Kia misfiring

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  #1  
Old 10-15-03, 06:10 PM
fishous
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Kia misfiring

Have a 2000 Kia Sephia w/manual trans, 4 cylinder. Engine began misfiring and the check engine light came on. Misfiring occurs at all speeds. Did a diagnostic scan and trouble code was P0303, cylinder #3 misfire detected. I have put in a new set of plugs (after engine light came on). From what I have read the problem could be 1. bad plug wire 2. bad coil 3. defective fuel injector.
I'm a novice. How do I check these three and what else should I check?
 
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  #2  
Old 10-15-03, 07:40 PM
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The quickest way to check whether it's the plug is to swap 2 of them. Take #3 and put it into #1, and #1 into #3. Clear the codes, and redrive. If the code comes back, but is now p0301 (misfire #1) then the plug is no good. If the code comes back the same as origanal, (p0303-#3) then swap plug wires the same way as you did the plugs. Clear the codes retest. If the code then comes back again as p0303 you've pretty much pinned it to the injector and/or injector wiring for #3.
This "method of testing" is base on the asumption you don't have access to scanners and scopes, but is also a valid test recommended by Snap-On scanner for many drivability problems...
 
  #3  
Old 10-15-03, 07:49 PM
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There are alot of variables to check for when you have a misfire code. This is the diagnostic procedure from Alldata. It is basically saying check for vacuum leaks and electrical problems. Pretty in-depth, but effective if you know what you are looking for.
INSPECTION
IMPORTANT! Record all freeze frame data
before disconnecting any connectors or
clearing code(s).

1. Check for any split, disconnected or perforated vacuum hoses. Also, check PCV valve fpr proper operation and Purge Solenoid Valve (PSV) for proper Installation and operation.
Are vacuum hoses, PCV and PSV okay?

YES - Go to step 2.
NO - Replace faulty vacuum hose(s), PCV or PSV.

2. Disconnect C131 from CKP. Measure resistance between C131-1 and C131-2 at CKP pigtail (800 to 900 Ohms at 68 degrees F). Remove CKP Sensor from transmission and calculate air gap between sensor and flywheel torque converter (0.037" to 0.067" -
0.95mm to 1.7mm) [measure distance from housing to teeth on flywheel/torque converter (measurement "A") and from mounting surface on sensor to sensor tip (measurement "B") - subtract "B" from "A" = air gap].
Are air gap and resistance measurements within specification?

YES - Thoroughly check for loose, bent or corroded terminals between C131 (CKP Sensor) and C254(ECM). Measure resistance between C131-3 and GND (< 1 ohm). Repair as necessary. If okay, go to step 3.

NO - Replace CKP Sensor or call tech line if air gap is out of specification.

With ignition off, disconnect C137 from coil packs. Turn ignition on and measure voltage at C137-1 and C137-2 (B+).
Is battery voltage available?

YES - Go to step 4.

NO - Check for open between C137-1,2 and C192-36. If wiring is okay, check for loose, bent, misplaced or corroded terminals at C137-1,2 and C192-36. Repair as necessary.
Hope this is helpful to ya,
Billy
 
  #4  
Old 10-16-03, 06:35 AM
fishous
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I think I can rule out the plug as I already replaced and still get a misfire. Would the fact that I only get a misfire on cylinder three help narrow down what the potential problem is?
billys68ss, I appreciate your response but as stated I am a novice and don't have any idea what C131 is or the ckp ( is this the crankcase position sensor?)
If that is the problem why is it in only one cylinder?
 
  #5  
Old 10-16-03, 07:38 AM
Joe_F
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If you hook a timing light onto the spark plug wire, do you get an erratic fire on the wire? How many miles on the vehicle?

Plug wires going bad are a definite possiblity.
 
  #6  
Old 10-16-03, 09:19 AM
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Yes CKP is the Crank Position Sensor. C131 is the connector to the CKP. C131-1 and C131-2 are the 2 terminals (pins) in that connector. It is telling you to check resistance from one terminal to the other. Do you have a circuit tester? If so, take the wire and clip it to a good ground point and stick the pointed end onto the spark plug (with the engine running) and notice the difference. There are many things that can cause a misfire. From bad plugs or wires to a vacuum leak near that cylinder to a dead cylinder. I have seen all of the above. You cant rule one out without proper diagnosis.
Hope this is helpful to ya,
Billy
 
  #7  
Old 10-16-03, 05:00 PM
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In addition to the advice given by the other gentlemen, I would still swap plugs around. A box of spark plugs can go through all sorts of handling before you ever get 'em. I've had it happen MANY times, a brand new plug was cracked and cause a misfire..I've seen delivery people toss the sack with the plug on the floor, like they were throwing down a dirty rag.. It's a simple check, and might just save you LOTS of headaches..

My cent...
 
  #8  
Old 10-16-03, 05:47 PM
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you should remove all plugs and check for carbon tracks down the side of the spark plug porcelin, you should also look inside the plug wire boot and coil boot for any carbon tracks look for any holes burnt in the plug wires usually show a small white spot indicating a hole in the plug wire. even though the plugs are new it can form a carbon track very quickly on a new plug if plug wire boot or coil boot has a carbon track. common problem on this model car.
 
  #9  
Old 10-17-03, 01:11 PM
fishous
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fixed

Thanks for all your help. It was the plug wire on cylinder #3. They're expensive!! Thaks again to those who replied.
 
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