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  #1  
Old 10-01-2012, 04:44 PM
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Default Mazda B4000 rough idle when warm

I have a 1996 Mazda B4000 SE 4x4 automatic. The truck sat for 8 years. It is in great shape as it was a southern truck or else id scrap it. I am having some issues with the truck idling and also with the fuel economy. When i am running around town if i run into a place and come out within 15 mins or so (not long enough for the engine to cool all of the way down) the ol girl idles pretty rough. It never stalls but feels likes it is going to. If i put it in gear and drive it 10 feet and put it back in park it will idle fine. Also if i rev it up to about 2500 rpms for 30 seconds it will also idle fine. There is one code P0402. I took the truck to Auto zone(my brother works there) and used there 150$ obd2 diagnotic tool. It told me that my IAT was reading -10 and that my engine temp was 120 degrees F. Also my guage on the dash bouncing all over the place. I did a fool coolant system flush with a kit twice about 2 months ago and replaced the thermostat both times. Yesterday I replaced the IAT sensor and both the Engine temp sensor that feeds data to the ECM and the temp sender for the guage. I installed new plugs in it about 6 months ago. I bought whatever plug was recommended by FORD. I also replaced the Idle control unit that bypass the throttle body when itis just idleing I am getting between 14-16 MPG which seems low to me and I cant get the CEL to go out. I am afraid to repalce the EGR valve as i do not want to mess up the small metal pipe that is hooked to the bottom. It looks pretty rusted on there. Can anyone help me
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  #2  
Old 10-01-2012, 04:54 PM
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Default Re: Mazda B4000 rough idle when warm

Start with cleaning your IAC valve.
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2002 ford ranger FX4 Off Road | 4.0l v6 | Flowmaster 40 S/I D/O | JBA Headers | Sno-Way snow plow mount | K&n Drop-in filter | TwinStick | 31 Spline 4.10 Torsen rear diff | Alcoa rims | Sitting on 31's|
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  #3  
Old 10-01-2012, 04:56 PM
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Default Re: Mazda B4000 rough idle when warm

the valve IAC valve I bought from autozone has a life time warranty so i just replaced it a week ago. It made no difference
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Old 10-01-2012, 05:04 PM
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Default Re: Mazda B4000 rough idle when warm

Quote:
Originally Posted by matthewavogt View Post
the valve IAC valve I bought from autozone has a life time warranty so i just replaced it a week ago. It made no difference
You could have a vacuum leak or your alternator could be going bad.
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Old 10-01-2012, 05:10 PM
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Default Re: Mazda B4000 rough idle when warm

i sprayedthe vaccum lines down with ether and couldnt find a leak tomorrow ill go have the alternator tested
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  #6  
Old 10-01-2012, 05:52 PM
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Default Re: Mazda B4000 rough idle when warm

any one have thoughts on my fuel ecconomy?
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  #7  
Old 10-01-2012, 06:01 PM
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Default Re: Mazda B4000 rough idle when warm

Are your brakes acting weird? it could be leaking around the booster.
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  #8  
Old 10-01-2012, 06:46 PM
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Default Re: Mazda B4000 rough idle when warm

The brakes seem to be ok. And because i am anal i just drove to the nearest autozone which is about 20 miles away and had them test my alternator and battery. Both tested fine. I am wondering if the DPFE could be causeing the EGR based problems. If the dpfe is bad i wonder if that could be causing be bad ideling because the air to fuel ratio is of and if that could be causeing my fuel economy issue assuming there is one

----------

i also would like to add that I do the seafoam treatment about once every 4 months.
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  #9  
Old 10-01-2012, 07:09 PM
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Default Re: Mazda B4000 rough idle when warm

Quote:
Originally Posted by matthewavogt View Post
The brakes seem to be ok. And because i am anal i just drove to the nearest autozone which is about 20 miles away and had them test my alternator and battery. Both tested fine. I am wondering if the DPFE could be causeing the EGR based problems. If the dpfe is bad i wonder if that could be causing be bad ideling because the air to fuel ratio is of and if that could be causeing my fuel economy issue assuming there is one

----------

i also would like to add that I do the seafoam treatment about once every 4 months.
Ease down on the seafoam. You don't need to do it that often.

Check the EGR. If that tube is rusty, it could have a hole in it.
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