2000 Pontiac Firebird

[Susieq]

My son has a 2000 Pontiac Firebird with a check engine light on. The codes were scanned and they are p0405 and p0300.  Any ideas or insight would be greatly appreciated. Thanks!!

[Macgyver55]

Is it the V6 or V8 motor? The V6 of that vintage had EGR valves that would often carbon up and stick and/or fail causing a random misfire and rough idle. 

[Susieq]

It is a 3.8 v6. Is there a way to clean the EGR or should it be replaced? 

[Jeremy airjer W]

Typically the engine will run a little rough at idle if the EGR is stuck a little open. You will see a metal tube coming out of the EGR valve. if the tube gets hot (carefull as it can burn you) while the car is idling than the EGR is likely stuck open a little.

Removing the valve and cleaning/soaking in carb spray may help. You will likely see a lot of carbon around the pintle. You may even see that the pintle is being held open a little by a chunk of carbon.

[Susieq]

My son replaced the EGR valve and it is still sputtering, gets terrible gas mileage and slow to accelerate. He also replaced fuel filter, spark plugs and wires.

 

 

Edited July 5, 2015 by Susieq

[Jeremy airjer W]

I think this none might be old enough to try this trick. unplug the MAF sensor. if the symptoms are noticeably less obvious than it might be worth cleaning it or replacing it with anything but a re-manufactured one. it is also common for the pigtail or connector to go bad on these as well. typically you can wiggle the connector and get it to either act up or stall. 

[Susieq]

That little tube under the EGR is hot when the car is idling.  So you think it still has something to do with the EGR??   We unplugged the MAF and it maybe changed the idle a little but not real noticeable. 

[Jeremy airjer W]

The EGR tube should be checked at a cold start. If it gets hot shortly after start up than I would suspect there is still something wrong with the EGR system.

 

I think at this point some scan tool data would be beneficial. A couple of things I would be interested in seeing is the upstream (sensor 1) O2 data, Short term fuel trim, and misfire counters if available.

 

At this point I am wondering if there is a plugged catalytic converter. Easy enough to check with a backpressure gauge. Or the red kneck back pressure test would be to drop the exhaust from the manifold and take it for a quick test drive.

[Susieq]

He changed the coils and it now runs like a peach!! He is very, very  happy. Thanks for all the help!!

[Jeremy airjer W]

Well that was easy, relatively speaking....

I guess I assumed that spark was checked. Should have recommended that right off the bat.

Glad he has it purring like a kitten!!