Honda and Acura Model Specific Forums

IHEARTMYHONDA91 · 10-20-2009, 09:05 AM

I just bought an '87 Honda Civic SI...

... it runs awesome and has no major issue other than when I shut the car off, it wont start right back up, I have to let it sit for a good 20 minutes before it will fire back up!

The PGM-FI light is on and the person I got the car from said that he thinks its one of the injectors (doubt it) another buddy of mine that knows his Honda's said that its more than likely the main realy, if it has one.

My question is, do these cars have main relay's? Has anyone else ever had this problem? And is the PGM-FI light just an old school version of the check engine light?

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night · 10-20-2009, 09:23 AM

fuel injected = main relay

stick your head under the dash, upside down, and with a small flashlight look way up to the left behind the fuse box. you see an ~3x2" block with an 8P plug. next time it doesnt start tap on that with a screw driver while you turn it over.

E-AT_me · 10-20-2009, 11:24 AM

if it is the main relay, when you turn the key to position "two" you will not be able to hear the fuel pump prime..

this does not throw a code so it won't be what's wrong with the check engine light, or PGM FI light.. you have to pull that code from under the passenger seat. there are 4 LED's and depending on which ones are lit is the code #.

IHEARTMYHONDA91 · 10-20-2009, 11:42 AM

ok well I checked the ecu and 2 lights are on constantly... 4 and 2

what is it?

E-AT_me · 10-20-2009, 04:53 PM

you know, i really wish i could post the website that has a service manual on this web board, but they block it..

so i will tell you the code is for a "TW Sensor" issue.. let me guess, when you get the car running, it has a high idle speed? it's your intake temp sensor..

IHEARTMYHONDA91 · 10-20-2009, 08:41 PM

Quote:

Originally Posted by E-AT_me

you know, i really wish i could post the website that has a service manual on this web board, but they block it..

so i will tell you the code is for a "TW Sensor" issue.. let me guess, when you get the car running, it has a high idle speed? it's your intake temp sensor..

no the car actully idles and runs just fine once its started...

i just need to figure out what the codes are for...

can i have the main relay checked at autozone or something?

night · 10-20-2009, 10:44 PM

are you sure you are reading that code right?
2 and 4 is the middle 2 lights, it is binary.
and i'm showing that as the coolant temp.

i'm assuming EAT just typed the wrong thing or he read positionally 2 and 4.

and yes the coolant temp can be the problem. if it is plugged in, next time it won't start, unplug it and try again.
was very common on all honda's then. i really shoulda thought of that

what happens is the sensor range is wrong and when the engine is hot and the ecu thinks it's cold it floods on hot start.

E-AT_me · 10-21-2009, 02:46 AM

Quote:

Originally Posted by IHEARTMYHONDA91

no the car actully idles and runs just fine once its started...

i just need to figure out what the codes are for...

can i have the main relay checked at autozone or something?

no, autozone will not be able to test..

yeah, i think you're right about the coolant sensor. i just looked at the manual wrong.

IHEARTMYHONDA91 · 10-21-2009, 09:02 AM

so where is this coolant sensor?

if i disconnect the positive off the battery and let it sit for couple minutes, it will fire back up!

im so confused! haha

so is it the main relay or coolant sensor?

DEIVIONCRX · 10-21-2009, 10:48 AM

The coolant sensor for the ECU is on the side of the head, under the distrubitor.

Its the 2 wire connector, not the single wire bullet(thats the temp gauge).

IHEARTMYHONDA91 · 10-21-2009, 10:53 AM

so are you guys telling me that i can disconnect the sensor and i shouldnt have this problem anymore? well as far as starting it goes?

i would imagine that my temp gauge will not work now...

IHEARTMYHONDA91 · 10-22-2009, 09:21 AM

Ok so it is in fact the coolant temp sensor!

I unplugged it and the car fires up every time!

Now my question is... can I run my car without this sensor plugged in until I can find a working one?

E-AT_me · 10-22-2009, 09:31 AM

it will mess with your fuel mixture, but it should run fine.

