fuel properly. If any of these conditions occur in the engine, the engine will misfire.
1. Low or no compression can be caused by

a. burned or leaking intake or exhaust valves
b. worn or broken piston or piston rings
c. worn out camshaft
d. wrong weight motor oil was installed holding the cam followers from adjusting
e. broken valve spring
f. failed head gasket.
2. Ignition system has failed or is failing
a. spark plug has fouled or is worn out
b. ignition coil
has failed
c. spark plug wires have shorted
e. engine control module coil driver has failed
3. Fuel/Air Mixture is incorrect
a. vacuum leak at the intake manifold
b. fuel injector has failed
c. EGR valve is stuck open
d. mass air flow sensor has failed
e. oxygen sensor has failed
f. air intake boot is cracked

common problems:
1. fuel injector has failed or is failing
2. spark plug wire has shorted
3. spark plug is worn out or is cracked
4. ignition coil has failed is failing

Testing a coil on the car is pretty easy. No special tools are required. Just remember to be careful, the amount of electricity generated by your ignition system can be dangerous. If your coil is already off the car, or if you would like a more specific data-driven test, you can bench test your coil. To set up the test, remove one spark plug wire from its plug, then remove the spark plug using a spark plug socket. Next put the spark plug back into the spark plug wire. Be careful not to let anything drop into the empty spark plug hole -- very bad.

Dec 07, 2008 | 1999 Toyota Camry

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