Idle Problem: '99 Civic EX
12-01-2016
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Idle Problem: '99 Civic EX
Hey Civic Forums!
I own a 1999 Honda Civic EX. D16Y8 Automatic. The engine light has been going on and off with the same code for the Idle Air Control. The car had high idle when I started it up. The Idle would also go between 1500 to 1700 rpm while Idling. Then the car started dropping rpm while driving. For example, driving ~35mph @ 3000 rpm, the rpm drops down to 1500, back up to 2500, down to 1500, back to normal driving. It happens after the engine is sufficiently warmed up and I am basically coasting at one speed. The car feels as if it is about to stall out then comes back to life. I suppose it might not be exactly an idle issue because its happening under load. Engine light code is P0505: Idle air control system. This is what has been done so far:
- Checked made sure there is no air in the cooling system
- Smoke tested the engine, no vacuum leaks.
- Cleaned and checked throttle body
- Replaced gaskets on IACV and TB
- Voltage tested all the sensors, all good.
- Checked PCV valve, working properly and cleaned.
- Timing Belts and Water Pump working properly
- Tried Resetting base idle, didn't help
- No problems with fuel lines
- Replaced IACV, still having same issue.
It honestly doesn't seem like anything mechanical. Probably going to buy a used ECM and install that because that is what multiple mechanic friends of mine have recommended. If that doesn't help, which i'm hoping it does, where should I go next? Clean the EGR? Could a clogged cat have any effect?
Thanks for your help!
I own a 1999 Honda Civic EX. D16Y8 Automatic. The engine light has been going on and off with the same code for the Idle Air Control. The car had high idle when I started it up. The Idle would also go between 1500 to 1700 rpm while Idling. Then the car started dropping rpm while driving. For example, driving ~35mph @ 3000 rpm, the rpm drops down to 1500, back up to 2500, down to 1500, back to normal driving. It happens after the engine is sufficiently warmed up and I am basically coasting at one speed. The car feels as if it is about to stall out then comes back to life. I suppose it might not be exactly an idle issue because its happening under load. Engine light code is P0505: Idle air control system. This is what has been done so far:
- Checked made sure there is no air in the cooling system
- Smoke tested the engine, no vacuum leaks.
- Cleaned and checked throttle body
- Replaced gaskets on IACV and TB
- Voltage tested all the sensors, all good.
- Checked PCV valve, working properly and cleaned.
- Timing Belts and Water Pump working properly
- Tried Resetting base idle, didn't help
- No problems with fuel lines
- Replaced IACV, still having same issue.
It honestly doesn't seem like anything mechanical. Probably going to buy a used ECM and install that because that is what multiple mechanic friends of mine have recommended. If that doesn't help, which i'm hoping it does, where should I go next? Clean the EGR? Could a clogged cat have any effect?
Thanks for your help!
Last edited by agb22; 12-01-2016 at 10:10 AM.
12-02-2016
#2
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Re: Idle Problem: '99 Civic EX
Sounds like you may have read this thread: http://honda-tech.com/forums/honda-c...2127246/page2/ looking for answers. Check out reply #42 in that thread. Dude replaced spark plug wires and the issue went away so, a possibility but, you don't want to throw parts at it without testing. Ohms test and spark test spark plug wires first. If, you have a friend with the same engine ask them if you can swap wires for testing.
Ohms test ECT at operating temp. ECT sensor 200-400 Ohms = spec. Read all of this: http://honda-tech.com/forums/honda-c...found-3262136/ Ron J. is the Ezone of HT.
May or may not be related to the idle surge but, the following is a quick easy test: Try a power balance (drop) test. Can do it when car is idling and pull each fuel injector lead off one at a time and listen for engine to drop in idle (near) the same amount cylinder to cylinder. If any of the cylinders doesn't drop in idle when the injector lead is disconnected there is a compression or injector issue.
When was the last valve lash adjustment performed?
Ohms test ECT at operating temp. ECT sensor 200-400 Ohms = spec. Read all of this: http://honda-tech.com/forums/honda-c...found-3262136/ Ron J. is the Ezone of HT.
May or may not be related to the idle surge but, the following is a quick easy test: Try a power balance (drop) test. Can do it when car is idling and pull each fuel injector lead off one at a time and listen for engine to drop in idle (near) the same amount cylinder to cylinder. If any of the cylinders doesn't drop in idle when the injector lead is disconnected there is a compression or injector issue.
When was the last valve lash adjustment performed?
Last edited by Wankenstein; 12-02-2016 at 10:35 PM.
12-05-2016
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Sounds like you may have read this thread: http://honda-tech.com/forums/honda-c...2127246/page2/ looking for answers. Check out reply #42 in that thread. Dude replaced spark plug wires and the issue went away so, a possibility but, you don't want to throw parts at it without testing. Ohms test and spark test spark plug wires first. If, you have a friend with the same engine ask them if you can swap wires for testing.
Ohms test ECT at operating temp. ECT sensor 200-400 Ohms = spec. Read all of this: http://honda-tech.com/forums/honda-c...found-3262136/ Ron J. is the Ezone of HT.
May or may not be related to the idle surge but, the following is a quick easy test: Try a power balance (drop) test. Can do it when car is idling and pull each fuel injector lead off one at a time and listen for engine to drop in idle (near) the same amount cylinder to cylinder. If any of the cylinders doesn't drop in idle when the injector lead is disconnected there is a compression or injector issue.
When was the last valve lash adjustment performed?
Ohms test ECT at operating temp. ECT sensor 200-400 Ohms = spec. Read all of this: http://honda-tech.com/forums/honda-c...found-3262136/ Ron J. is the Ezone of HT.
May or may not be related to the idle surge but, the following is a quick easy test: Try a power balance (drop) test. Can do it when car is idling and pull each fuel injector lead off one at a time and listen for engine to drop in idle (near) the same amount cylinder to cylinder. If any of the cylinders doesn't drop in idle when the injector lead is disconnected there is a compression or injector issue.
When was the last valve lash adjustment performed?
01-26-2017
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Re: Idle Problem: '99 Civic EX
I had the SAME exact issue with my 2000 Civic VP. I was pulling my hair out trying to make the %#@$'n P0505 go away. I have read horror stories about people spending TONS of money trying to fix this. It turned out to be the stupid PCV valve. Only use a Honda one. I also noticed when installing it there was a bend in the two inch piece of tubing that comes off the PCV. If not installed the way it was, the PCV will not seat properly and result in a tiny vacuum leak and can throw the dreaded P0505. It is a freakin bitch to get your hands up there to get the correct angle. What I did to fix was put a bead of silicone at the base of the PCV where it goes into that black box. I think the civic is really sensitive to vacuum leak and the slightest leak will throw the P0505. This fixed it and the P0505 has not come back. Try this fix, it is inexpensive and can potentially fix your problem.
