# Cylinder 3 misfire



## hippyfisher (Mar 24, 2009)

I know this is the truck board but you guys seem to be the ones that know the most about working on engines. My wife's 2000 Monte Carlo SS 3.8L check engine light came on and the comp says cylinder 3 misfire. The car has 173,000 miles on it and it seems to be idling a little rough but really nothing major. You dont notice any difference in the engine while accelerating. The plugs and wires are less than 4 months old and that plug still looks fine. I switched out the coil packs to see if the misfire would move to a diff cylinder and it didn't. I switched out wires and nothing changed. I put a new injector in. If you pull the power from the injector the idle gets significantly worse. I dont see any vacuum leaks and i tried testing with starter fluid and found no leaks. I used the break booster to suck cleaner into the valves and that didnt seem to help. Whats my next step? I really dont want to get a valve job done as the car is not worth that much if u ask me. Any ideas?

Thanks, Steve


----------



## BIG PAPPA (Apr 1, 2008)

*move the plug*

swap cylinder 3 plug with cylinder 5 plug and see if the miss moves. Possible Carbon Tracking. But you should be able to see that. It'll look like a pencil mark down the white Porcelian part of the plug. And just because the plug looks good, don't mean it's okay. i would next try another wire or swap wires after that.


----------



## hippyfisher (Mar 24, 2009)

Thanks for the help but neither solution changed anything. I guess i'm ready to waive the white flag on this one. Breaks my heart, i've only ever taken one other car to a shop and that was due to a transmission problem.


----------



## BIG PAPPA (Apr 1, 2008)

*this might help*

xTooltipElement








Service Information 
      

2000 Chevrolet Monte Carlo | Impala, Monte Carlo (VIN W) Service Manual | Document ID: 478456 
Cuts Out, Misses 
Checks
Action
DEFINITION: Steady pulsation or jerking that follows engine speed, usually more pronounced as engine load increases.
Preliminary
• Refer to Powertrain On Board Diagnostic (OBD) System Check .
• Refer to Important Preliminary Checks in Symptoms before starting.
• Refer to Visual/Physical Checks in Symptoms .
• Search for bulletins.​Fuel System
• Check system fuel pressure. Refer to Fuel System Pressure Test (VIN K) .
• Check the fuel injectors using the following procedures: 
 - Fuel Injector Solenoid Coil Test - Engine Coolant Temperature Between 10-35 Degrees C (50-95 Degrees F) 
 - Fuel Injector Solenoid Coil Test - Engine Coolant Temperature Outside 10-35 Degrees C (50-95 Degrees F) 
 - Fuel Injector Balance Test 
• Check for contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
• Check items which can cause an engine to run rich Long Term Fuel Trim significantly in the negative range. Refer to Diagnostic Aids for DTC P0172 Fuel Trim System Rich .
• Check items that can cause an engine to run lean Long Term Fuel Trim significantly in the positive range. Refer to Diagnostic Aids for DTC P0171 Fuel Trim System Lean .
• Check for fuel in the Fuel Pressure Regulator vacuum hose.​Sensor/System
• Check for conditions which cause an incorrect idle speed.
 - Throttle body tampering, excessive deposits, or damage. Refer to Fuel Metering System Component Description .
 - Restricted air intake system. Refer to Air Intake System Description .
 - Large vacuum leak.
• Check the TP sensor and related circuit wiring. Refer to DTC P0123 Throttle Position (TP) Sensor Circuit High Voltage .
• Check the EGR system for proper operation. Refer to Exhaust Gas Recirculation (EGR) System Description .
• Check the PCV Valve for proper operation. Refer to Crankcase Ventilation System Description .
• Check the transaxle range switch input with the vehicle in drive and the gear selector in drive or overdrive. Refer to Range Reference in Automatic Transaxle - 4T65-E.
• Check the following for damage:
 - Bent harmonic balancer interrupter rings
 - Damaged crankshaft position sensor​Ignition System
• Check for proper ignition voltage output using the following steps:
 - Clip theJ 26792 spark tester to engine ground.
 - Connect one end of a spark plug wire to the spark tester, leave the other end of the spark plug wire to the coil being tested.
 - Connect one end of another spark plug wire to the other coil tower, connect the other end of the spark plug wire to ground.
 - Crank the engine while observing the spark tester, a spark should be observed.
 - Repeat the above steps for each coil.
• If spark is not present at the plug, check for the following conditions:
 - Coils - Cracks, carbon tracking/arcing, or a secondary 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*
600 ohms per/ft.

