Mechanics

STALLS AT LOW SPEEDS AND ALMOST STALLS UPON APPROACHING A COMPLETE STOP, WHY?

1998 Mazda b2500 • 85,000 miles

I just bought a 98 Mazda B2500 automatic with 85,000 miles. Currently the check engine light is on as well as the ABS light. The truck starts fine. It is when I lightly press the gas pedal that it stalls unless I press the pedal further down to give it more gas. Also, it appears as if it is going to stall upon making a complete stop after I travel at speeds of 45mph and up. I took it to Auto Zone. They told me the check engine light analysis indicates it could be a vacume leak, short or open circuit, or air mass sensor. I checked the sensor and it appears brand new. I still sprayed electronic parts cleaner inside of it and on the connectors. I checked the main big fat hose and it is good. I don't know what other hoses to check. I also installed new plugs and wires. Any ideas?
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Hymefly
July 31, 2012.




What are the exact code numbers you have not code descriptions?

Saturntech9
Jul 31, 2012.
P0102

Tiny
Hymefly
Jul 31, 2012.
Your going to want inspect and make sure your intake tube clamps for the intake mass air flow sensor etc are tight. Also inspect the intake tube for cracks holes etc. Your going to also have to check all hoses intake gasket etc for vacuum leaks. So the mass air flow sensor was reolaced with a new one?

Saturntech9
Jul 31, 2012.
The sensor has never been replaced. I checked the big hose that runs from the air cleaner. It's appears intact, including the clamps. It is nice and tight. Other than that hose, I don't know what other hose to check. I'm trying to avoid having to buy a new sensor. Is there a way to check it?

Tiny
Hymefly
Jul 31, 2012.
You said the mass air sensor appeared brand new in your first post so thats why I asked if it had been replaced. Also the first thing I would check for like I said was for a vacuum leak on all the vacuum hoses not just the intake tube Also check the intake gasket for a intake leak. Did it run any different after cleaning the mass air flow sensor?

Saturntech9
Jul 31, 2012.
I sprayed some soapy water on all hoses I could see. I couldn't identify any leaks. The mass air sensor is factory original. It appears new from the inside. Nonetheless, I sprayed cleaner. It didn't make a difference. I also ran the truck with the sensor disconnected. No difference either. The air filter is ok. I had my father press on the gas so I could see the tailpipe. I noticed some extremely faint black smoke whenever the truck starts choking up as if it is going to turn off. To my limited knowledge, it appears as if the fuel/air mixture is not correct. Too much fuel not enough air?
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Tiny
Hymefly
Aug 1, 2012.
I have never heard of someone looking for a vacuum leak with soapy water.A vacuum is a negative pressure so your not going to see any bubbles using soapy water if there is a leak. What I do is get some carb spray let it idle and spray it around all the hoses and the intake gasket. If the engine stumbles rpms go up or down or the engine dies you have a leak there.

Saturntech9
Aug 1, 2012.
I'M NOT SKILLED IN THE SENSORS AND STUFF ON THESE NEWER RIGS. YET

BUT AS FAR AS SEARCHING FOR VACUUM LEAKS---SEARCHING FOR THEM HAS BEEN AROUND EVER SINCE THE AUTOMOBILE WAS INVENTED

SOAPY WATER IS A. NO-GO!

VACUUM DOES NOT "BLOW BOBBLES". IT "S. UCKS"! (BUBBLES WOULD BE INSIDE)

IT S. UCKS THRU THE LINES TO "OPERATE" COMPONENTS

YOUR PCV CONSTANTLY S. UCKS----WHERE DOES THE AIR GO?

