PO300 is comong up. Random misfire.. I bought a new coil and swaped em around till the skip went away.. and it didnt. I replaced the ICM last year so thats prob not it.. I will check it with a test light when i get it, just 2 be sure. It ran fine yesterday mornin. When I got into it omw home from work, i started it and it was skipping horribly. This is when I scand it then played with the coils. I dont think its a plug or wire issue cuz this am when I started it, it ran fine. I shut it off right away. then restarted it. The prob came back, and the smell of raw fuel is present. So im thinking that its either a Cam position sensor or possible EGR.. Plz help cuz I REFUSE to bring it to a shop (cuz ive rebuilt this car from the ground up) and i dont feel like replacing parts till i find the prob, that get expensive.

 

ok.. so i checked the ICM (ignition control modual).. with all the coils detatched and the key in the on position, should i be getting power to each indivdual bank on the ICM. I checked them with a test light and am only getting power to the odd number cylinders (3-5-1) .. shouldnt i be getting power to them all?
Please help..

 

What year, what engine size?

 

Duh,,,, sorry... my bad.. 99 3.8
so it isnt the ICM, just changed to new one and still only get power to odd number cylinders. Im thinking now its the PCM..

 

How old/new are the plugs and wires -- that is the first thing to be tried, check routing. NOID tested the injectors? Is that the only code you are getting? Check wiring to the ICM.

Look into extended warranties -- you might thank me later. Mine have always more than paid for themselves with my Camaros...

 

OK here is the deal with the ignition system in your car.

You have a 6 Cyl engine I am guessing and both the 3.4 and the 3.8 use the same basic system. For each coil there are 2 wires underneath. One is power and the other is ground, not even or odd. Each coil fires 2 plugs at the exact same time. The ICM always has power on the hot lead, and then drops the ground in order to fire the secondary windings on the coil. Now if you are having P0300 issues then you will not usually find that in one coil, and most often it is not even the ignition system causing the issue.

P0300 is one of the worst codes to diagnose. Things that can bring up a P0300 are:
Clogged fuel injectors,
Low fuel pressure,
bad ICM (rarely)
bad ECM (rarely)
ICM and ECM usually have other associated codes singling them out.
Glogged fuel filter.
MAF failing but not failed
MAP failing but not failed
burning oil
Corrosion on the connectors.

And many more, I just cant think about them at the moment. But you can see that there are more non ignition issues than ignition issues. There is another thread that we have here that goes into detail about the P0300 fault as well. I was talking on it last week. I hate when people come into my store and dont know what is wrong with the car and start throwing parts at it. They get mad at me when I will not return the part that they bought as a diagnostic tool. I am not selling parts so you can try to fix your car, I sell them so you CAN fix your car. So find out what is wrong first and you will buy the right part the first time. A good counterman will start asking you questions about what your car is doing and then recomend the proper replacements. I do this all the time and alot of the time I send people home with a part they didnt ask for, not the one they wanted, and the problem gets fixed the first time. I ask my customers questions. There are some parts that are not a bad idea to just throw at a car. Filters, are one of those items. If you even suspect the fuel filter is bad change it... it is $15.00 of piece of mind. Examine the car a little more, try some injector cleaner like Lucas, not the cheapy stuff like STP or the store brands. and also try to lock down more on the issue, i would steer away from the ignition side of the problem unless you start getting codes like P0301 and P0304... etc. With your ignition system you will get 2 codes if it is the coil and it will be both the plugs that the coil handles and only one if it is the wire or spark plug.

I hope this helps you get your car fixed. Also more data on your car like year and engine. I am going to go out on a limb here and say you have a 96-02 3.8L since you are getting "P" codes.

Massey

 

First of all, Massey, you are the man!
Second of all YES the P0300 code is a real pain to track down!
Here is a quick version of whats going on with my car, maybe it can help you out with yours. 2000 camaro, 3.8L, PO300 code, vast majority of the misfires on 3 & 6, New MAF, swapped the coils around, new ICM, new plugs, new wires, compression ranging from 205 to 216, holding steady at 18 lbs of vacuum, several cans of Lucas and seafoam through it, new cam sensor. Still got the misfires! The only thing I can find is maybe a relearn on the pcm? I will also put a link to my thread that Massey was helping me on. hope this might help you out, and that may in turn help me out!

https://camaroforums.com/forum/93-02-v6-tech-14/rough-idle-53686/

 

Straight from GM:

Document ID# 356694
1999 Chevrolet/Geo Camaro
DTC P0300 Engine Misfire Detected

Circuit Description

The PCM has the ability to detect a misfire by monitoring the 3X reference and camshaft position input signals from the Ignition Control Module. The PCM monitors crankshaft speed variations (reference period differences) to determine if a misfire is occurring. If 2% or more of all cylinder firing events are misfires, emission levels may exceed mandated standards. The PCM determines misfire level based on the number of misfire events monitored during a 200 engine revolution test sample. The PCM continuously tracks 16 consecutive 200 revolution test samples. If 11 or more misfires are detected during any 10 of the 16 samples, DTC P0300 will set. If the misfire is large enough to cause possible three-way catalytic converter damage, DTC P0300 may set during the first 200 revolution sample in which the misfire was detected. In the case of a catalyst damaging misfire, the MIL will flash to alert the vehicle operator of the potential of catalyst damage.

