CEL Light-P0302 and P0401

[co2005sc]

Hello, I am new to this and hoping to find some answers. I have a 2007 Mazda CX-7 Sport with 150,000 miles. For about 8 months now we have had our CEL on. Below is a list of what has all been replaced over the last 6 years.

VVT/Timing Chain
We are on our third A/C Compressor!

Most recent changes(within last 2 months) due to the P0301/P0401.

New Spark Plugs-All Cylinders
Fuel Injectors-Cylinders 2 and 4
Coil-Cylinders 1,2 and 4

EGR Valve w/ new gasket-Just done this weekend.

After having all of this done, we are still getting the P0401 (EGR Code) and the P0302 (Cylinder 2 Misfire). My husband and I are at a loss as to what our next step should be. Compression test, MAP sensor, EGR solenoid valve??? We can't afford a new vehicle and need this one needs to last us until March. Any tips and advice would be greatly appreciated.

 

[co2005sc]

Also, here are several of the symptoms we are having.

Rough Idol-While at stop light or in park.
CEL Flashes when the car is trying to accelerate up a hill or when I am trying to take off.
Recently started to get terrible gas mileage.
Recently started seeing lots of white smoke from the exhaust pipe.

Thanks!!

 

[brandini]

White smoke makes you think it's a blown head gasket. Have you done a compression or leak-down test?

 

[msp5]

I would have a compression test and cylinder leakage test done before condemning sensors. and for the p0401 im reading about the egr valve being carboned up.

 

[co2005sc]

@brandini-We have not done a compression test. We were thinking this needed to be the next step. Thanks for your response.

@msp5-Yes, when the CEL light initially came on it was the P0401. We read so many forums about carbon build up and cleaning it our self before getting ripped off at the dealership. In August, my husband and I completely cleaned out everything but the light came back on. Finally this past Saturday we just replaced it but the light came back on.
I really appreciate your response.

You both have been very helpful.

 

[brandini]

I'd do a leakdown test, it will tell you the same as a compression test AND where the leak is so it could uncover a leak you wouldn't otherwise find.

Has the car ever overheated?

 

[msp5]

i'd do a leakdown test, it will tell you the same as a compression test and where the leak is so it could uncover a leak you wouldn't otherwise find.

Has the car ever overheated?

he is correct. And you egr code may also be coming on because of whats going on with the misfire as well

 

[Turbo Mandy]

It's march now. Did the car last?