Map sensor

MY 1989 TOYOTA COROLLA ALLTRACK STALLS OUT WHEN IT IS COLD, WINDY OR A LOW PRESSURE SYSTEM OCCURS.WHEN IT IS NICE OUTSIDE THERE IS NO PROBLEM WHATSOEVER. I BELIEVE IT IS THE MAP SENSOR BUT A NEW ONE COSTS OVER $300 SO I CAN’T JUST REPLACE IT. IT HAS A 4A-F ENGINE. THE ENGINES IN THE JUNK YARD HAVE A SENSOR THAT MIGHT WORK BUT TOYOTA PUT A TAB IN THE CONNECTOR SO YOU CAN’T HOOK UP THE WRONG SENSOR.I WOULD LIKE TO ADD A CONNECTOR FROM ONE OF THE OTHER CARS BUT I DON’T KNOW WHAT EFFECT IT WOULD HAVE ON MINE. THERE ARE 3 WIRES AND THEY MIGHT BE ARRANGED IN A DIFFERENT ORDER.MY SENSOR IS NUMBER 89420 12010 AND I WOULD LIKE TO REPLACE IT WITH A 89420 12040. VERY SIMILAR LOOKING BUT NOT AS THICK. THIS WOULD COST LESS THAN 10 BUCKS.CAN ANYBODY HELP ME? THANKS, BOB

Even Dr. House uses more information than just a change in the weather to make a diagnosis! You’d be ahead if you let a mechanic take scan readings and diagnose the problem.

ALL THE MECHANICS I’VE BEEN TO ARE NIMRODS! THEY DON’T EVEN GET THE TIMING MARK RIGHT. ONLY THE SMOG GUY GOT THAT ONE RIGHT. THIS IS AN INTERMITANT PROBLEM WHICH MAKES IT FRUSTRATING.

someone needs their diaper changed.(HUGGIES I presume?)

use a DVOM! and see whats what.

and NO.

NOW THAT I’VE HAD AN EXPERT IN BABY DIAPERS RESPOND PERHAPS A REAL MECHANIC MIGHT KNOW HOW A MAP SENSOR WORKS. I HAVE A DVOM AND A CHILTON MANUAL. I’M SURE YOU ALL KNOW HOW LAME THAT BOOK CAN BE. I DON’T KNOW EXACTLY WHAT VOLTAGE I’M LOOKING FOR. I GUESS I CAN UNHOOK THE VACUUM HOSE AND APPLY DIFFERENT AIR PRESSURES ON IT AND CHECK THE DIFFERENT WIRES FOR VOLTAGE OR LACK OF IT. I’M NOT A REAL MECHANIC AND HAVE LEARNED EVERYTHING THE HARD WAY. I DO UNDERSTAND WIRING CIRCUITS AND HAVE CHANGED HALF A DOZEN ENGINES IN MY TIME. NONE OF MY VEHICLES EVER HAD A MAP SENSOR ON THEM BEFORE.

You have to use the right part number. Those tabs are there because the wrong one will give wrong readings to the computer. You are right to not want to pay $300 to fix it so cut the tab and do evil experiments. You have nothing to lose. It may not be the MAP sensor. I assume you have changed some of the other parts you could get cheaply, so I can’t point out that there may be some other sensor at fault. Do check the hot air tube going to the air cleaner housing. If that thing is broken or disconnected, cold air can stall a cold engine.

I certainly don’t think it’s a good idea to go splicing in a sensor that isn’t made for operation with that particular engine. Even if you got it to work, it could send incorrect data to the computer and not do anything to solve the problem. Might make it worse, in fact.

Where did you get the price for a new MAP sensor? In the past I’ve replaced MAP sensors for a few dollars at my local parts store. Perhaps you can do the same.

THANK YOU FOR ALL YOUR REPLYS. APPARENTLY THE TOYOTA ALLTRACK WASNT’T PRODUCED FOR BUT A COUPLE OF YEARS SO THEY PRICE THIS SENSOR HIGH. THE ENGINE IS MORE COMMON BUT PERHAPS THE COMPUTER IS DIFFERENT, I DON’T KNOW. THE PRICE WAS FROM AUTO ZONE WHICH I COULD GET ONLINE AND FIND SOME USEFUL INFO ON THE MAP SENSOR. KRAGEN DIDN’T EVEN HAVE IT. THE ENGINE IS MOST LIKELY TO STALL AFTER IT WARMS UP A LITTLE. ONCE, AFTER A BAD RAIN STORM I COULDN’T GET IT STARTED AT ALL. THAT WOULD HAVE BEEN THE TIME TO TEST IT. ALSO, YOU ALL ARE CORRECT, I CAN’T RULE OUT ANYTHING ELSE. THERE ARE SEVERAL DOHICKEYS ON THIS ENGINE I’M NOT USED TO SEEING. THIS IS JUST THE ONLY ONE I COULD SEE THAT WAS EFFECTED BY THE WEATHER. I WILL JUST HAVE TO TAKE VOLTAGE MEASUREMENTS AND PLAY WITH IT. THANKS, AGAIN.

Perhaps a sensor from a salvage yard? There’s got to be quite a few available. They may not be guaranteed, but you could try one cheaply and see if it makes a difference. Also, bad ignition components (like ignition wires and coils) can be temperature, humidity, and barometric pressure sensitive, kind of like someone with a “bad leg” that can detect the upcoming weather. Not trying to be impolite, but can you please turn off your caps lock key? In web blogs such as this, all caps is construed as shouting.

After the comment about not starting at all during a rainstorm you could possibly have a moisture induced electrical problem in the secondary ignition.

Note if there is any moisture on the coil and inside the distributor cap; especially after rain or during the early morning if it’s humid outside.
The engine is hot when shut off of course and on humid days engine heat will attract moisture. It’s the same as a house window sweating on the inside.

You can try spraying the coil, distributor cap, and plug wires down with WD-40 to see if the problem goes away.

Silicon spray is water repellent. Spray it on wires and ignition coil and map to keep the moisture out.

Thank you for your additional comments. I didn’t know the cap lock on meant I was shouting. It’s just a habit I have from computer programming. I’ll check about the moisture situation. If the junk yard had my part I wouldn’t being asking about this in the first place. But you never know, they might get one someday.

Have you tried looking on eBay? I thought I saw one there.