I have a problem with my 1990 mazda rx-7 GXL. every once in a while when it is damp or humid out my car will not start... i will turn over fine it just wont fire. I took it to my mechanic and he figures that my air map sensor gets a build up of moisture after a rain or on a warm humid day, which causes it to not send enough air through the intake to start the car..... could this be the problem or is my mechanic full of ****? if any one knows what else could be wrong i would greatly appreciate a reply.

 

the MAP, stands for manifold absolute pressure. Its not going to "send air" to your intake, simply measure vacuum in the intake. That signal then goes to the ecu to help it determine fueling requirements. If he did not actually test it and find it to be bad, i would look at other more simple things, like plugs.

 

Does it flood when it won't start?

 

he didnt test it becuase he doesnt have the right chip for my make and model of a car.... although i know its not the plugs becuase i just chanmged them less than a week ago... it doesnt flood either... it doesnt seem to be getting enough gas to start... it turns over fine... theres lots of spark it just doesnt start sometimes... it only used to do this about once every 3 months but now it does it on average twice a week and its really starting to bug me... it wont start but then i leave it sit for 1 or 2 hours and it will start fine.... although this makes it sound like it is just flooded but i am 110% sure it is not..

 

your 110% confidence may be a little off. When it won't start, have you tried doing an unflooding procedure rather than just letting it sit?

By the sound of it, you might want to shop for a new mechanic.

 

no... i know for a fact its not flooded... its been flooded many times before and this is no where near the same.... its not getting enough gas... or air to start... i only ever turn it over once so really theres no chance of it even being flooded.... at times i leave my car sit for a week at a time and iwill go out to start it and i turn it over and it wont start... how could it flood just sitting in the drive way for a week untouched? my car always starts on the first turn over all the time except when this happens.... and if i let go of the key to early before the car starts it will never start on the 2nd turn over no matter what... i dont have a clue where to even begin looking for the problem and i dont want to take it to the mazda dealership to get it checked out ebcuase it will cost me a fortune.... just thought that maybe someone might have a clue what the problem is... but maybe not... my two guesses are either the o2 sensor or the air map sensor becuase it doesnt seem to be getting any gas to start or not enough oxygen.... it only ever happens when my car sits over night or for a longer period of time... i can drive it in the morning and it will start fine throughout the day... but if i dont use it during the day sometimes it wont start at night... it seems to only do it when i leave it sit for more than 5 or 6 hours... any one have any clue?

 

Common problem on FC's is leaking fuel injectors. When you shut the car off there will be residual fuel pressure in the fuel rails. Fuel is able to squeez through and flood out your motor. I know you really don't think it is flooded, but i'm 90% sure that is what is happening.

02 sensor...no...that has nothing to do with startup.
I assume by "air map sensor" you are talking about the AFM (air flow meter), which again, the car can start (for a second or two...but not run) without.

If it isn't flooding, my next best guess would be low compression. Like I said before, i'm 90% sure it is leaking fuel injectors causing a flood.

-Marques