DEIVIONCRX · 10-22-2009, 10:52 AM

The ECU will not have any idea what the engine temperature is. So in the recent future i would get a good Temp Sensor and replace it.

IHEARTMYHONDA91 · 10-22-2009, 12:25 PM

Quote:

Originally Posted by DEIVIONCRX

The ECU will not have any idea what the engine temperature is. So in the recent future i would get a good Temp Sensor and replace it.

My temperature guage works still...

Im wondering if that sensor is purposely for that hot starts issue?

DEIVIONCRX · 10-22-2009, 01:02 PM

No sir, there are 3 Water sensors.

One that turns on and off the Radiator fan.
One that runs the Temp Gauge on the Gauge Cluster.
One that tells the Computer how hot/cold the motor is.

Right now your car is running in limp mode, basicly full rich, it thinks the motor is full cold, like dead of winter the entire time, so your idle should be higher, and your MPG will severly decrease.

The hot start issue was because that sensor is dead. It was tricking it into thinking it was a different temperature than it really was, not allowing to add the right amount of fuel, when its hot.

night · 10-22-2009, 01:27 PM

Quote:

Originally Posted by IHEARTMYHONDA91

Ok so it is in fact the coolant temp sensor!

I unplugged it and the car fires up every time!

Now my question is... can I run my car without this sensor plugged in until I can find a working one?

you can hit up a junkyard can grab any temp sensor off an 80's fuel injected car. later than that the harness plug types changed and i can't promise it will plug in.

IHEARTMYHONDA91 · 10-23-2009, 10:10 AM

well the car isnt idleing any higher than normal and there is a half tank of gas in it now so i'll see how fast i burn that up!

and the car is not in limp mode! it runs fine!

10-20-2009, 09:23 AM	#2
night Junior Member Join Date: Oct 2002 Location: houston Posts: 761	Re: '87 Civic SI (MAIN RELAY?) fuel injected = main relay stick your head under the dash, upside down, and with a small flashlight look way up to the left behind the fuse box. you see an ~3x2" block with an 8P plug. next time it doesnt start tap on that with a screw driver while you turn it over. __________________ '85 Lude

10-20-2009, 11:24 AM	#3
E-AT_me Member Join Date: Sep 2001 Location: Strasburg, VA, USA Posts: 3,445	Re: '87 Civic SI (MAIN RELAY?) if it is the main relay, when you turn the key to position "two" you will not be able to hear the fuel pump prime.. this does not throw a code so it won't be what's wrong with the check engine light, or PGM FI light.. you have to pull that code from under the passenger seat. there are 4 LED's and depending on which ones are lit is the code #. __________________ 1986 civic Si.. B16a is in.. now to finish it.. Daily driver: 1991 Civic Si. 100 miles a day, 35mpg. track toy project: 1988 Civic sedan, d16a6 swap

10-20-2009, 11:42 AM	#4
IHEARTMYHONDA91 Junior Member Join Date: Oct 2006 Location: Bremerton, Wa, USA Posts: 224	Re: '87 Civic SI (MAIN RELAY?) ok well I checked the ecu and 2 lights are on constantly... 4 and 2 what is it?

10-20-2009, 04:53 PM	#5
E-AT_me Member Join Date: Sep 2001 Location: Strasburg, VA, USA Posts: 3,445	Re: '87 Civic SI (MAIN RELAY?) you know, i really wish i could post the website that has a service manual on this web board, but they block it.. so i will tell you the code is for a "TW Sensor" issue.. let me guess, when you get the car running, it has a high idle speed? it's your intake temp sensor.. __________________ 1986 civic Si.. B16a is in.. now to finish it.. Daily driver: 1991 Civic Si. 100 miles a day, 35mpg. track toy project: 1988 Civic sedan, d16a6 swap

