Baffling cold start issue....

[mabrooks12]

My Daughters 2003 Mazda 6, 3.0 liter, wont start when the air temperature is below 50 degrees F. The engine cranks over fine, but the car wont start. When the ambient temperatures are above 50 degrees it starts up and runs fine, in fact, if I use a warm water soaked rag and place it on the ambient temperature sensor and trick it into thinking the outside temp is say 65 or 70 the car will start when its only 40-45 degrees out. It also runs fine at this temp just wont start? I am a bit baffled on this...any help you can provide would be greatly appreciated by both me and my Daughter. The ambient temperature sensor seems to be working fine as it does display the correct air temperature on the dash display? I am wondering if it has something to do with the IAT sensor (part and parcel with the MAF) and the two sensors not agreeing as to what the real temp is....just not sure how to troubleshoot the IAT, have a nice fluke meter and I know what wires at involved just not sure of the ohm readings I should be getting and what temp they correspond to. Pulled the codes and it seems to indicate a problem with the throttle actuator or position sensor and either being stuck or forced limited RPM...

Any help here would be appreciated, next stop will have to be the dealer if I can nail down the problem....

Matt B.

 

[Jonota]

What were the actual codes that you got?

 

[mabrooks12]

P2107 and P2110

A few days ago it wouldnt start, so instead of warming up the abient sensor to trick it to blieve it was warm out (I believe the temp was low 50's) I disconnected the MAF (hence the IAT) harness and the car started but immediately shut down due to (I believe) MAF failure as it was disconnected, but at least it started. It seems the colder it get the worse the problem gets. I tried to start it the other day when the temps were in the low 30's and even warming up the ambient sensor had no effect, nor did disconnecting the MAF or warming up the IAT sensor...nothing worked at the very low temps. I dont want to throw a bunch of money at parts, as I am sure the dealer will likely want to do the same if he cant nail down the problem immediately....I dont want to pay him to waste my $....heck I can do that myself, but alas maybe its something simple he can fix in 10 minutes?

 

[8.5MS3]

its the throttle actuator. its malfunctioning for some reason, possibly sticking in the cold

EDIT: Found this:

Make : MAZDA Model : MAZDA6 Year : 2003
Manufacturer : MAZDA MOTOR CORP
Service Bulletin Number : 0100907 Date of Bulletin : FEB 22, 2007
NHTSA Item Number : 10021213
Component : FUEL SYSTEM, GASOLINE : DELIVERY:FUEL PUMP
Summary Description :
ENGINE NO START DUE TO FROZEN MAIN RELAY/FUEL PUMP RELAY.
--------------------------------------------------------------
Make : MAZDA Model : MAZDA6 Year : 2003
Manufacturer : MAZDA NORTH AMERICAN OPERATIONS
Service Bulletin Number : 0104004 Date of Bulletin : DEC 01, 2004
NHTSA Item Number : 10016849
Component : ENGINE AND ENGINE COOLING:ENGINE
Summary Description :
ROUGH IDLE / ENGINE STALL DURING COLD START AT NORMAL AMBIENT TEMPERATURE. *TT
------------------------------------------------------------------------------------------
theres actually quite a few. I would print the list out and tell the service dept to fix all of them

http://www-odi.nhtsa.dot.gov/tsbs/tsbsearch.cfm

 

[mabrooks12]

Throttle acuator

Any fixes for this? Could it possibly be due to a faulty TPS?

 

[8.5MS3]

mazda is obligated to fix it, you may have to pay a small inspection fee or something

 

[mabrooks12]

cold start issue resolved?

Dealer says my cold start issue (below 60 degrees) is related to a faulty PCM, and wants $750 to replace it. Not sure how it is related to the PCM as it will not start below 60 degrees.....so say at 55 degrees, it wont start....but at 60 it will? How can a bad PCM cause this? 5 degrees ? It doesnt have a temp gage in it so how does it know the temp has dropped 5 degrees? I mainatin it is a signal coming from somewhere else that is preventing the car from starting? Dont want to blow $750 on a new PCM and find out it isnt the bad part.

Any advice here would be appreciated.

 

[8.5MS3]

Dealer says my cold start issue (below 60 degrees) is related to a faulty PCM, and wants $750 to replace it. Not sure how it is related to the PCM as it will not start below 60 degrees.....so say at 55 degrees, it wont start....but at 60 it will? How can a bad PCM cause this? 5 degrees ? It doesnt have a temp gage in it so how does it know the temp has dropped 5 degrees? I mainatin it is a signal coming from somewhere else that is preventing the car from starting? Dont want to blow $750 on a new PCM and find out it isnt the bad part.

Any advice here would be appreciated.

So your ecu is shot....thats very odd. im not that familiar with older 6's but i would try to see if u can get the ecu off of a totaled 6 in a junkyard somewhere. may be worth a shot???

Also take it to another dealer, with the economy dealers are struggling and will try and rob you blind....