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Intermittent Idle Issue

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Intermittent Idle Issue

Postby CIVICFORLIFE » Thu Sep 22, 2016 5:40 pm

Have a 1988 Civic LX. After car warms up I will get an occasional low idle bobble issue. Will be sitting at a traffic light and the idle will start bouncing between 500 and 750 rpms. The engine then corrects the issue back to normal idle, but it can reappear. Sometimes having the AC on will aggravate the problem. The kicker is it doesn't do it all the time. I can get to the next traffic light and have no issue even with the A/C on. Have changed oxygen sensor....temperature sensor (which was bad)...have cleaned the idle air control valve screen....have adjusted the timing after mechanic changed distributor and didn't align it properly. Plugs are new too. Car has no problems starting and idle doesn't surge either. Car runs fantastic...other than this problem. Is it worth trying to remove idle air control valve and soak it good? Any ideas would be greatly appreciated. I am NOT a mechanic, but do have a good one. He's running out of ideas. Also no codes are being generated either. Thanks!
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Re: Intermittent Idle Issue

Postby Sandman » Thu Sep 22, 2016 8:40 pm

I would probably get a fuel pressure gauge and see if the pressure is dropping while that happens. One thing that it could be is a dying fuel pump.
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Re: Intermittent Idle Issue

Postby CIVICFORLIFE » Fri Sep 23, 2016 8:58 pm

I will check it out and report back. I don't have any starting issues or hesitation/acceleration issues....this issue only happens when car is warmed up.
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Re: Intermittent Idle Issue

Postby 91hatchligon » Sat Sep 24, 2016 6:21 am

I had this problem it turned out to be a vacuum leak.
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Re: Intermittent Idle Issue

Postby CIVICFORLIFE » Tue Nov 22, 2016 11:16 pm

OK...here is the 11/22/16 update. This problem is much harder to diagnose in the cooler Northeast weather as the car will cough less. Changed the IAT sensor which looked pretty burnt and thought I had found the issue as it was OK for two days....then back we go again. Mechanic said it would probably throw a code eventually but it is difficult to diagnose when I can't guarantee the car will "cough" on any given day or in any given situation.

The mechanic then suggested that sometimes the computer can get stupid. He told me to remove the negative cable on the battery overnight and then reattach in the morning and drive the car around for 15 minutes so the computer can relearn....essentially rebooting the computer. I'm now on my third day of driving with no temporary cough. I will report back after another week or if the car does coughs again in the interim...so far so good.
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Re: Intermittent Idle Issue

Postby Sandman » Mon Nov 28, 2016 11:07 pm

CIVICFORLIFE wrote:The mechanic then suggested that sometimes the computer can get stupid. He told me to remove the negative cable on the battery overnight and then reattach in the morning and drive the car around for 15 minutes so the computer can relearn....essentially rebooting the computer. I'm now on my third day of driving with no temporary cough. I will report back after another week or if the car does coughs again in the interim...so far so good.

Sorry for the later reply. Late nights working on the sedan.
The ECU in these doesn't work that way. All that does is reset error codes. The ECU works on sensors and charts, nothing to be learned here. The sensors it operates on give out cold hard data. They can malfunction, but then you'd have an error code.

Make sure you've cleaned your EACV/IACV, make sure your timing is good, do a service on the engine(all the filters, plugs, liquids etc.) and see what that does.

MOST of the idle issues in these are caused by the EACV/IACV(name dependent on source and model). The rest are up to manintanance issues and timing(be that ign or engine timing). When all of the above have been checked and still it's acting up - better call the ghostbusters.
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Re: Intermittent Idle Issue

Postby CIVICFORLIFE » Sat Jan 07, 2017 7:57 pm

Thanks Sandman for your input. Here is the 1/7/17 update. Thought I was out of the woods with the "reboot" of the ECU. Went 4 weeks without an issue and then it bobbled temporarily at a stop light and recovered. Went another 2 weeks without an issue.....and then we had a 55 degree warm surprise day as it's been very cold. I went about 2 miles for an errand and then it started again. Seemed like every stop that day and on every turn taken the idle would bobble and recover. Thought for sure a code would be thrown or finally I could have the engine looked at while it was doing the bobble. The next day and the past week...no issues. The cold weather definitely affects whatever is wrong. At this point instead of changing more parts blindly, I'm going to wait until the spring when it warms up as I suspect it's going to be a lot worse. For the record...the IAC screen was cleaned...coolant sensor/oxygen sensor/Intake air sensor and plugs were all changed and distributor was replaced and timing double checked. The car exhibits NO other problems...just the random bobble between 0 and 1000 RPM's ONLY at idle and more importantly... at a time and place of its' choosing...you can't at this point make the car behave this way for a mechanic....it will purr like a kitten at idle when you take it in.
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Re: Intermittent Idle Issue

Postby CIVICFORLIFE » Fri Mar 31, 2017 9:03 pm

OK boys here's the 3/22/17 update on the mystery idle issue. I was getting antsy for spring and we finally had a 50 degree day so I tried an experiment. I got the car to go into it's bobbling mode after warming up for 10 minutes. As usual it would bobble for a little bit and then correct. I unplugged the idle air control valve and the car then goes into base idle of around 500 rpm. Left it there for 15 minutes without incident....purrs like a kitten. So I figured it's either the idle air control valve or what my mechanic figures....some sensor sending some info to the computer and then the computer telling the valve to close off. I got a refurb of the exact same idle air control valve and decided to install it...am not a mechanic but it wasn't too bad. Had another warm day yesterday and decided to idle it for a while. No luck...car went into it's bobble mode so it is NOT the idle air control valve. And also there is no screen on the 1988 version of that part. It is probably 25 degrees out today and had the car out for 4 or 5 stops.....no issues.....If it was 50 degrees out the car DEFINITELY would have done its' bobble thing.

So to recap here's what's been changed:
Distributor (which was bad originally)
Timing was checked
Spark plugs AND wires
O2 sensor
Coolant Sensor
Intake air Sensor
Idle Air Control Valve

Not sure if the Map or TPS sensor would cause my problem. Of course no codes ever thrown! The car did have a burnt valve before all of this started for which the head was pulled and serviced. I'm wondering if something was put back wrong or maybe a bad gasket somewhere. Other than this issue the car runs perfectly! Definitely seems that ambient air temperature lessens the chance of this condition as again I had the car out 4 or 5 times today (very cold out) and the coolant temp was definitely warm and of course no issues whatsoever!
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Re: Intermittent Idle Issue

Postby bsabc » Tue Apr 04, 2017 6:39 am

Did not see if your lx is dual point or multi point. My dx 1.5 had the same problem when spring came and it was solved by replacing the intake complete with the tps . Found out that the tps on the dual point is factory set and not avalible seprate in canada. Stopped the up and down idle issuse. they are cheap at the wreckers here so might be a way to go. hope that can help as parts are getting hard to get for the 1.5 dx dual point
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Re: Intermittent Idle Issue

Postby CIVICFORLIFE » Wed Apr 05, 2017 9:29 pm

I have the dual point not the multi point. I just noticed in a Honda Tech Forum that way back in 1991 there was a service bulletin No. 91-031 issued that says " The engine may occasionally idle roughly or erratically after coming to a stop with the throttle fully-closed." and the cause listed is "Inadequate grounding of the throttle angle sensor circuit." I'm wondering if that is my problem and was thinking of taking it into a dealer. Flate rate time was .3 hours to fix.
Not sure if I mentioned before but when it's a humid rainy day it REALLY gets bad. And if the next day is cold and dry there's no issue....like something starts getting shorted out.
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