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91Civic LX idle

  #1  
Old 05-08-2009, 01:34 PM
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Default 91Civic LX idle

hello

we just bought a 91 civic - $300 - he-he. actually, runs quite well.
it is a MPFI engine.
someone rigged idle mechanically on the throttle by locking the throttle cable. when i had it all untangled, engine stalls. i figured that rpms can be set with an adjustment screw, so i did it for more or less decent rpm number and no stalling.
here's symptoms: engine starts and warms up by itself very well, so the idle control unit obviously works. then, rpms go down to about 800. after some driving, rpms crawl up into 1500 by themselves and have tendency to stay there.
i sprayed carb cleaner around throttle and everywhere close to it, no air is sucked in, as it did not influence rpms at all. i had everything outside throttle cleaned and sprayed cleaner into the throttle yesterday.
my question is: what can cause rpms to crawl up and stay there? i loosened throttle cable completely. cruise cable is loose. will it be idle speed control actuator? that mushroom looking thing with vacuum attached to it? as when i had that vacuum hose removed off it, engine went into some 3000 rpms right away. can it be removed and cleaned inside, like i did many EGR valves before?
appreciate suggestions. not much of a problem, but annoying, plus costs more gas.
 
  #2  
Old 05-08-2009, 01:56 PM
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Is the LED on the ECU blinking a trouble code? To know, pull the front passenger carpet back to see the ECU.
 
  #3  
Old 05-09-2009, 07:00 AM
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Hi RonJ

yes, it flashes 1, then 16. of course, i have googled all this right away, and found A MESS on code 16, including many of your previous posts.

appears, there are many suggestions. code says: fuel injector. people say - main relay. then they say - those injectors are rare to fail and basically need to be cleaned. which we have can of seafoam in the tank since thursday, except can't really drive the car as it is not tabbed, to run seafoam through injectors.

then, there's suggestions like fuel filter and fuel regulator. i could not find a single straight answer to what to do with 16. most say: bad soldering points on main relay, replace relay.

so, i am humbly open to a good suggestion. it is not running bad at all, so i do not believe it is injectors. i had engine to 6000 rpms in a click, so secondary injector works. it just has tendency to idle high on warm, so there's something causing this. otherwise, for age and 178000 poor maintenance miles, it does Honda well. kid will be driving this to college, which is 32 miles one way, so i do not want him to get caught on freeway.
thank you.
 
  #4  
Old 05-09-2009, 07:14 AM
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hey, Ron - i found this:
https://www.hondacivicforum.com/foru...vic+error+code

i think, can't do any better. i'll start with running those diagnostics. no, better off - with resetting the code.
in my humble opinion, either ecu is running idle too high, or idle actuator is sticky, or vacuum runs low on it on hot, thus it allows higher rpms.
but i am new to this engine, so i am most open to suggestions.
 
  #5  
Old 05-09-2009, 07:40 AM
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Do you have the 1.5 liter engine?
 
  #6  
Old 05-09-2009, 07:49 AM
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Self diagnosis and Code 1:

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  #7  
Old 05-09-2009, 07:50 AM
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Code 16: (Harbor Freight Tools sells a basic engine stethoscope for about $3.)

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  #8  
Old 05-10-2009, 07:33 AM
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thank you, Rob. i have stethoscope. it's all dandy, but what am i going to do about that specialty PGM-FI harness?

i guess, we do have 1.5 engine. one with big mushroom on top of throttle. sorry, i called it MPFI. it is dual point injection - throttle body with 2 injectors in it. my bad.

basically, it is O2 sensor. fine, no big deal. i'll just replace it.
also, i have attached layman's - but practical - way of dealing with code 16. MANY say it is main relay related. once again, Civic bunch is positive, it is main relay. gods have mercy over me getting it out. i have large hands, and it's hidden well. reasoning is: 16 is injector code. main relay runs injectors power. main relay is known to fail on soldering points on that year Civics. for 91 and 178K miles - no wonder.

i guess, attaching files does not work...

i hope, outside links are permissible:
http://www.tegger.com/hondafaq/mainrelay.html
http://www.marklamond.co.uk/tech-hon...main-relay.htm
http://www.tegger.com/hondafaq/mainrelayfix/index.html
 

Last edited by ukrkoz; 05-10-2009 at 07:47 AM.
  #9  
Old 05-10-2009, 10:25 AM
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A bad main relay will typically lead to a no-start or stall condition. I think you should troubleshoot code 16 as detailed in the diagrams.
 
  #10  
Old 05-11-2009, 05:44 AM
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actually, as of yesterday and after little driving with seafoam in gas and TLC i've done to it, the problem is, basically, non-existent.
engine runs well on my book. i'll bring my buddy in whilst replacing valve cover gasket, he'll adjust rocker tap. that's about it that needs to be done. we should tab it today or tomorrow and the rest of seafoam will go through the system.

thank you, Rob. oh, btw, CEL does not come up. never did. so, i am not quite worried about code 1.
 
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