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1G How many coolant sensors on a 1G Turbo DSM?

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XC92

Proven Member
1,575
363
Jul 22, 2020
Queens, New_York
Hi all, hope you've had a not too bad winter and are enjoying the early spring weather.

It's almost warm enough around here to work on the car w/o freezing and I've continued to have idling, warm engine startup and excessive gas consumption issues plus an exhaust/gas smell that I suspect are due to a faulty coolant sensor.

Thing is that 1G Turbo DSMs have multiple coolant sensors and I'm wondering what they all are and which one is likely the faulty one if it is indeed faulty.

Best as I can tell these are the ones:
  1. At bottom of overflow tank to light up dash light if coolant is running low
  2. By thermostat to tell ECU current coolant temp (2 wire)
  3. Also by thermostat...connected to dash coolant temp gauge? (1 wire)
  4. A/C switch, located...?
  5. Fan switch
I'm guessing that probably some of these are the same sensor, and maybe I even missed a sensor. Yeah I can look it up in the FSM but I slept poorly last night and can barely function, but yesterday the car acted up again and I'd like to address this ASAP.

But do I have it pretty much covered as far as all the coolant-related sensors and if a faulty one is causing these issues, is it most likely #2?

If so, OEM or is aftermarket ok and if so which one(s)?

Finally, why are some of the vacuum hoses connected to #2 & #3 if they're already feeding data to car electronics? Double duty sensors?
 
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Thanks, so, likely #5 (from your image, not my list), if it's a bad sensor, right? And, this explains what the various sensors & valves are, so many that it can be confusing.

OEM part appears to be out of production, so any aftermarket ones you'd recommend?

But I could have sworn that there were 2 vacuum valves, with 2 pipes each. Am I thinking something else that's near the thermostat but not the thermostat? I redid it all last fall and promptly forgot it. :)

Also, my A/C no longer works, could it be because #6 is faulty, or likely something else? I mean it puts out air, just not cooled air. Unrelated but just wondering.
 
I run Standard Motors TX32 for that #5 sensor (because Standard Motors is located in my town and I have relatives that work there).
 
I run Standard Motors TX32 for that #5 sensor (because Standard Motors is located in my town and I have relatives that work there).
Thanks. Is NTK ok too? RockAuto has both and several others.

And is this a common cause of the symptoms I described? Of course only an actual diagnosis would tell me if this is it, but just wondering.
 
A bad temp sensor is usually associated with a no start or hard to start condition, so it is a very important sensor. I haven't used an NTK temp sensors although I think I have 1 or 2 Knock sensors that are that brand (it kinda sounds familiar).
 
A bad temp sensor is usually associated with a no start or hard to start condition, so it is a very important sensor. I haven't used an NTK temp sensors although I think I have 1 or 2 Knock sensors that are that brand (it kinda sounds familiar).
When cold it always starts, no problem, and idles more or less ok. But after it warms up it idles rough and doesn't always start up well unless I feather the gas pedal. Also poor gas mileage & gas/exhaust smell.

Btw why do we still call it the gas pedal when it's actually the throttle pedal, which indirectly controls gas flow via sensors and the ECU? Or am I the only one who still calls it that?
 
I am 60. It is a GAS PEDAL to me. Not the accelerator, not the foot feet, ROFL I am of the age (a better way of saying I am old) that I remember the starter "button" on the floor.
 
I am 60. It is a GAS PEDAL to me. Not the accelerator, not the foot feet, ROFL I am of the age (a better way of saying I am old) that I remember the starter "button" on the floor.
Hey, as you can guess with me being the original owner of a '92 DSM I'm not that far behind, in fact just a few months from that threshold. Almost makes me wonder what I'm still doing messing with cars let alone a 25 year old's car.

But yeah, fewer syllables for sure, but it's not a gas pedal dammit Jim. It's a Throttle Opening Mechanically Operated Control Actuating Pedal, or TOMOCAP!
 
Love it! ❤️
You gotta be our age to know who the hell "Jim" is!
"But dammit Jim, it's a flip phone not a communicator, now BEAM ME UP SCOTTY"! ROFL
 
Love it! ❤️
You gotta be our age to know who the hell "Jim" is!
"But dammit Jim, it's a flip phone not a communicator, now BEAM ME UP SCOTTY"! ROFL
Heh, all wisdom relates to Star Trek. Anyone under 40 is just a child.

Btw just tried to test the temp sensor. Way too much crap in the way to get to it w/o cutting my hands. It's too cold and rainy today to tackle it but tomorrow I'll remove whatever needs to be removed to get at it. But I'm guessing that it's bad.

I mean she's a-got to a be a-malfunctioning Jim! I cannot a-say what else might a-be a-wrong wit her! I replaced the dilithium crystals last week!
 
Well that shit worked last week Scotty...............ROFL
 
First I want to confirm that it is in fact bad. Perhaps it's ok and the wiring is bad and something else is bad. But based on all that I've read it's at the top of the list of likely culprits. I'll test it, and maybe do that silly LED to read the OBD1 code morse code thing to see if a code has been thrown (although the CEL hasn't come on but for all I know it too is bad). But I have to remove a bunch of stuff to get to it first. DSM are packed tight in the engine bay.
 
Quick followup. I replaced the bad temp sensor with a new Standard Motor one. At first the gas mileage didn't appear to improve. But I let the tank run pretty low to just when the light came on, filled it completely, and now I appear to be getting better mileage.

After around a 1/4 tank of driving, mostly on streets with lots of stop and go, lights, etc., I got around 50 miles, which comes out to around 12-13mpg and doesn't sound like a lot, but before I replaced the sensor I was lucky to get 40 miles on 1/4 tank in similar driving conditions.

The car's supposed to get 17mpg in city driving, or 68 miles per 1/4 tank, but that's under ideal conditions for a new car. If I can get it up to 15mpg with additional tunes and tweaks I'll be happy. Plus I hope to put in a decent amount of highway miles this summer once I'm done with the rest of the restoration, which will get me better mileage.

Was I supposed to disconnect the battery for a few minutes so that the ECU reset after replacing the sensor, and that might be why I didn't see improved mileage at first, and might still not be getting what I should be getting? The battery actually recently died due to the passenger door not being fully closed and the dome light being on, so I guess that took care of that for me and I'll soon find out.

Anything else I should be doing with a nearly 32 year old turbo DSM to get the mileage up? Last summer I completely overhauled the intake and exhaust, cleaning everything out, replacing all the gaskets, vacuum hoses & O2 sensor, new studs, nuts and bolts, had the injectors cleaned, etc. I overhauled the gas tank & hoses a few years ago and replaced the filter. All I can think of now is replacing the EGR & emissions sensors & valves, maybe the IAC & FIAV. Would that help? I haven't yet tuned the BISS since replacing the temp sensor.
 
Forget mikes per tank or 1/4 tank. Track MPG. It's objective and repeatable. I saw 20mpg city in a 175k car. It isn't the mileage. It's the wear. How well something is treated.
 
Are you saying that the fuel gauge isn't accurate or linear enough to be a useful way to track mpg? I actually do track mpg every time I fill up, but this is between fillups and usually I get 40 or fewer miles at the 3/4 tank point.

So, what might be worn that's causing lower mpg? I did compression tests a year or two ago and the numbers were good.
 
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