Random Cylinder Misfire

My daughters 2003 2.2L is getting the P0300 code. It ran perfect yesterday however after sitting overnight in the coldest night of the year (0F or -18C) it is running rough and giving the 300 code. I have been doing some reading here and it could be many things..plugs, fuel pressure, dirty injectors, coils, even timing chain, etc. etc.
Seeing that it was perfect yesterday, would it be safe for me to assume it is not
fuel related, but more electrical? ie plugs (originals) or coil pack or ignition control module? Any advice is appreciated. Thanks.

most likly it was moisture in the injectors/fuel that froze up overnight and when it went to start it misfired and tripped the code.
Was it running pretty poorly after it starts?

Might try some gas line antifreeze and injector cleaner.

Though if the plugs and wires are original then they too maybe part of the problem, but not the cause for the misfires IMO.

Something else to try when its realy cold like that. Put a heat lamp, infared, pointing onto the injectors and fuel lines under the hood. Not to close it could melt wiring and that would be another problem. Thaws them out quick though! :thumbsup:

Hope that helps!

1) Pull code, Reset, and clear code.
2) Monitor
3) Turn the ignition key to the on pos for a few seconds befor startup.
This will clean the MAF sensor, so a good signal is sent to the ECU/PCU for the proper air/fuel mix during the cold morning start.

1) Pull code, Reset, and clear code.
2) Monitor
3) Turn the ignition key to the on pos for a few seconds befor startup.
This will clean the MAF sensor, so a good signal is sent to the ECU/PCU for the proper air/fuel mix during the cold morning start.


I would disagree with that!
The only way to clean your MAF is with MAF sensor cleaner.

The IAT - (intake air temp) sensor is what reads temps and sends the corrisponding info, along with other sensor readings, to the PCM to calibrate A/F mix.

When the temps are below 32deg it'll run in rich mode and burn a little more fuel untill everything under the hood is warmed up. That is with the stock air box.

If you have a CAI, it takes longer for the IAT to warm up if at all. :2cents:

Or you can do a Google ''Self cleaning MAF sensor''

The MAF sensor can get contaminated with PCV oil, and dirt.
Symptoms of a cold hard start is usually a bad, or dirty MAF/IACT sensors.

If he's getting pcv oil way up there, he's got other problems.

Bosch is about the only self cleaning MAF I know of, and GM uses AC delco.
Maybe a larger engine, V8s, will have a little cleaning from the heated wires but not enough to realy make any differance without physicaly cleaning.

And IF the MAF was the problem it would throw a dtc.

Niether of which have anything to do with the p0300 random misfires. Misfires are very typical of the 3.1/3.4's and gets worse under extreme cold conditions.

You must have read an article like this off google, its 10 years old.
http://www.wellsmfgcorp.com/pdf/Counterpoint3_2.pdf

Good read, but has nothing realy to do with the 99+ Grand am MAF sensors or the P0300 DTC.

We have seen bad air filters, fuel filters, MAF sensors, dirty throttle body, and plugged catalyic converters causing random misfires.

You need a good Ignition, Air, Fuel, and exhaust to generate good horse power.

Because of age, I would focus on new filters , PCV valve, and cleaning your throttle body 1st.

most likly it was moisture in the injectors/fuel that froze up overnight and when it went to start it misfired and tripped the code.
Was it running pretty poorly after it starts?

Might try some gas line antifreeze and injector cleaner.

s!

Thanks for your reply. I am leaning towards this as the problem also, considering the fact it ran perfectly, and then not the next morning after a very cold night. Yes, it runs really rough when it starts. It will idle by itself, but missing.
I will put some gas line antifreeze and injector cleaner in, run it for a while and let it sit for a couple of days as it is supposed to warm up. Daughter can use her mother's car. If that doesn't to do it, she can drive it up the road to the garage and have them look at it.

Thanks to all who replied. Your help is appreciated.

We have seen bad air filters, fuel filters, MAF sensors, dirty throttle body, and plugged catalyic converters causing random misfires.

You need a good Ignition, Air, Fuel, and exhaust to generate good horse power.

Because of age, I would focus on new filters , PCV valve, and cleaning your throttle body 1st.

Sorry but not with these cars! :grinno:
All you mentioned, would have developed over time, not just overnight.

Though a misfire that you let continue for a long time, could kill your converter due to a rich or lean fuel condition.
And can possibly damage the ICM or other key electrical components involved within the system.

Misfires are generaly plugs/wires/coils/ICM or possibly injectors & its wiring shorting.

The car ran fine the night before a big freeze. Then the following morning it ran bad due to the misfires.

That's why I hypothesized froze injector(s).
Once it misfires the cylinder(s) involved get little or no fuel or spark, thus making it run horrible untill the problems solved.

Thanks for your reply. I am leaning towards this as the problem also, considering the fact it ran perfectly, and then not the next morning after a very cold night. Yes, it runs really rough when it starts. It will idle by itself, but missing.
I will put some gas line antifreeze and injector cleaner in, run it for a while and let it sit for a couple of days as it is supposed to warm up. Daughter can use her mother's car. If that doesn't to do it, she can drive it up the road to the garage and have them look at it.

Thanks to all who replied. Your help is appreciated.

Also have you tried clearing the code and seeing if it comes back?
That might help it run better.
If you do clear it, and the code returns, then some diagnostics is in order to find out what's exactly causing it.

Yeah I hope it warms up for you, and for me! I spend way to much of my time outdoors these days.
Im ready for summer! :D

And You are Welcome!

Enjoy your weekend guys! :cheers:

Well I put gas line antifreeze in, plus injector cleaner, and changed the plugs. (no wires to change in this odd little 2.2L) cleared the code, and ......... no luck. Still misfiring and another code 300.
Took it up to my friendly garage and it turned out to be the Ignition Control Module. Runs like a charm again.

Many thanks for the suggestions and help. Summer is on the way. We will have to see what the furry rodent says tomorrow. LOL