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EGR trouble code problems

Tiny
MAZDA626OWNER
  • MEMBER
  • MAZDA 626
My 1997 Mazda 626ES with 6 clylinder engine and Manual transmission ran great until recently, despite 197000 miles. A trouble code came up a while back that said EGR problem, so the EGR and the MAP sensor were replaced. Then the code changed to flow problem. So a set of solenoids was replaced. Don't ask what this all cost me, and the car still accelerates with a shutter at about 2500 RPM.
Now the code P0404 comes up ( P0404: Exhaust Gas Recirculation Circuit Range/Performance). My mechanic is baffled. What could this be NOW?
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Friday, October 5th, 2007 AT 9:57 AM

5 Replies

Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
EGR might be coming On too soon. Is your engine pinging/hotter than normal/Too much advance/Too lean/Low octane fuel/EGR is it OEM part/s?
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Friday, October 5th, 2007 AT 11:57 AM
Tiny
MAZDA626OWNER
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Well, I have always used REGULAR gas, despite the fact Mazda recommend Premium, and never had a problem with pinging, except very occasionally if uphill in too low a gear. But I could try changing to Premium. Not sure what OEM is, but all the new parts came from the Mazda Dealer.
What part would you change/adjust to get the EGR back in range? Is there an EGR Circuit that could be changed/fixed? I guess I could also have a tune-up.
BTW, for readers' reference: I found the Trouble Codes conversion

https://www.2carpros.com/trouble_codes/obd2
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Friday, October 5th, 2007 AT 2:34 PM
Tiny
RASMATAZ
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You need to check the entire EGR system take it out and inspect for carbon on it and its passage-VSV solenoid-vacuum going to the EGR.

Check whether the computer is activating the solenoid to apply vacuum to EGR
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Friday, October 5th, 2007 AT 7:31 PM
Tiny
MAZDA626OWNER
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Will do. THANKS!
P.S. One mechanic suggested a possible role by the ozygen sensor. Is this possible, even though that's not the code coming up?
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Thursday, October 18th, 2007 AT 7:33 AM
Tiny
RASMATAZ
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  • 75,992 POSTS
When the EGR comes in play it dilutes the A/F mix and the oxygen sensor reads it after the combustion and reports it to the computer to fine tune the mixture.

If the computer don't get the right signal from the O2 sensor, its gonna react differently.
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Thursday, October 18th, 2007 AT 4:06 PM

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