Question about 2005 Ford Expedition

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Keep getting P0308 code misfire

Changed the ingnition coil #8; spark plug and wire for # 8 compression test good, no white smoke from exhaust - no smells from exhause. car rides rough when idle - hestitates on excelleration. engine skips on freeway!

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  • Rhonda
    Rhonda May 12, 2014

    Thank you so much! i will update the results to the update of replacing the fuel injector.



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A misfire code is set because one of three things is missing or not right: spark, gas, or compression. You checked compression and it's good, equal to the other cylinders? And there is spark on #8? That leaves a fuel problem, then. How does the spark plug look on #8- if the appearance is white, almost a blistered look to the bottom of the plug, that is an indication of lean running- not enough gas in the mixture at that cylinder. You may have an injector problem on #8.

Posted on May 12, 2014


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SOURCE: vehicle came in for check

A misfire at idle that smooths out at cruise is ALMOST ALWAYS caused by a vacuum leak. Take a hard look at your fuel trims at idle. If the Bank 2 Long Term Fuel Trim is more than + a couple points higher than the Bank 1 trim, your problem is most likely a vacuum leak. If the Fuel Trims even-out while holding the engine at 2000 RPM for about 20 seconds, then a vacuum leak is DEFINITELY your problem. I would suspect a leaking lower intake gasket leak because an upper plenum leak will normally affect all cylinders.

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SOURCE: 1993 Ford Explorer idles rough when engine is warm

try changing distributor cap & coil

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SOURCE: l998 ford explorer check engine light came on

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SOURCE: 2004 ford ranger edge has blinking check engine

have the crank sensor check for erratic operation. if you have done all of that then there is nothing else. and they way the computer knows it is misfiring (if it is) false code maybe and could be bad crank sensor. good luck

Posted on Oct 25, 2009

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06 4.7l dakota new plugs,coil pack,switched injectors, compression good no oil in water or water in oil still check engine light ( # 8 misfire) Dodge dealer saying either head or shot engine

You're changing/swapping a lot of parts, but are you getting spark on #8 - at the plug? Is the injector actually getting a firing signal (use a noid light to check)? Can you actually hear the engine missing/skipping, or are you basing this all on the CEL and (presumably) P0308 code?
If the compression is good (as good as the other cylinders), and you are getting spark at the plug, and the injector is getting a good signal, I don't understand the dealer diagnosing a bad head or shot engine. These would indicate a mechanical problem and compression would be the indicator.

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2001 toyota tundra 4.7l has engine code p0308

Code 0308 indicates a misfire was detected in cylinder 8. You say you checked the fuel injector and it is OK. Other probable causes include:
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1996 Lincoln Mark VIII has engine misfire on number 8 cylinder

THis is the same that P0308 fault code when "check engine" light turn on. A P0308 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 #8.

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 P0308 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
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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 this helps; also keep in mind that your feedback is important and I'll appreciate your time and consideration if you leave some testimonial comment about this answer.

Thank you for using Fixya, and have a nice day

Dec 19, 2011 | 1996 Lincoln Mark VIII

1 Answer

Engine light comes on code 308

P0308 is cylinder misfire detected, cylinder #8. Causes can be: bad spark plug, bad coil pack, faulty fuel injector, poor compression, faulty computer..I generaly recommend changing spark plugs first. Then test the coil pack, after that I would look at the injector, I have never seen a bad computer throw this code.

Jul 27, 2011 | 2004 Ford F150

1 Answer

308 code i change sparks ignition coil same problem

Code P0308 - Cylinder 8 Misfire Detected

Possible Causes:
- Improper spark plug at cylinder #8
- Insufficient compression at cylinder #8
- Incorrect fuel pressure
- The injector circuit is open or shorted at cylinder #8
- Fuel injector #8 may be faulty

Possible Solutions:
- Perform Injector Service
- Replaced Spark Plug #8
- Replaced Injector #8
- Replaced Ignition Coil #8

Jan 14, 2011 | 2000 Ford Expedition

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.

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1 Answer

Po308 code misfire #8 cylinder. How to fix? replace ignition module first? spark plugs were just done and seem fine.

Seems you may have answered your own question.

P0308 will normally be a coil failure but can also be a compression fault caused by a sticky lifter etc or a faulty, incorrectly gapped spark plug

It most likely be the coil but check the spark plug and run a compression test if you have the equipment, all bores should have equal PSi readings.

Or you could try moving the coil in cyl. 8 to see if the code moves to a different P030* code

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It's detected a Misfire in Cylinder # 8
Any of the following could cause a misfire:
faulty spark plug or wire
faulty coil
faulty fuel injector
poor compression
defective computer

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