Mechanics

CHEVY MISS FIRING

2005 Chevrolet Impala

Shakes or Wobbles problem
2005 Chevy Impala 6 cyl Front Wheel Drive Automatic 100558 miles

I have change my spark plugs and wires, the fuel filter too. My car is still miss firing, what do I do and can I fix it my self?


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Theboss78229
October 8, 2009.



Is your check engine light on? Have you had the computer scanned? If so what are the codes? If you haven't had it scanned most major auto parts stores (autozone, advance, etc) will scan it for you free of charge.

There are many Things that can cause a miss fire, it could be fuel related, ignition related.

Please post a little more info and we will do our best to help you.

Thank you and I look forward to helping you.

Dan

Danauthier
Oct 8, 2009.
I have had it put on auto zone machine the code was 300 which is random miss fire

Tiny
Theboss78229
Oct 9, 2009.
The p0300 is helpful, if it was a specific cyliner or cylinders miss firing the codes would indicate which ones (p0301 is cyliner one and so on) This indicates all cylinders are miss firing. You have elliminated plugs & wires (used correct plugs, gapped them properly, made sure connections were clean, wires seated properly and replaced your fuel filter)

Have you checked fuel pressure? The fuel pressure, with the key on engine off your pressure should be between 52 - 59 psi. Low fuel pressure would cause your symptoms.

Do you have an aftermarket alarm system or remote start system on your vehciel? There is a GM Technical Service Bulletin (#02-06-05-400B) for your car about aftermarket alarm systems causing a missfire and damage to the catalitic converter.

Hope this helps, let me know.

Dan

Danauthier
Oct 10, 2009.
I do have an alarm system on it. Ok the check engine light went away, now all it does is fall dead on me. Could that be the mass air sensor or something like that?

Tiny
Theboss78229
Oct 11, 2009.
There is the GM Technical Service Bulletin about aftermarket alarm systems. I only have TSB's available to me in a. Pfd (adobe reader) format and have not been able to successfully post them on here. Send me a private message with your e-mail address and I will send you all the information I have.

As for the mass air flow sensor, with only a P0300 code it is not a " usual suspect.&Quot; A faulty mass air flow sensor will normally give a code for the mass air flow sensor, a code for running rich/lean or a code for poor converter efficancy. You can check the screen at the opening to the mass air flow sensor (remove the fresh air intake from the mass air flow sensor and there will be what looks like a window screen covering the intake part of the sensor), if it is dirty you could carefully remove any dibris with a shop vac and clean the screen by spraying it with a " fuel injection safe" choke and carb cleaner. Also be sure to check and change your air filter regularly.

Do you have the ability to check your fuel pressure?
This is a very important to any drivability diagnosis. As I posted earlier it should be between 52 to 59 psi with the key on, engine off.

For information purposes, what part of the country do you live in. Most people do not factor this into the equasion, but different regions have different fuel mixture. If you live in the midwest where E85 fuel is prevelant and your vehicle is not flex fuel rated you should not use E85 fuel, the high alcohol concentration can give you drivability problems like you describe, also long crank time and no start situations. Fuels in the N.E. (Where I am) have a large concentration of sulfer that can cause drivabilty problems and problems with the fuel level sensor.

Just a few more ideas. Send me that message with your e-mail and I will get you some more info.

Thank you,

Dan

Danauthier
Oct 12, 2009.
I had them put the machine on it, and it was miss firing from 5 and 6 cyc. They said it might be the alarm that I had put on it about a month ago. The alarm is autopage.

Tiny
Theboss78229
Oct 12, 2009.
According to the TSB an aftermarket alarm/security/remote start system may draw power away from the ignition system causing a missfire.

Any missfire left untreated will allow raw fuel into the catalitic converter and damage the " honeycomb" filter in the converter. What happens is the raw fuel burns once it hits the high temps of the converter, which melts the filter causing it to clog.

I would recommend disconnecting the system and see if your drivability concerns dimminish.

Just a thought, let me know.

Thanks.

Dan

Danauthier
Oct 12, 2009.
It was my fuel injection regulator.

Tiny
Theboss78229
Oct 15, 2009.
Thank you. I just looked back though my posts and realized it didn't mention that, I am sorry. I ususally post that with the fuel pressure spec's and saw I didn't do that with yours.

Glad you have it fixed.

Thank you,

Dan

Danauthier
Oct 16, 2009.