tough coolant temp sensor prob. search results inconclusive

[jasonlee]

here is the problem....

my guage in my car shows full hot all the time for the coolant temp... unless i unhook the sending unit plug, then it drops to zero....

so, we hooked up a data logger, and it shows the car is reading 419 degrees.. all the time...

i am assuming this is the max temp it will read thats why it stopped there.

i replaced the coolant temp sensor, and it still has the same problem.

on one other note... the two wires that go to the coolant temp sensor (black and black with white strip) if i unhook the black wire, my car almost dies... right away... and the air flow meter on the datalogger shows it drop to zero and the stock boost gauge drops to zero.

the other wire, if i unhook it or hook it back up (black with white stripe) it switches from a -40 to +419 WTF????

only thing i can think is maybe the ecu's temp circut is fried?

i have a 97 ecu and wiring harness.. with a 6 bolt swap..

please help!!. also my interior fans (heater and fresh air) dont work at all :-(


j

 

[JATBarandgrill]

hmmm...thats weird. Did you check fuses?

 

[SlowSpyder]

you probably have a short somewhere. run a new wire from the ecu, wire # 83 to the ect. That *should* fix the ect problem. One question, do you have a real hard time starting your car when its cold? Most likely its a short or basically the wire from the ecu to the ect is being grounded somewhere

 

[jasonlee]

well, i tried that, and it still showed the same..

and yeah, my car is tough to start pretty much all the time... takes 3 or 4 tries..

one other thing, my fuel pressure always bleeds off to zero when my car sits for a length of time, like overnight

 

[JATBarandgrill]

most likely leaky injectors. Or you could have bad o-rings where the line meets the fuel rail.

 

[jasonlee]

i cant find fuel leaking anywhere....

but the tough part is the coolant temp sensor.. wtf?

 

[SlowSpyder]

reason why you have a hard time starting the car is because the ecu is seeing a coolant temp of 419 degs. The ecu will create a lean mixture due to the high coolant temps, basically not enough fuel to start the car in the morning or when its cold. You said you replaced the ect already right? from my experience that when the ecu sees more than 300 degs from the coolant temp sensor its caused by a short. you have some sort of electrical problem or short. Are you getting any codes?

 

[jasonlee]

yeah, o2 code, but thats cause i have the plx wideband o2... wired without the little resistor for the o2 heater...

and the coolant temp code

i tried to hardwire the coolant temp sensor by cutting the wire at the ecu.. but it didnt change...

the dash guage for coolant temp also shoots straight up, and thats a separate circut... ahhhh this is stupid!!

if i unhook the sender wire the temp gauge drops... but the temp still reads 419.... but if i unhook the wire to the temp .. it reads -40 and the car then reads 0 air flow and the boost gauge drops too

wtf

j