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400 & 402 codes come up but nothing wrong w/ EGR Valve

Mazda Millenia 1996
numbers coming up are:

301 - saying it’s misfiring piston #1 easy fix but this has happened twice in a year 1/2 any reason why this would keep happening?

400 & 402 -
but the EGR Valve looks good to my mechanic & the tube or pipe (?) to it is clean too.
any idea on what else could be in the way of the EGR Valve flow?

301 - What was the “easy fix” the last time?

400 & 402 - Check the passages to and from the valve for deposits clogging.

Show this to your mechanic

The easy fix was new spark plugs and fuel injector (was stuck open)

@ Keith- THANK YOU! A mechanic has narrowed it down to the “EGR VACUUM SOLENOID”

But - when I try to order that specific part # K5T44093 w/ that name 4 Mazda Millenia 1996 2.5
I keep getting stores saying YES they have the part but the Part Number is: 2F1189 &
Part Number: EVS174 - the pics do NOT look like the right part.
I found the right part number & photo on line - and they called it an EGR SOLENOID VALVE (w/o) the vacuum… so I’m confused- is that a different part?

You could go to the dealer for this part. The dealer will match the correct part to your VIN.

The online part numbers can be the part number used by the retailer or the manufacturer of the part, Mazda may have their own part number. As for the pictures, most of the time there is a disclaimer something to the effect that the picture is generic and may not be the actual part. Make sure they have a good return policy if you purchase online.

Thanks to Keith.

The part did not fix the problem and now the 301 code is coming up again.
(and still 400 & 402)
Exhaust like smell again while driving- headaches etc. Thought I’d nailed.
Could a misfire cause bad air in the car?
No one seems to be able to figure out the problem.

Lets try this instead.

You have to scroll down to the post. The ports that your mechanic checked are probably from the exhaust manifold to the intake manifold, not the ones in the throttle body itself. To tell the truth, this is the first time I’ve seen the EGR go through the throttle body.

If this is the problem, it could have blown the throttle body gasket, hence the headaches, and while this is a stretch, it might also contribute to the P0301.

Thank you- it makes sense- especially since nothing else has! Went to yet another mechanic and he was at a loss too.
The pictures really help on the link.
My guess is that you are right about it relating to the P301 code.
I’ll keep you posted as to the results! Thank you! is a good source of factory parts. you might try there