Hesitation / misfiring, rough idle

RPENFI77

MEMBER
2003 MAZDA PROTEGE
4 CYL
FWD
MANUAL
77,000 MILES

Hey guys,

My car has started acting up. For the last month or so the engine occasionally starts acting up (frequency has increased in last week or so) Under constant throttle, engine will hesitate and sputter, seems like something's misfiring. During this time, if I put the car in neutral, the rpm's go very low and the car feels like it wants to stall. However, this occurrence doesn't happen all the time, but seems like it occurs once the engine is warmed up. It will come and go randomly, but if I rev the car up that usually fixes it. As of today, check engine light came on, code is P0401, "EGR System Insufficient Flow Detected", but I fear this may be a symptom, not the underlying problem. HELP!

thanks,
Bob

5 Replies

KHLOW2008

MECHANIC
41,815 POSTS

Hi rpenfi77,

You are correct about the error code being the symptom as it is not refering to a specific item malfunctioning.

Possible causes
1. EGR valve carbon deposit high resulting in partial clogging. Cleaning/replacement required.

2. Exhaust passage to EGR valve is clogged resulting in poor flow.

3. EGR valve lift insufficient due to weak vacuum or malfunctioning solenoid.

This guide will help

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

Please run down this guide and report back.

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Thursday, July 31st, 2008 AT 10:28 AM

JBUZZ

MEMBER
1 POST
2001 MAZDA PROTEGE
4 CYL
2WD
MANUAL
93,000 MILES

Car has a bit of a rough idle when it gets up to temperature. I just put new spark plugs in it and a few days later this started to happen. It wont stall but did get bad enough to where the engine light came on and it was idling real low (3-400rpm)and running rough.
I got it home and put the obd2 on it and it came up with p3000? Can't remember exactly, but it was a miss-fire issue. I cleared that off. Being that I am not the smartest guy I realized that I didn't gap the plugs! Could this be the problem, or is it in need of something else that I can do myself?

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Saturday, January 11th, 2020 AT 3:54 PM (Merged)

RASMATAZ

MECHANIC
75,992 POSTS

Engine misfiring can be caused by worn or fouled spark plugs, a weak spark (weak coil, bad spark plug wire), loss of compression, vacuum leaks, anything that causes an unusually lean fuel mixture (lean misfire), an EGR valve that is stuck open, dirty fuel injectors, low fuel pressure, or even bad fuel.

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Saturday, January 11th, 2020 AT 3:54 PM (Merged)

TDWAGNERTX

MEMBER
1 POST
1999 MAZDA PROTEGE
4 CYL
2WD
AUTOMATIC
105,000 MILES

I have a 1999 Mazda Protege with automatic transmission and 100K miles. Recently, when I put the car in reverse, I noticed that the car begins to idle roughly, and if I leave it in reverse without moving, will eventually stall. If I am actively backing up (i.E. Applying gas), then it works fine. Also, in park, neutral, or drive, the engine idles fine and otherwise works normally. I've had a fuel-injector cleaning and tune-up, but it didn't have any affect. Any suggestions? Why would putting the car in reverse affect the engine idle?

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Saturday, January 11th, 2020 AT 3:54 PM (Merged)

MMPRINCE4000

MECHANIC
8,549 POSTS

Check motor mounts for excessive movement, if OK then you may have a torque convertor problem or shift solenoid.

I would probably change fluid and filter, see if that helps.