Conditions for Running the DTC

No VSS, CKP, TP, MAP, ECT, CAM or MAF DTCs are set.
Engine has been running for more than 5 seconds.
Engine speed between 550 and 5800 RPM.
System voltage between 9 and 18 volts.
The ECT sensor indicates a temperature between -6°C (21°F) and 120°C (248°F).
Fuel cutoff is not active.
Fuel level is greater than 10%.
Throttle angle is steady.
Conditions for Setting the DTC

The PCM is detecting a crankshaft RPM variation indicating a misfire sufficient to cause three-way catalytic converter damage or emissions levels that exceed the mandated standard.

Action Taken When the DTC Sets

The PCM will illuminate the malfunction indicator lamp (MIL) during the first trip in which the diagnostic runs and fails.
If equipped with traction control, the PCM will command the EBTCM via the serial data circuit to turn OFF traction control and illuminate the TRACTION OFF lamp.
The PCM will store conditions which were present when the DTC set as Freeze Frame and Fail Records data.
Conditions for Clearing the MIL/DTC

The PCM will turn OFF the MIL during the third consecutive trip in which the diagnostic has been run and passed.
The History DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.
The DTC can be cleared by using the scan tool.
Diagnostic Aids

The scan tool provides information that can be useful in identifying the misfiring cylinder. If the DTC P0300 is currently stored as DTC status Failed Since Code Clear, the misfire history counters (Misfire History Cyl #1 - #6) will still contain a value that represents the level of misfire detected on each cylinder. The scan tool displayed misfire counter values (Misfire History Cyl. #1 through #6) can be useful in determining whether the misfire affects a single cylinder, a cylinder pair (cylinders that share an ignition coil - 1/4, 2/5, 3/6), or is random. If the largest amount of activity is isolated to a cylinder pair, check for the following conditions:

Secondary Ignition Wires. Check the secondary wires associated with the affected cylinder pair for disconnected ignition wires or for excessive resistance. The wires should measure less than 30,000 ohms (30K ohms).
Damaged Or Malfunctioning Ignition Coil. Check for cracks, carbon tracking or other damage. Also check coil secondary resistance. Secondary resistance should be between 5000 ohms and 8000 ohms (5K ohms and 8K ohms).
Substitute a Known Good Coil. Switch ignition coils and retest. If the misfire follows the coil, replace the ignition coil.

If the misfire is random, check for the following conditions:

Crankshaft Position System Variation. Refer to CKP System Variation Learn Procedure . The crankshaft position system variation compensating values are stored in the PCM non-volatile memory after a learn procedure has been performed. If the actual crankshaft position variation is not within the crankshaft position system variation compensating values stored in the PCM, DTC P0300 may set. The crankshaft position system variation learn procedure is required when any of the following service procedures have been performed:
PCM replacement or reprogramming.
Engine replacement.
Crankshaft replacement.
Crankshaft balancer replacement.
Crankshaft position sensor replacement.
Any engine repair(s) which disturbs crankshaft/harmonic balancer to crankshaft position sensor relationship.
System Grounds. Ensure all connections are clean and properly tightened.
Mass Air Flow sensor. A Mass Air Flow (MAF) sensor output that causes the PCM to sense a lower than normal air flow will cause a lean condition. Try operating the vehicle within the fail records conditions with the MAF sensor disconnected. If the lean or misfiring condition is not present with the MAF sensor disconnected, replace the MAF sensor.
Loss of EBCM/EBTCM Serial Data. If the PCM stops receiving data from the EBCM/EBTCM, DTC P0300 can set due to a loss of rough road data. Check for stored ABS/TCS DTCs, especially DTCs related to a serial data malfunction. Refer to Self-Diagnostics in ABS/TCS.
Air Induction System. Vacuum leaks that cause intake air to bypass the MAF sensor will cause a lean condition. Check for disconnected or damaged vacuum hoses, incorrectly installed or malfunctioning crankcase ventilation valve, or for vacuum leaks at the throttle body, EGR valve, and intake manifold mounting surfaces.
Fuel Pressure. Perform a fuel system pressure test. A malfunctioning fuel pump, plugged filter, or malfunctioning fuel system pressure regulator will contribute to a lean condition. Refer to Fuel System Pressure Test .
Fuel injector(s) Refer to Fuel Injector Coil Test - Engine Coolant Temperature (ECT) Between 10-35 Degrees C (50-95 Degrees F) . Refer to Fuel Injector Coil Test - Engine Coolant Temperature (ECT) Outside 10-35 Degrees C (50-95 Degrees F) .
Contaminated Fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
EGR System. Check for leaking valve, adapter, or feed pipes which will contribute to a lean condition or excessive EGR flow.
Extended Idle. Excessive open loop operation caused by extended idling or short trip driving may leave deposits on the heated oxygen sensors. The deposits cause oxygen sensors to respond slowly to exhaust oxygen content, affecting fuel control and causing a misfire to be indicated at idle. This condition is not permanent. To determine if this condition is causing the DTC P0300 to be set, review the freeze frame and fail records data for DTC P0300. If the DTC P0300 occurs at high engine speeds, the condition described above did not cause the DTC P0300 to set. If the DTC P0300 occurs at idle or very low engine speeds and at engine coolant temperatures less than 80°C (176°F), the condition described above is very likely the cause of the DTC P0300 being set. The deposits on the heated oxygen sensors can be eliminated by operating the vehicle fully warm at mass air flows above 15 gm/s.

