Intermittent idle issue: '88 Civic

JRCIVICFORLIFE

New Member
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!
 

Ravendragonslair78

Respected
JRCIVICFORLIFE said:
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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I would try cleaning the IACV or go to a junkyard and find a IACV for cheep and see if that helps. Or your throttle positioning sensor might be going bad and have intermittent loss causing the bobble in idle.
 


JRCIVICFORLIFE

New Member
Thanks for the responses...car is at mechanic now. That picture is of the fast idle "screw." I did see a video of the tightening down of that white part with a flat blade screwdriver. My understanding is that this will correct hunting idle where the idle swings from low to high constantly. Am I correct in my understanding? I will mention this to mechanic anyway.
They have cleaned the screen of the IACV but have not removed it and given it a good soak. Also my understanding is the TPS rarely goes on these cars. I would think that if it was the TPS I would be experiencing other issues like acceleration. This problem ONLY occurs after the car is warmed up.
 


Ravendragonslair78

Respected
JRCIVICFORLIFE said:
Thanks for the responses...car is at mechanic now. That picture is of the fast idle "screw." I did see a video of the tightening down of that white part with a flat blade screwdriver. My understanding is that this will correct hunting idle where the idle swings from low to high constantly. Am I correct in my understanding? I will mention this to mechanic anyway.
They have cleaned the screen of the IACV but have not removed it and given it a good soak. Also my understanding is the TPS rarely goes on these cars. I would think that if it was the TPS I would be experiencing other issues like acceleration. This problem ONLY occurs after the car is warmed up.
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From what I have experienced in the past with a senser going bad is once it starts to get hot it will start to malfunction. If it is the TPS it would cause the car to either shut off when coming to idle or shutter at idle. But once you give it gas it will run and accelerate fine. I currently have two 91 civics, one is a dx and the other is a lx. The lx is the one I had to change the TPS on. But hopefully a good soak of the IACV will do the trick. Keep me posted, I'm interested to know what it is causing the problem.
 

MACE

New Member
yeah me too.
my idel surges ometimes as well, but stops when it gets warm
check your coolant level and blled the coolant system mine does it bad when its low on coolant
 

JRCIVICFORLIFE

New Member
MACE said:
yeah me too.
my idel surges ometimes as well, but stops when it gets warm
check your coolant level and blled the coolant system mine does it bad when its low on coolant
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That's sort of the opposite of what mine does. I have ZERO issues when it's cold or starting vehicle....in fact it takes longer for the problem to develop in cooler weather. My idle does NOT surge. It will "bobble" or "cough" like it is going to stall AFTER warmup....the idle will bobble between say 500 and 750 and then the computer will steady the rpm until it happens again and we go through the cycle again. It's either not getting enough air or too much gas temporarily. It's in the shop now.....

P.S. Coolant level is up to the top!
 

XpL0d3r

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JRCIVICFORLIFE said:
That's sort of the opposite of what mine does. I have ZERO issues when it's cold or starting vehicle....in fact it takes longer for the problem to develop in cooler weather. My idle does NOT surge. It will "bobble" or "cough" like it is going to stall AFTER warmup....the idle will bobble between say 500 and 750 and then the computer will steady the rpm until it happens again and we go through the cycle again. It's either not getting enough air or too much gas temporarily. It's in the shop now.....

P.S. Coolant level is up to the top!
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This could be o2 sensor related too. When the engine is cold, it wont use o2 sensor feedback to control A/F ratio. When it warms up it goes closed loop and starts to use o2 sensor feedback. I had a sort similar issue, where the motor ran fine when cold, but once warmed up, it had 0 power. I could floor it and it would go no where up until like 4k, then it would zip ahead like normal. o2 sensor was the cause, it was working enough to not throw a CEL but crappy enough to screw up the A/F ratio. May want to look into testing it if all else fails.
 

JRCIVICFORLIFE

New Member
Ravendragonslair78 said:
Unplug it while it's running and see if it makes a change in sound. If it doesn't then replace it.
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OK here's the 11/22/16 update. Changed the IAT sensor as it was cheap and easy to do. Sensor looked pretty burnt. I was lookin good for two days and then we're back to the occasional bobble. Again the computer corrects the issue immediately. Had a long talk with my mechanic....without changing a lot of parts this one is difficult because I can't guarantee when or if the idle will bobble. My mechanic said it will probably throw a code at some point. He then came up with an interesting idea. He told me to disconnect the negative battery cable overnight and reattach in the morning.....essentially rebooting the computer....then drive it around for 15 minutes so it can do its' relearning. So far it's been three days with no issues! I know I just jinxed myself. I will report back in a week or so or if the problem reappears. What a son of a gun if that's all it was....fingers are crossed. Not sure if any of you have solved any issues before by doing that.
 

Ravendragonslair78

Respected
JRCIVICFORLIFE said:
OK here's the 11/22/16 update. Changed the IAT sensor as it was cheap and easy to do. Sensor looked pretty burnt. I was lookin good for two days and then we're back to the occasional bobble. Again the computer corrects the issue immediately. Had a long talk with my mechanic....without changing a lot of parts this one is difficult because I can't guarantee when or if the idle will bobble. My mechanic said it will probably throw a code at some point. He then came up with an interesting idea. He told me to disconnect the negative battery cable overnight and reattach in the morning.....essentially rebooting the computer....then drive it around for 15 minutes so it can do its' relearning. So far it's been three days with no issues! I know I just jinxed myself. I will report back in a week or so or if the problem reappears. What a son of a gun if that's all it was....fingers are crossed. Not sure if any of you have solved any issues before by doing that.
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Yeah I have, after changing my dizzy do to the TDC thats built in to the dizzy. Car wouldn't run rite but once I disconnected the battery for an hour then reconnected it, the car ran like new. Glad to hear you got it fixed.
 

JRCIVICFORLIFE

New Member
Thanks in advance for everyone's help. 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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beth danskin

New Member
My Honda Civic 89 has the same darn problem exactly. I have also replaced the IAT sensor. I will try the battery trick tonight. Thank you so much for all your information.
 

JRCIVICFORLIFE

New Member
beth danskin said:
My Honda Civic 89 has the same darn problem exactly. I have also replaced the IAT sensor. I will try the battery trick tonight. Thank you so much for all your information.
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The battery trick did not work for me as I noted above...the issue came back. Let me know how you make out. I live in the Northeast and the cold definitely lessens the instances of the idle bobble. Is it cold where you are now and do you notice the same behavior? I'm pretty much on hold until it warms up in the spring as I can't make the car do what it does in front of a mechanic.
 
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