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Pete, Pontiac Technician
Category: Pontiac
Satisfied Customers: 19125
Experience:  17 Years Pontiac Technician and training.
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1998 camaro: ran fine..started missing..300, 301, 302, 304, and 103

Resolved Question:

I have a 1998 camero with a LS1 engine in it. It ran fine when I left for 2 years, when I came home it started missing. The codes it displayes are 300, 301, 302, 304, and 103. It dosen't seem to miss when ideling, just when you step on it a little. It also dosn"t seem to miss at a higher RPM.

Thanks Gary
Submitted: 4 years ago.
Category: Pontiac
Expert:  Pete replied 4 years ago.

Hello,I will be glad to try and assist you with this,Welcome to Just Answer.


codes 300,301,302 and 304 are all misfire codes meaning that the engine is misfiring and the computer is picking up the misfire.


Code 103 is a mass airflow sensor code,this code can cause the other codes to set and the misfire.


I would check your mass airflow sensor and even your air filter assembly,if a nest or debris has built up in the air filter box then this would restrict the air,and cause a misfire and these codes.


If no debris or anything is found clogging the air filter assembly then I would remove and try and clean the mass airflow sensor to see if this doesn't correct the problem here.The mass airflow will be either located in line with your air inlet into the engine or on top of the throttle body.


But since this sat for 2 years there could be a good chance a nest or debris has built up in the air cleaner and air cleaner box.Let me know if you need anything else,Thanks Pete!

Customer: replied 4 years ago.

I Checked the air cleaner & box, and they were clean. The mass airflo sensor had some blsck stuff on it and I cleaned it off with alcahol. The motor still dose the same same thing. It starts popping out the exaust pipes at about 1200 RPM and quits at about 1400 RPM.


thanks Gary

Expert:  Pete replied 4 years ago.

With a popping noise like this this could be carbon build up on the valves from sitting so long,If you can drive this I would try driving it with a can of fuel injector cleaner in the fuel tank at highway speeds to see if this clears up.


Usually with a vehicle sitting like this and the symptoms you have here this could definitely be carbon build up or sticking fuel injectors to where the fuel injectors aren't spraying or atomizing properly.

Customer: replied 4 years ago.

Since I contacted you last time, I erased the codes and drove it around the block. A new code came up- 432.


Thanks Gary

Expert:  Pete replied 4 years ago.

Code P0432 Main Catalyst Efficiency Below Threshold (Bank 2) ,this code is indicating a problem with a catalytic converter.Usually this indicates a plugged or restricted catalytic converter.


I would have the back pressure tested on the catalytic converters to see if there is a back pressure/flow concern.


They shouldn't have more then 1.5 p.s.i. of back pressure through all r.p.m ranges.If one does then it needs replaced.Any exhaust shop can do this for you as well as most other shops.The oxygen sensor before the catalytic converter is removed then a pressure gauge is screwed into the port to test this.


If you have a plugged or restricted catalytic converter it will cause misfire and a mass airflow sensor code like the ones you had previously.


Most likely you will find the main source of the problem here,but I would have the catalytic converters tested first to make sure.

Customer: replied 4 years ago.

I put injector cleaner and drove it. It's no different. The car dosn't have catalytic

converters on the car. How hard is it to clean the fuel injectors?


Thanks Gary

Expert:  Pete replied 4 years ago.

The vehicle should have had catalytic converters on it at one point,they may have been taken out,if they have been taken out this can cause a concern as the rear o2 sensor(s) would be reading incorrectly and can cause this problem,this could also be why the new code you have is coming up on the scan tool.


To clean the injectors yourself the only way to do this is by what you are doing,adding fuel injector cleaner into the fuel tank,i would do this with less then 1/4 of a tank,add a bottle and then drive it to near empty,repeat this 2 or 3 times,if they don't clean up then a shop will have a fuel injector cleaner that they can hook in line with your vehicles fuel rail to directly clean these injectors.I believe the charge for this is about an hours or two labor and the cleaning solvent as well.

Pete, Pontiac Technician
Category: Pontiac
Satisfied Customers: 19125
Experience: 17 Years Pontiac Technician and training.
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