10-20-2009, 10:44 PM	#7
night Junior Member Join Date: Oct 2002 Location: houston Posts: 761	Re: '87 Civic SI (MAIN RELAY?) are you sure you are reading that code right? 2 and 4 is the middle 2 lights, it is binary. and i'm showing that as the coolant temp. i'm assuming EAT just typed the wrong thing or he read positionally 2 and 4. and yes the coolant temp can be the problem. if it is plugged in, next time it won't start, unplug it and try again. was very common on all honda's then. i really shoulda thought of that what happens is the sensor range is wrong and when the engine is hot and the ecu thinks it's cold it floods on hot start. __________________ '85 Lude

10-21-2009, 09:02 AM	#9
IHEARTMYHONDA91 Junior Member Join Date: Oct 2006 Location: Bremerton, Wa, USA Posts: 224	Re: '87 Civic SI (MAIN RELAY?) so where is this coolant sensor? if i disconnect the positive off the battery and let it sit for couple minutes, it will fire back up! im so confused! haha so is it the main relay or coolant sensor?

10-21-2009, 10:48 AM	#10
DEIVIONCRX Junior Member Join Date: Jul 2005 Location: Oklahoma, Oklahoma, Usa Posts: 654	Re: '87 Civic SI (MAIN RELAY?) The coolant sensor for the ECU is on the side of the head, under the distrubitor. Its the 2 wire connector, not the single wire bullet(thats the temp gauge).

10-21-2009, 10:53 AM	#11
IHEARTMYHONDA91 Junior Member Join Date: Oct 2006 Location: Bremerton, Wa, USA Posts: 224	Re: '87 Civic SI (MAIN RELAY?) so are you guys telling me that i can disconnect the sensor and i shouldnt have this problem anymore? well as far as starting it goes? i would imagine that my temp gauge will not work now...

10-22-2009, 09:21 AM	#12
IHEARTMYHONDA91 Junior Member Join Date: Oct 2006 Location: Bremerton, Wa, USA Posts: 224	Re: '87 Civic SI (MAIN RELAY?) Ok so it is in fact the coolant temp sensor! I unplugged it and the car fires up every time! Now my question is... can I run my car without this sensor plugged in until I can find a working one?

10-22-2009, 09:31 AM	#13
E-AT_me Member Join Date: Sep 2001 Location: Strasburg, VA, USA Posts: 3,445	Re: '87 Civic SI (MAIN RELAY?) it will mess with your fuel mixture, but it should run fine. __________________ 1986 civic Si.. B16a is in.. now to finish it.. Daily driver: 1991 Civic Si. 100 miles a day, 35mpg. track toy project: 1988 Civic sedan, d16a6 swap

10-22-2009, 10:52 AM	#14
DEIVIONCRX Junior Member Join Date: Jul 2005 Location: Oklahoma, Oklahoma, Usa Posts: 654	Re: '87 Civic SI (MAIN RELAY?) The ECU will not have any idea what the engine temperature is. So in the recent future i would get a good Temp Sensor and replace it.

10-22-2009, 01:02 PM	#16
DEIVIONCRX Junior Member Join Date: Jul 2005 Location: Oklahoma, Oklahoma, Usa Posts: 654	Re: '87 Civic SI (MAIN RELAY?) No sir, there are 3 Water sensors. One that turns on and off the Radiator fan. One that runs the Temp Gauge on the Gauge Cluster. One that tells the Computer how hot/cold the motor is. Right now your car is running in limp mode, basicly full rich, it thinks the motor is full cold, like dead of winter the entire time, so your idle should be higher, and your MPG will severly decrease. The hot start issue was because that sensor is dead. It was tricking it into thinking it was a different temperature than it really was, not allowing to add the right amount of fuel, when its hot.

10-23-2009, 10:10 AM	#18
IHEARTMYHONDA91 Junior Member Join Date: Oct 2006 Location: Bremerton, Wa, USA Posts: 224	Re: '87 Civic SI (MAIN RELAY?) well the car isnt idleing any higher than normal and there is a half tank of gas in it now so i'll see how fast i burn that up! and the car is not in limp mode! it runs fine!

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