Question about 2000 Toyota 4Runner

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Running a little rough at low rpm, hooked up to diagnostic test, pulled out a p306 code. Changed spark plugs, wires, ignition coils, and both O2 sensors. Now it wants to start, but won't. It sounds like it is either not getting enough air, or fuel to ignite?

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As you mentioned that spark plugs are replaced,so with new spark plugs,this can be fuel related problem.Get the fuel pressure tested.If the pressure checked out low then can be faulty fuel pump and clogged fuel filter.But as you mentioned,that before replacing the parts,it was running rough,as per that clean the MAF sensor and see.The MAF sensor is located on top of the air box, the black plastic box on the right side of the engine. It is held in place by two little screws and has a wire harness clipped to it.Remove this sensor and clean it,then reconnect it and checked. also try spraying some starter fluid in the intake and see.If it starts,then its fuel pressure regulator problem.The fuel is actually not reaching the fuel rail,due to this engine turns over but will not start running,because the fuel is not reaching. check the FP regulator by pulling off the vacuum hose that goes to it---if fuel dribbles out of there, then the FP regulator is no good. NOTE:---Do not spray too much starter fluid and if your car starts and runs properly with starter,fluid,dont use starter fluid again n again to start your car.Its just for testing,not for regular driving.Its not good for car.Too much starter fluid can "wash" cylinder walls of their lubrication. Never use it while the engine is actually running.----------------check out this possibilities.This should help.Thanks.helpmech

Posted on Jan 01, 2011


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2005 buick lacrosse 3.8 changed spark plugs coils N wires still shakes and sputters rough idle

The basics for vehicle with rough idle, check for a leak of some kind, fuel--egr--vacuum leak. How long since an over-all tune-up? You can check the idle air system? Any applicable trouble codes? To check codes yourself, at the least, you need an obd2 code reader.
If spark issue, sometimes you can use a digital multimeter to do some testing, low tech, non--invasive. With digital multimeter on low voltage setting, engine idling, touch spark plug wires, one at a time, do not penetrate insulation, don't take spark plug wire loose, it's an inductive reading. The point is if you get a reading bouncing off zero, that is where you start testing. I know you changed the coil/s, but sometimes, you need to check ignition module. I'm not saying that module is faulty, I don't know.

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My 2003 pontiac aztek shuts off when its in idle

Could have a vacuum leak , a problem with the IAC - idle air control motor !
Rough, Unstable, or Incorrect Idle and Stalling
DEFINITION: Engine runs unevenly at idle. If severe, the engine or vehicle may shake. Engine idle speed may vary in RPM. Either condition may be severe enough to stall the engine.
Refer to Diagnostic System Check - Engine Controls .

Refer to Intermittent Conditions before starting.

Search for bulletins.

Observe the owners driving habits.

Fuel System
Test the fuel system circuits for proper operation. Refer to Fuel Pump Electrical Circuit Diagnosis .

Test for low fuel pressure. Refer to Fuel System Diagnosis .

Test for faulty fuel injectors. Refer to Fuel Injector Balance Test with Special Tool , Fuel Injector Balance Test with Tech 2 , Fuel Injector Solenoid Coil Test test procedures.

Inspect for fuel contamination. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .

Inspect for fuel in the pressure regulator vacuum hose.

Ensure each injector harness is connected to the correct injector/cylinder.

Inspect for any items which may cause an engine to run rich, long term fuel trim is significantly in the negative range. Refer to Diagnostic Aids for DTC P0172 .

Inspect for any items which may cause an engine to run lean, long term fuel trim is significantly in the positive range. Refer to Diagnostic Aids for DTC P0171 .

Test for conditions which cause an incorrect idle speed.

Throttle body tampering, excessive deposits, or damage--Refer to Fuel System Description .

Restricted air intake system

Large vacuum leak

Inspect the air intake ducts for being collapsed, damaged areas, looseness, improper installation, or leaking especially between the MAF sensor and the throttle body.

Inspect crankcase ventilation valve for proper operation.

Inspect the throttle position (TP) sensor and related wiring. Refer to DTC P0123 .

