IHEARTMYHONDA91

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?

night

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

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

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

what is it?

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..

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?

night

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

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

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

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

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

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

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

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.

IHEARTMYHONDA91

My temperature guage works still...

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

DEIVIONCRX

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

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

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!