THRU THE INTAKE AND INTO THE CYLINDERS (THE PISTON DOWN ACTION "MAKES" THE VACUUM. IN SIMPLE TERMS)

SO. IF YOU HAVE A "VACUUM LEAK"----UNWANTED AIR GETS IN, AND SORTA THROWS OFF THE AIR/ FUEL MIX IN WHICH THE ENGINEERS TRY TO MAKE AS NEAR PERFECT AS POSSIBLE. THIS "WRONG MIX" IS POSSIBLY YOUR PROBLEM. IF YOU HAVE A VACUUM LEAK

YOU MUST FIND THE LEAK--IF ONE IS THERE

HERE'S THE METHODS I KNOW: 1) LOOK! LOOK FOR IT WITH A STRONG FLASHLIGHT--LOOSE HOSE--BROKEN PLASTIC TUBING--SPLIT HOSES---LOOSE FITTING HOSES

2) TUG AND TOUCH HOSES AND PLASTIC TUBING--IT MAY LOOK FINE, TILL YOU "OPEN UP" A CRACK

3) LISTEN FOR A S. UCKING SOUND.I HAVE USED THIS MANY TIMES, A 3-4 FOOT SECTION OF HEATER HOSE/GARDEN HOSE, ONE END IN MY EAR, THE OTHER END USED LIKE A STETHOSCOPE

4) YOU CAN SPARINGLY SPRAY CARB CLEANER, STARTER FLUID, ETC, ON STUFF TO INCLUDE THE INTAKE. WHEN THIS GETS S. UCKED INTO A "LEAK"----THE ENGINE RPM WILL GO UP--OR SORTA REV FOR A SECOND OR TWO. THE ENGINE IS GETTING "EXTRA FUEL" NOW--NOT THE UNWANTED AIR. SHOULD THIS "REV" OCCUR, YOU ARE PROBABLY REALLY IN THE BALLPARK OF FINDING THE LEAK

5) I ALSO TURN ON MY PROPANE TORCH (BUT NOT LIGHT IT) I SORTA WAVE THE PROPANE IN THE SUSPECT AREAS----LISTENING FOR A "REV" AS I GO

XXX) USING METHODS "4" AND "5" IT IS BEST TO DO THIS OUTSIDE-AWAY FROM OTHER CARS--AWAY FROM FLAMMABLE STUFF!

"4" IS MORE LIKELY TO BE MORE FLAMMABLE, AS YOU ARE SQUIRTING A "FLUID" THAT COULD STICK TO STUFF AND BURN IF IT WERE IGNITED

"5" MAY ACTUALLY "LIGHT THE TORCH", IF THE GAS WERE IGNITED, BUT THE GAS DISSIPATES QUICKLY AND USUALLY DOES NOT SET STUFF ABLAZE ON THE ENGINE, LIKE A FLUID

ANYTIME YOU ARE DEALING WITH A RUNNING ENGINE---OR INTRODUCING "FLAMMABLES" ON OR NEAR IT. YOU REALLY NEED A "BLANKET" TO SMOTHER ANY SMALL "FLARE-UP" AND A OPERATIONAL FIRE EXTINGUISHER IF THE BLANKET AIN'T CUTTING IT!

BE SAFE--USE COMMON SENSE!

OK I'LL LET YA'LL CONTINUE WITH YOU SEARCH TO FIX THIS THING

THE MEDIC

CJ MEDEVAC
Aug 1, 2012.
Do not use propane from a torch very dangerous propane is heavier then air and sticks around. They do have the old school propane pop tool which is expensive that has a hose and pressing button release a small pop of propane. But I would just use some carb spray. Starting fluid I think also is too explosive. Like I said before it may stumble the rpms may go up or down or it just might die. All depends on the size of the leak and where the leak is.

Saturntech9
Aug 1, 2012.
Thank you all for your responses. Much appreciated. I tried listening for a sucking sound, but couldn't really hear anything. I will go to harbor tools and buy me one of their stethoscopes. They arent expensive at all. I will try the carb cleaner thing as soon as I get home today, also. I will report back on my findings(if any) later tonight. Based on the symptoms, what are the chances of the problem being a vacume leak as opposed to a faulty mass air sensor?

Tiny
Hymefly
Aug 1, 2012.

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