Strange Issue ...

SP33D

Member
:
Black Mica MSP
Ok, so I just had a used motor installed in my car to replace my MSP motor.. because the MSP motor was knocking real bad. So we get it all hooked up and now I have a strange problem..

Basically when you start the car it idles funny.. constantly trying to stall out.. it will rev down and sometimes rev back up before it stalls out, or it will just stall out. Well my mechanic was checking all kinds of stuff to figure out what's going on, well he unhooked the coolant temp sensor and suddenly the car runs amazing.

So basically it runs great with the sensor unplugged, but when its plugged in.. the car runs like crap. My mods are listed in my signature. I don't really know what the problem could be.
 
no codes?
the only thing that i can think of that would cause that relationship with the coolant temp sensor is if it is seeing too cold of a value for the coolant and forcing a rich condition to try and warm the car up, thus causing fuel fouling. but even that shouldnt really cause that kind of stalling.
 
without a temp sensor in the car is in cold-startup mode....its probably maf/etc issue

not true- if it is unplugged from the ecu, then yes i suppose it would be in cold startup. But if the temp sensor is just out of the intake pipe, no big deal. It'll just read hotter/colder temperatures than actual intake temps, depending on the temp of your engine bay. Many people who have converted to SRI's have run their cars without issue just letting that little temp sensor guy hang there.

Although this is a very odd problem, usually the results shouldn't be that dramatic plugged in/versus not plugged in. how are the spark plugs? and is the maf for sure working, plugged in, and facing the right direction?

edit: eh, disregard this...coolant temp sensor is different than intake temp. im retarded.
 
um so what could it be? im thinking when its in cold start mode wouldn't it be trying to give it extra fuel... so maybe when the sensor is plugged in theres not enough fuel so it's stalling out? im really just guessing at this point... because im clueless. can anyone point me in the right direction of maybe someone that would know? because come monday i have no ride to work :eek:
 
Could be a bad ground as well on the engine harness. It can screw up the resistance values that the sensor reads causing funny runing issue since the sensors are kind of touchy. When you unplug it the car drops into fail safe for a value and runs ok. I would check the EFI harness to make sure the grounds are ok.
 
Could be a bad ground as well on the engine harness. It can screw up the resistance values that the sensor reads causing funny runing issue since the sensors are kind of touchy. When you unplug it the car drops into fail safe for a value and runs ok. I would check the EFI harness to make sure the grounds are ok.
+1
 
i would replace the IAC, a bad one will cause the engine to want to stall out.
Hey Tech,

Are you talking the whole IAC valve assembly or just the actuator? Mazda, Checker and Auto Zone only sell the whole valve assembly for around $500. I've been looking for just the actuator but not having any luck.

Thanks.
 
I was talking about the whole assembly. Yea they are expensive.

why don't you try getting one from a junk yard off a regular protege im sure its the same. it only takes like 5 mins to take it off.
 
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