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bluehatch

In dash gauges not working properly, Please help

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I have a 86 Hatch 1.8. The car is generally in great shape but came with a few issues that I still have not been able to work out. Such as the gauges. There are other problems as well but I have been unable to discover the causes.

 

The speedo gauge is hyperactive, as i accelerate it quickly dials up and by 15mph or so is pegged at 85+ and stays there until I drop below 15mph(I guess). Thankfully I've only gotten one speeding ticket. I generally just follow the flow of traffic, however there is not always some one to follow. Lol

 

My Tacho seems to work fine until it reaches 3500+ then it starts jumping all around. Not sure what the issue is here either.

 

My Temperature gauge has only registered a temp a few times. Otherwise it never reads any temp at all. This is the one that worries me the most. I have replaced the thermostat but it did not fix it. I priced out a thermostat sending unit. But it seems cheaper just to but a new aftermarket gauge in and bypass the old.

 

I was told when I bought the car that the ECM did not work properly. (this was the reason given for why the speedo did not work) The story was that somehow oil had gotten on it and disrupted its normal function. A new one was installed but did not help.

 

So at this point the as when I bought it ECS indicator light in the dash is generally on, and sometimes the EGR light.

The engine seems runs rich, and I get 23mpg regardless of what how or where I am driving.

 

So in brief, i'm not sure where to start or how these issues relate to eachother. Please Help.

 

 

Joe

Edited by bluehatch
I miss labeled the ECM and the ECS light as ECU

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ECU? Did the 86' even come out in SPFI?

 

I thought they were all carbed untill 87' or something along those lines.

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Some of the earlier cars came with a basic ECM. I do know that it has more to do with emissions than anything else and can be removed and still pass emissions just not in California or any other place where the emissions control is highly regulated.

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ECU? Did the 86' even come out in SPFI?

 

I thought they were all carbed untill 87' or something along those lines.

 

 

Sorry about that, I incorrectly said ECU when I meant ECM. And it is the ECS light that always comes on in the dash.

Edited by bluehatch

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Some of the earlier cars came with a basic ECM. I do know that it has more to do with emissions than anything else and can be removed and still pass emissions just not in California or any other place where the emissions control is highly regulated.

 

Thanks so much for the posts. But this leaves me with the question, how important is the ECM?. Can I take it out and be fine for daily driving? I know that it deals with emissions. But I also thought it participated in controlling the air/gas mixture.

 

 

I also tried oiling the speedo cable. But it still does not function properly. Not sure what to do next with that.

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I suspect that the trouble the speedometer gauge is having is due to a problem inside it. You will need to replace the gauge itself.

 

The tach problem may be due to a bad alternator or possibly that gauge may need to be replaced also.

 

To see if the temperature sensor is responding like it should be all you need to do is remove the wire connection to it and measure the resistance of the sensor as the engine warms up from a cold start. The resistance may be approximately one tenth the value from cold to hot. If the resistance changes as the coolant warms up then the sensor is most likely ok so then there is either a wire connection problem between the gauge and the sensor or there may be a power problem to the gauge.

 

To see what is causing the engine light to turn on you should be able to connect the two connectors together that are either under the dash or the hood and read out the code errors. The connectors may be black or possibly white.

 

The rich mixture may be due to a bad coolant temperature sensor for the ECU, which is different than the one for the dash gauge. They generally have two wires running to the sensor rather than one like the dash gauge sensor has.

 

You would be wise to purchase a set of factory service manuals for this car if you are going to keep working on it. You should be able to find a set on Ebay for a good price some point in time. The set consists of 4 seperate manuals I think. The second and forth manuals, which cover the engine and wiring, are the most important ones to have.

Edited by Cougar

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I suspect that the trouble the speedometer gauge is having is due to a problem inside it. You will need to replace the gauge itself.

 

To see what is causing the engine light to turn on you should be able to connect the two connectors together that are either under the dash or the hood and read out the code errors. The connectors may be black or possibly white.

 

The rich mixture may be due to a bad coolant temperature sensor for the ECU, which is different than the one for the dash gauge. They generally have two wires running to the the sensor rather than one like the dash gauge sensor has.

 

.

 

Cougar, Thanks for the insight. I will check the resistance in the sensor for the gauge. It seems that I could also check the resistance in the sensor for coolant temp that connects with the ECU. Do you know where that sensor is located in a ea81 engine?

 

I will also start to look for the service manuals, that is a great idea that had not thought of. I will defiantly have this car as long as it runs, Ergo I will also be working on it a lot in the future.

 

After, I check out the resistance like you mentioned I guess my next step would be to find a new dash cluster.

 

I was considering just buying an aftermarket external temp gauge and bypassing the sensor, because of the price on a new thermo sensor. Is that a bad idea if the computer is getting information faulty imformation?

Or did I understand you correctly and there are TWO sensors. One for the gauge and one for the ECU.

 

Joe

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Ya, there are two sensors. One for the ECU, and one for the dash. You can bypass the dash one just fine, but the one for the ECU you shouldn't bypass. Just go to a junkyard with your DMM and test out some CTS from the junk yard if new prices are going to kill you. You can replace the sensor several times over with JY ones for the price of a new one. Just make sure you test it before you buy it at the JY ;)

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That is good news about the CTS. I will test mine out as Cougar suggested, then head for the junk yard.

 

I am in the process of replacing the heater core right now but when I get it back in and hooked up. I will replace the ECU and see what codes it is reading and continue on this process.

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