Important

If the level of misfire was sufficient to cause possible catalyst damage (if the MIL was flashing), ensure that the DTC P0420 test is completed and passed after verifying the misfire repair.

Reviewing the Freeze Frame/Fail Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.

Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table.

A condition that sets a DTC other than P0300 may also cause a misfire. If any of the indicated DTCs are set with DTC P0300, diagnose and repair the other DTC before using the DTC P0300 table.

The Misfire Current Cyl # parameter may normally indicate a small amount of activity (0 - 10 counts) but should not steadily increment during an entire 200 revolution test sample period.

Depending on the cause of the misfire, the Misfire History Cyl # counter will indicate a very large number for the misfiring cylinder(s); values for the non-misfiring cylinders will be less than 1/2 as great as the misfiring cylinder(s). When investigating a misfire, always start with the components associated with the cylinder(s) that has the largest number of counts stored in the Misfire History Cyl # counter.

Steps 5 through 12 test for conditions that can cause a random cylinder misfire.

Steps 13 through 22 test for conditions that can cause a non-random or single cylinder misfire.

DTC P0300 - Engine Misfire Detected

Step

Action

Value(s)

Yes

No

1

Did you perform the Powertrain On-Board Diagnostic (OBD) System Check performed?

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2

Is DTC P1380 also set?

--

Go to DTC P1380 Misfire Detected - Rough Road Data Not Available

Go to Step 3

3

Start and idle the engine.
Review and record scan tool Fail Records.
Operate the vehicle within Fail Records conditions.
With a scan tool, observe the Misfire Current Cyl # parameter for each cylinder.
Does the scan tool indicate a current misfire?

--

Go to Step 4

Go to Diagnostic Aids

4

With a scan tool, observe the Misfire History Cyl # parameter.

Does the scan tool indicate a large value for more than one cylinder?

--

Go to Step 5

Go to Step 13

5

Visually and physically inspect the vacuum hoses/lines for splits, kinks, and improper connections. Refer to Emission Hose Routing Diagram .

Did you find and correct the condition?

--

Go to Step 25

Go to Step 6

6

Visually and physically inspect the PCV valve for improper installation and for damaged O-rings. Refer to Crankcase Ventilation System Inspection .

Did you find and correct the condition?

--

Go to Step 25

Go to Step 7

7

Inspect the throttle body inlet screen for damage or for the presence of foreign objects that may partially block the air flow sample through the MAF sensor. Refer to Throttle Body Assembly Replacement or Throttle Body Air Inlet Screen Replacement .

Did you find and correct the condition?

--

Go to Step 25

Go to Step 8

8

Test the fuel pressure. Refer to Fuel System Pressure Test .

Did you find and correct the condition?

--

Go to Step 25

Go to Step 9

9

Test the fuel for excessive water, alcohol, or other contaminants. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .

Did you find and correct the condition?

--

Go to Step 25

Go to Step 10

10

Visually and physically inspect the PCM injector grounds, power grounds and sensor grounds to ensure that they are clean, tight, and in their proper locations. Refer to Ground Distribution Schematics .

Did you find and correct the condition?

--

Go to Step 25

Go to Step 11

11

Visually and physically inspect the following areas for vacuum leaks:

Intake manifold.
Injector O-rings.
EGR adapter
EGR valve.
EGR feed pipes.
Did you find and correct the condition?

--

Go to Step 25

Go to Step 12

12

Remove the EGR valve. Refer to Exhaust Gas Recirculation (EGR) Valve Replacement .
Visually/physically inspect the valve to ensure that the pintle is not sticking partially open. Also, inspect the EGR valve pintle and seat for carbon deposits or burrs that may interfere with the pintle closing completely.
Did you find and correct the condition?