Monitor the 24X crank sensor and the CMP sensor signal present parameters on the scan tool. If both are not responding, test the sensor feed circuit. Both sensors use a separate feed circuit but are internally connected to power. Test all CKP sensor A and CMP sensor circuits for intermittents. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Monitor the 3X parameter on the scan tool. If the 3X is not responding, inspect the CKP sensor B and circuits for intermittents. Inspect the ignition control (IC) circuit, IC timing control circuit, low resolution engine speed signal circuit and the low reference circuit for intermittents. If these circuits become open, or shorted, they may not set a diagnostic trouble code (DTC) immediately, but are capable of causing driveability complaints. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Test the exhaust gas recirculation (EGR) system for proper operation. Refer to Exhaust Gas Recirculation (EGR) System Description .

Inspect the Transaxle Range Switch input with the vehicle in drive and the gear selector in drive or overdrive

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Inspect for proper ignition voltage output using the following steps:

Attach the J 26792 Spark Tester to engine ground.

Connect the spark plug end of the spark plug wire to the J 26792 . Leave the other end of the spark plug wire connected to the coil being tested.

Connect the spark plug end of the companion spark plug wire to ground. The companion spark plug wire is the wire attached to the corresponding coil tower.

Crank the engine while observing the J 26792 . A spark should be observed.

Repeat the above steps for each coil.

If spark is not present at the coils, inspect for the following conditions:

Coils--Cracks, carbon tracking/arcing, or a resistance value outside the specified range

Coil Resistance
5000-8000 ohms (5K-8K ohms)
Spark plug wires--Signs of arcing, cross firing, cracks, carbon tracking, plug boot damage, pinched, improper routing, or a resistance value outside the specified range

Spark Plug Wire Resistance
9 686 ohms per meter (3,000 ohms per foot)
Important: : Spraying the secondary ignition wires with a light mist of water may help locate an intermittent problem. Ignition voltage will arc to ground when a secondary component is faulty.

Defective ignition module

Ignition system wiring--Loose ignition module feed or ground connection, or damaged system wiring

Remove spark plugs and inspect for the following conditions:

Fouled plugs



Improper gap

Burned or damaged electrodes

Improper heat range or reach

If spark plugs are gas or oil fouled, the cause of the fouling must be determined before replacing the spark plugs. Refer to Spark Plug Inspection .

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1 Answer

2004 f0rd freestar 3.9 engine it still runs slugish... i have changed 1. spark plugs 2. ignition wires 3. ignition coil 4. sprayed wire dry on harnesses and ignition wires and coil the van still...

O2 sensors get changed at 100,000 miles
Has that been done?

Has the TPS Sensor been tested with a scan tool
or oscilloscope?

Have you cleaned the MAF Sensor

All these items should be part of your preventative
maintenance,just as spark plugs

There is no need what so ever to change wires or coil,
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1 Answer

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2006 3.9 has to be a T-Bird or LS

There are no spark plug wires

It has Coil-On-Plug individual coils

Plugs don't fail --they get changed at 60,000 miles
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The front (2) O2 Sensors get repalced at 100,000
miles. The ones closest to the engine

Clean MAF Sensor at least once a year

I have no idea how you inspect a pcm,if your
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Egr Valves fail early on those & other fords

You could test,not look at,actually put an oscilloscope
on the TPS Sensor

Any oil on a spark plug requires a new valve cover gasket

If a coil was replaced based on a code alone,you may have
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1 Answer

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Is Cylinder 6 have spark now or not?

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1 Answer

96 dodge caravan 3.0 has p300 and p306 codes,

A P0306 code means that the the ECM has detected that one of the engine's cylinders is not firing properly. In this case it's cylinder #6.

A code P0306 may mean that one or more of the following has happened:

Faulty spark plug or wire, Faulty coil (pack), Faulty fuel injector, Burned exhaust Valve, Poor compression, and Defective computer. 

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 Caravan, 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). The number six cylinder is the one towards the radiator and drivers side. If you are going to change all the plugs and wire keep me posted, be glad to help. Good luck and hope this helps, P0300 just means multi miss fire. 

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1 Answer

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P1780 means that the OD switch on gear shifter was not cycled off then on during self test.
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