*Important: *Spraying the secondary ignition wires with a light mist of water may help locate an intermittent problem. Ignition components will arc to ground when a secondary component is faulty. 

 - Defective module
 - Ignition system wiring - Loose ignition module feed or ground connection, or damaged system wiring.
• Remove spark plugs and check for the following components:
 - Fouled plugs
 - Cracks

*Important:: *If carbon tracking is detected on any component replace that component and it's mate. Carbon tracking on the porcelain and pitting on the plug wire contact. 

 - Improper gap
 - Burned or damaged electrodes
 - Improper heat range or reach. Refer to Spark Plug Usage in Engine Electrical.
• If spark plugs are gas or oil fouled, the cause of the fouling must be determined before replacing the spark plugs.
• Check for the following intermittent ignition system conditions:
 - Intermittent CKP 18X Signal
 - Intermittent ignition feed circuit or sensor ground circuit to the crankshaft position sensor or the camshaft position sensor
 - Intermittent 3X reference signal
 - Intermittent camshaft position signal​Engine Mechanical
• Check engine mechanical for the following:
 - Check compression
 - Sticking or leaking valves
 - Worn camshaft lobes
 - Valve timing
 - Bent push rods
 - Worn rocker arms
 - Broken valve springs
 - Excessive oil in combustion chamber-Leaking valve seals
 - Low cylinder compression
• For incorrect basic engine parts inspect the following components:
 - Camshaft
 - Cylinder heads
 - Pistons, etc.​Refer to Engine Compression Test and Cylinder Leakage Test in Engine Mechanical.
Additional Checks
• Check exhaust system for possible restrictions:
 - Inspect exhaust system for damaged or collapsed pipes.
 - Inspect mufflers for heat distress or possible internal failure.
 - For possible plugged three-way catalytic converter. Refer to Restricted Exhaust System Check .
• An engine miss condition can be caused by electromagnetic interference (EMI) on the reference circuit. EMI can usually be detected by monitoring engine RPM with a scan tool. A sudden increase in RPM with little change in actual engine RPM change, indicates EMI is present. If a problem exists, check routing of secondary ignition wires, high voltage components near ignition control circuits.
• Check for intake and exhaust manifold passages for casting flash. Refer to Intake Manifold Cleaning and Inspection and Exhaust Manifold Cleaning and Inspection .
• Check for faulty motor mounts. Refer to Engine Mount Inspection in Engine Mechanical.​


----------



## hippyfisher (Mar 24, 2009)

Wow thanks. Lots of info there. Not sure if you meant for me to, but i cant follow any of the links. It says i'm not authorized.


----------



## Samson (Aug 21, 2007)

I would test the resistance of the coils and spark plug wires. Just because the wires are new does not mean they are within spec. I just had the same problem on my '00 Mazda Millenia. New wires, plugs and distributor/coil and the car was still misfiring on cylinder #3, but ran fine above 2000 rpms. Turns out my brand new wires and coils were not within spec for the OHM resistance allowed. I went through 4 new coils before I gave up and bought a different brand. As an example my coil resistance was supposed to be between 19-21K ohms. The new coils were testing in the 18k ohm range. Not off by much but enough to make the car run like ****! Same story with the new wires. As soon as I ditched the chinese parts and bought american, my problem disappeared. Buy once, cry once!


----------



## BIG PAPPA (Apr 1, 2008)

*YEAH...I KNOW*



hippyfisher said:


> Wow thanks. Lots of info there. Not sure if you meant for me to, but i cant follow any of the links. It says i'm not authorized.


I posted the info for other things to check. I cannot give access to any of the links (sorry) but though the other items might turn on a light for you or lead you in the right direction.


----------



## Bottomsup (Jul 12, 2006)

Do a compression test before spending any more money. I have also found the idle air control valve to cause silly misfires. Sounds like she is low on compression on number 3 based on what you have tried.


----------



## hippyfisher (Mar 24, 2009)

Bottomsup said:


> Do a compression test before spending any more money. I have also found the idle air control valve to cause silly misfires. Sounds like she is low on compression on number 3 based on what you have tried.


How would you test the idle air control valve?


----------



## Bottomsup (Jul 12, 2006)

Dont know how to test it. If you have one of those pick a part yards you could get one cheap. Most of the time the computer will throw a code for it. Compression test will tell you if its worth fixing or not. Also try moving the plug to another cylinder. Carbon tracking is common.


----------



## Roby (Jul 12, 2005)

Run a compression test. If it checks out OK., you probably have a vacuum leak that is leaning out cyl. #3. Most likely an intake manifold gasket.


----------

