random misfire

big guy · 09-27-2009, 07:58 PM

This morning my '06 super charged Sol started misfiring, I was 400 km from home on sunday morning and no dealer to take it to. I slowly keept it going and picked up enough speed to get up to 100 km/h so I could travel on the highway, and it slowly got better but still was missing if I tried to accelerate to fast. My check engine started flashing once in a while but wouldn't stay on. I traveled about 350 km and had a long hill to go up and the check engine light finally stayed on. My Dash hawk indicated a random misfire code p0300, has anybody had this problem or does anyone know what the cause could be? The car idles fine and seams to run OK except for the missing when I accelerate. Will call my dealer tomorrow but I would like to help him with more info via phone.
Thanks

neilh89 · 09-27-2009, 08:21 PM

Looking at the service manual it says this:

Quote:

If the ECM detects a misfire rate sufficient to cause emission levels to exceed mandated standards, DTC P0300 sets. Under certain driving conditions, a misfire rate can be high enough to cause the 3-way catalytic converter (TWC) to overheat, possibly damaging the converter. The malfunction indicator lamp (MIL) will flash ON and OFF when converter overheating, damaging conditions are present and DTC P0300 is set. DTCs P0301 - P0304 correspond to cylinders 1-4. If the ECM is able to determine that a specific cylinder is misfiring, the DTC for that cylinder will set.

Diagnostic Aids

Quote:

A misfire may only occur when the engine is under a load or when the engine is cold.
A misfire DTC could be caused by an excessive vibration from sources other than the engine. Inspect for the following possible source:
- A tire or wheel that is out of round or out of balance.
- Variable thickness brake rotors.
- An unbalanced drive shaft.
- Certain rough road conditions.
- A damaged accessory drive component or belt.
- A damaged reluctor wheel.

It also list to check the following:

Quote:

Engine Vacuum Leaks
Fuel pressure that is too low or too high
Contaminated Fuel
Restricted Exhaust System
Spark Plugs

Did you notice any other conditions?

What is your exhaust system setup like?

big guy · 09-27-2009, 11:02 PM

spark plugs have 13,000 km on them.
Cat converter is stock.
I had just put a full tank of 94 octane in the car about 3 km before is started acting up.
no excessive vibrations of any kind.
Exhaust system is GMHP cat back.
Dash Hawk showed normal vaccum readings.
Engine was warm and up to temp.

ASETech67 · 09-28-2009, 06:30 AM

Hi Big Guy
Sounds like you are experiencing a lean misfire condition, I say this cause the only code to have set was a PO300 (Random cylinder misfire detected). If you had a bad ignition coil or a bad spark plug, or even a lean injector, you would have a DTC code with the corresponding cylinder...IE... PO301, (Misfire detected Cyl. #1), PO302 (Misfire detected Cyl. #2) etc etc...Id check your fuel pressure first, since there is a known problem with low fuel pressure via a faulty fuel pump...also look for any vacuum leaks, tears or loose clamps in your Air snorkle set up that might be allowing unmetered air into the engine that the ECU is not accomodating for in the air/fuel ratio. Just a start...let us know what you find.

neilh89 · 09-28-2009, 06:54 AM

Quote:

Originally Posted by ASETech67

Hi Big Guy
Sounds like you are experiencing a lean misfire condition, I say this cause the only code to have set was a PO300 (Random cylinder misfire detected). If you had a bad ignition coil or a bad spark plug, or even a lean injector, you would have a DTC code with the corresponding cylinder...IE... PO301, (Misfire detected Cyl. #1), PO302 (Misfire detected Cyl. #2) etc etc...Id check your fuel pressure first, since there is a known problem with low fuel pressure via a faulty fuel pump...also look for any vacuum leaks, tears or loose clamps in your Air snorkle set up that might be allowing unmetered air into the engine that the ECU is not accomodating for in the air/fuel ratio. Just a start...let us know what you find.

I would also check the stock catalytic converter since the warranty was just extended on the 2006 - 2007 models because they were becoming clogged, of course with the super charger this warranty will be voided. This at least sounds like a possibility also because it is not cylinder specific, of course I am not a mechanic so this is just a guess.

Extended Converter Warranty 2006-2007 2.4L Engines

Dave@ddmworks · 09-28-2009, 08:53 AM

Quote:

Originally Posted by neilh89

I would also check the stock catalytic converter since the warranty was just extended on the 2006 - 2007 models because they were becoming clogged, of course with the super charger this warranty will be voided. This at least sounds like a possibility also because it is not cylinder specific, of course I am not a mechanic so this is just a guess.

Extended Converter Warranty 2006-2007 2.4L Engines

This would also be my first guess as we have seen quite a few of the 06-07 cats fail. With your dashhawk email or pm me what pressure you are seeing at full throttle and if it is excessively high, that means the catalytic converter died.

big guy · 09-28-2009, 09:09 AM

Thanks for the info so far, I'm also leaning towards the Cat converter. I will try to get it off today and look in it. I was going to call you today Dave but I will wait untill I get more info from my end.

King-Oka · 09-29-2009, 01:18 AM

Hey Kyle,
I responded to your PM, but have changed my mind after reading your post. I agree, the faults sound like a bad CAT. I have a stock one you can have if you can wait for me to send it to you (couple days till I'm home). You could slam it in and see if it fixes things.

I agree with Dave - get a pressure reading and you'll know. In fact, just take the hose clamp off your unused nipple after the MAF. Give it a rev and see if you pop the nipple. If so, it's the CAT. I could not hold that nipple on without a clamp after the CAT plugged.

Bad gas, bad fuel pump and bad injectors could also be the cause, but I really do suspect the CAT first.

big guy · 09-29-2009, 09:01 AM

Talked to the mech. at the dealer and he said to bring it in just the way it is without taking anything off and he would look after it!.
I did notice when I started it yesterday that the vacuum is about 18 pounds at idle and I think it used to be about 24 pounds. Will do what Geoff suggested and see what happens.

Deep-GXP · 09-29-2009, 01:40 PM

Waiting to hear what happens...I just recently got the same codes.

LatinVenom · 09-29-2009, 06:09 PM

Mine was a broken wire in one of the coils.

big guy · 10-02-2009, 04:16 PM

Had it at the dealer today, they couldn't find anything wrong at all. Nothing on the computer except the code, so it's reset now and we will try it again. Before I took it in it was running perfect on a fresh tank of gas. The only other thing it could be is bad gas and I have no way of knowing because I used it all! Anybody have any other ideas?

King-Oka · 10-02-2009, 09:18 PM

Bad gas may be true as you had just filled up. May have got some debris or water with your gas.

oa5599 · 10-03-2009, 01:09 AM

Hello, I have had the random misfires. Found a basic problem at the coil pack connector. Pop the engine cover off. Check the wires going into the connectors to the coils. Make sure they are not overly twisted. You should see all four wires of all four packs going relatively straight into the connector from the sheathing. The person who assembled my engine must have been frustrated that day as they twisted one connector about two times before connecting it....breaking a wire inside and causing a random untracable misfire! I have seen this on one other car.