--

Go to Step 25

Go to Step 13

13

Test for proper fuel injector operation. Refer to Fuel Injector Coil Test - Engine Coolant Temperature (ECT) Between 10-35 Degrees C (50-95 Degrees F) or Fuel Injector Coil Test - Engine Coolant Temperature (ECT) Outside 10-35 Degrees C (50-95 Degrees F) .

Did you find and correct the condition?

--

Go to Step 25

Go to Step 14

14

Visually and physically inspect the spark plug wires associated with the cylinder(s) which were misfiring to ensure that they are not damaged and are connected to the proper cylinders at the coils and at the spark plugs.

Did you find and correct the condition?

--

Go to Step 25

Go to Step 15

15

Install a J 26792 Spark Tester at the spark plug end of the spark plug wire for the cylinder that is indicated by the Misfire Current Cyl # counters or Misfire History Cyl # counters as having the most severe misfire (largest number of counts).
Jumper the spark plug end of the companion cylinder spark plug wire to engine ground. The companion cylinder is the cylinder that shares the same ignition coil (i.e., 1/4; 2/5; 3/6).
Crank the engine while observing the spark tester. Spark should be observed.
Is spark present?

--

Go to Step 20

Go to Step 16

16


Important

If carbon tracking or terminal discoloration is apparent at the ignition coil end of any of the spark plug wires, replace the affected ignition wire and the associated ignition coil. Refer to Ignition Coil(s) Replacement .

Remove and visually/physically inspect the spark plug wires associated with the cylinders that were indicated as misfiring. Ensure that the wires and boots are free of carbon tracking and the insulation is not damaged.
If a problem is found, replace malfunctioning spark plug wire(s) as necessary. Refer to Spark Plug Wire Harness Replacement .
Did you find and correct the condition?

--

Go to Step 25

Go to Step 17

17

Measure the resistance of the spark plug wires associated with the cylinders that were indicated as misfiring.
Replace any spark plug wire(s) that measure more thanthe specified value. Refer to Spark Plug Wire Harness Replacement .
Did you find and correct the condition?

3280-4921 ohms/meter(1000-1500 ohms/ft.)

Go to Step 25

Go to Step 18

18

Remove and visually/physically inspect the ignition coil(s) associated with the cylinders that were indicated as misfiring. Ensure that the coil(s) and coil towers are free of cracks and carbon tracking.
If a problem is found, replace damaged ignition coil(s) as necessary. Refer to Ignition Coil(s) Replacement .
Did you find and correct the condition?

--

Go to Step 25

Go to Step 19

19

Measure the ignition coil secondary resistance.
If resistance is not between the specified values, replace the faulty ignition coil(s) as necessary. Refer to Ignition Coil(s) Replacement .
Did you find and correct the condition?

5K-8K ohms

(5000-8000 ohms)

Go to Step 25

Go to Step 24

20

Remove the spark plugs from the cylinders that were indicated as misfire.
Visually inspect the spark plug electrodes for excessive fouling. Refer to Spark Plug Replacement .
Was a problem found?

--

Go to Base Engine Misfire Diagnosis in Engine Mechanical

Go to Step 21

21

Visually inspect spark plug insulators for cracks, carbon tracking, or other damage. Also, inspect electrodes for incorrect gap. Refer to Spark Plug Visual Diagnosis .
If a problem is found, replace affected spark plug(s) as necessary. Refer to Spark Plug Replacement .
Did you find and correct the condition?

--

Go to Step 25

Go to Step 22

22

Inspect for an engine mechanical problem. Refer to Base Engine Misfire Diagnosis in Engine Mechanical.

Damaged accessory drive belt or pulley.
Damaged driven accessory (generator, water pump, drive belt tensioner, etc.).
Loose or broken motor mount.
Did you find and correct the condition?

--

Go to Step 25

Go to Step 23

23

Test for a transmission TCC problem. Refer to Diagnostic Trouble Code Identification in Transmission/Transaxle.

Did you find and correct the condition?

--

Go to Step 25

Go to Diagnostic Aids

24

Replace the ignition control module. Refer to Ignition Control Module Replacement .

Did you complete the replacement?

--

Go to Step 25

--

25

Use the scan tool in order to clear DTCs.
Operate the vehicle within the Fail Record conditions.
With a scan tool, observe the Misfire Current Cyl # parameter for each cylinder.
Does the scan tool indicate a current misfire?

--

Go to Step 2

System OK

Document ID# 356694
1999 Chevrolet/Geo Camaro

 

Another thing could be a plugged cat. Happened to me!

 

First I just wanna say thanks. Libertyforall.. U rock,, Its like I put out an amber alert and Liberty is John Walsh..
anyways.. it ended up being my ICM.. I just replaced it last year which is why I kinda over looked it.. Thanks for all the help..