1987 Honda CRX bad gas mileage

1987 HONDA CRX
108,542 MILES • 4 CYL • FWD • MANUAL
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ILOVEHONDAS
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hi i own a 1987 honda CRX-si. i put a K&N cold air kit on it and it ran awesome. it got like 41 mpg. then i decided to put some plugs and wires on it. Long story short a spark plug got cross threaded in it and i ended up taking the head off it and having it milled and the hole re-tapped. i put it all back together along with a header ( and same o2 sensor). it started right up and runs great. but it sometimes studders going 50 in top gear but smoothes out at 55. then sometimes the PGM-FI (programmed feul injection) light comes on (when it studders). The PGM-FI light stays on until i shut the car off. i am guessing this has something to do with my bad gas mileage which has dropped to about 24 mpg. why is my gas mileage so bad?
Oct 23, 2008 at 3:54 PM
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KHLOW2008
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Hi ilovehondas,

With ignition switch turned, check the LED on the ECM. If it is 4 LED type, it is in binary and the code should 1 + 2 + 4 + 8 ( From RIGHT to LEFT) Let me know what you see.

If it is single LED, count the flashes.
Nov 23, 2008 at 8:20 AM
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ILOVEHONDAS
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when i turn on the key the only thing that lights up is the pgm-fi until the feul pump turns off. but no other light comes up i dont know if a 1987 honda would have that sort of code or if i have to to something else to get the code to flash? i dont know but no light flashes.
Dec 10, 2008 at 1:37 PM
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KHLOW2008
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Hi ilovehondas,

You have to locate the ECM. There is a small window for you to watch the light flashing on the ECM.

Unit should be found under passenger seat.
Dec 10, 2008 at 4:19 PM
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ILOVEHONDAS
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I found the ecm, and if youre looking from above the ecm on the floor under the passenger seat it would be the far left LED that lights up red, and it stays red even when started. I dont know if this is a code but i think that i read in my owners manual that it wont flash codes unless the pgm-fi light stays on. and my pgm-fi light only comes on under certain driving conditions (refer to first question to see what conditions) so let me know if the left red LED staying on while car is running is a code or if i should get the pgm-fi light to stay on then check for a code.
thanks!
Jan 21, 2009 at 7:52 PM
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KHLOW2008
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Hi,

If it has 4 LED, the far left = Code 8, ( Binary is used with 8, 4, 2, 1 accordingly).

This is a fault with the distributor assy.

No LED should be ON when vehicle is running.
Jan 22, 2009 at 3:12 PM
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ILOVEHONDAS
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So if the LED closest to the drivers side is lit up then it is in code 8? and this is something with the distributor? i was looking on the internet and i think that i also read that code 8 is the TDC sensor. or is that part of the distributor assembly? If so what would my next step be in fixing it? would it be the timing thats bad, or the distributor not working right. or someone said the oxygen sensor is bad. But i feel like i am getting closer to a solution to the problem and i appreciate your help and if i can get this fixed i will be more than happy to make a donation via mail or something. (i am 17 and dont have a credit card)
Feb 2, 2009 at 8:48 PM
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KHLOW2008
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Hi,

Yes, it is a problem with the Crank Angle sensor and it might cause difficulty starting/slow to fire up at times and the hesitation. You can do some test to confirm if the sensor is bad or it could be a broken wire or connection which could have occurred while doing repairs on the head.

At the distributor connector,disconnect and check the resistance between Orange/Blue and White/Blue terminals. Should be between 350 to 700 ohms. If withing specs, the distributor is ok and you need to check the wire continuity to the ECM. If both test ok, it could be the ECM that is faulty.

Regarding donations I am not sure how to go about doing it and would get the admins to let you know how.
Feb 3, 2009 at 8:38 AM
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THIS IS MIKE
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Feb 3, 2009 at 11:07 AM
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ILOVEHONDAS
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I used a Fluke DVOM and measured the resistance on the terminals from the connector both ways. I got 35.4k ohms from female end of connector to away from the distributor and i got, .701k ohms from male end of connector towards the distributor. Sometimes it was hard to get a reading on the male end of the connector it would be blank then flash O.L. about twice a second. i dont know if that was the DVOM sending a current through the wires and i just didnt have a good enough connection or what? is it ok to leave the battery connected for those tests? because i did. i think it is because otherwise i would have blown the fuse in the DVOM right?
Feb 6, 2009 at 4:28 PM
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KHLOW2008
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Hi,

It doesn't matter if the battry is connected or not because when the distributor coupler is disconnected, it would not be affected by the battery.

A reading of 0.701 k ohm is just out of specs, normally it should be about 0.500 k ohms

How many wires are there in the connector? The sensors are grouped into pairs, did you test other pairs?
Feb 7, 2009 at 5:48 AM
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ILOVEHONDAS
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there is four wires, so that would mean that there is two pairs of wires to check, i think. i checked the other two, (Pink/white wires) the male side of connector and got .700k ohms and on the female side (white/orange) and got 35.00 k ohms but again it was sometimes difficult to get a reading from the male side of the connector where as the female side would bring up a reading right away. what would cause the high resistance?
Feb 8, 2009 at 8:40 PM
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KHLOW2008
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High resistance could be due to contamination of the terminals pins. Check if there are any coatings of oxidation etc, which would cause bad conductivity and the CEL to show. Try some carb cleaner on the terminals and if possible use fine sandpaper to sand them down.
Feb 9, 2009 at 6:29 AM
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ILOVEHONDAS
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Could the high resistance also be from any corrosion in the distributor? because i remember when i took off the cover on the distributor some corrosion. could high resistance make the LED show up and could high resistance be the reason for my car acting up? or is it something else?
Feb 11, 2009 at 3:28 PM
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KHLOW2008
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When high resistance in the circuit is detected by the the ECU, it wuld cause the LED to show and this would affect the performance of the engine.

Low resistance would be due to shorting, higt resistance are usualy due to bad contacts. Corrosion can possibly high resistance.
Feb 11, 2009 at 3:43 PM