1998 Accord low idle problem after new Idle Air Control valve

[JeffKeryk]

1998 Accord LX 2.4L 4 banger, 165K ODO. Started with idle surge and P0505 trouble code.
I installed the IAC (Idle Air Control) valve (cleaned TB, plenum and butterfly) which fixed the surge, but now the idle is like 300 RPM and dies. I tried the reset (battery terminal off 10 min, start and hold 3000 rpm for 5 minutes) but after letting off throttle it drops back and dies.

What was funny was, I did not reinstall the valve cover tube that inserts into air cleaner intake tube; when I did the idle dropped. I also cleaned the PCV valve.

I will check it over again tomorrow. Any guidance is appreciated.

 

[fsdork]

Is the IAC a Honda-branded part or made by the OEM supplier? After the IAC on our '03 Explorer packed it in, I went through a couple of NAPA replacements which didn't work right off the bat. I took the second one back and bought the Ford part - that one worked like a charm.

 

[JeffKeryk]

Is the IAC a Honda-branded part or made by the OEM supplier? After the IAC on our '03 Explorer packed it in, I went through a couple of NAPA replacements which didn't work right off the bat. I took the second one back and bought the Ford part - that one worked like a charm.

Not from Honda. It's branded Honda, but I know it is from who-knows-where. But the surge is gone, so that's a good thing.

 

[Nukeman7]

Not from Honda. It's branded Honda, but I know it is from who-knows-where. But the surge is gone, so that's a good thing.

As I indicated in the original thread, anything other than an authentic Honda OEM IAC will likely not communicate correctly with the PCM. If you did not buy the new IAC from a legitimate Honda dealership (e.g., eBay, Amazon), it is likely counterfeit.

I highly recommend thoroughly cleaning the carbon gunk out of the original Honda IAC with carb cleaner and a pick, lubricating the bearings with light oil, then reinstalling it.

 

[mk378]

Check the air passages leading to the IACV. They may be clogged.

Make sure all the connectors around the TB are plugged to the correct device. Hondas are not "idiot proof" like American cars.

If it is stalling, open the idle screw at the top of the throttle body.

If coolant level is low there will be idle surge.

Any codes thrown now?

 

[JeffKeryk]

I cleaned the original IAC, cleaned the TB passages and reinstalled it. Ran poorly.
That's why I bought the Amazon part, which has to be counterfeit.

There is no surge or trouble codes, just low idle. I will mess with it more tomorrow.

I will try @mk378 idle screw suggestion.
I appreciate all your help!

 

[PandaBear]

Did you check if your MAF sensor is clean? or PCV valve? or bad wiring?

 

[Nukeman7]

I cleaned the original IAC, cleaned the TB passages and reinstalled it. Ran poorly.
That's why I bought the Amazon part, which has to be counterfeit.

Did you separate the black motor assembly from the original IAC before cleaning it? If not, the IAC is probably not fully clean and the shutter valve is probably still sticking a bit. In order to remove the motor, you must take out both of the silver screws shown in the photo below with a special 5-point Torx bit. Once the motor is removed, you will be able to rotate the IAC's shutter axle rod & magnet to feel where it is binding.

There is no surge or trouble codes, just low idle. I will mess with it more tomorrow.

I will try @mk378 idle screw suggestion.
I appreciate all your help!

For the record, Honda forums (and most mechanics specializing in Honda vehicles) highly discourage adjusting the idle air screw on the throttle body since that is almost never the source of a poor idle problem. Most TB idle air screws are sealed at the factory with paint or surface thread sealant to discourage tampering. Adjusting this screw will only serve to mask the real problem, not resolve it.

 

[ATex7239]

Not the same engine, but we had a low idle surging/stalling issue on the Hyundai and new plugs and coil packs cleared it right up.

 

[JeffKeryk]

I was confident the engine had spark, compression and gas, so I figured the low idle/die condition was lack of air. I jammed a screwdriver in the throttle cable lever to open the butterfly just a taste. Fired right up.

I tightened the 2 accel cables to remove slack; I had loosened them to pull the throttle body. Engine idles barely, but was clearly not right. I let it warm up, and gave it a little gas to test. Engine died. Threw a P0304; a cylinder 4 misfire. Pulled all the plugs, fouled badly. Uber rich. OEM NGKs have 6K. The internals are not worn, at least badly. I know this car. Will swap out plugs tomorrow and see what happens. Note, this car sat for almost 6 months. With a little (or a lot) luck this has to do with a faulty IAC valve. It did not throw a P0505 and the idle did not surge.

As always, I would appreciate your thoughts... Thank you.

 

[Nukeman7]

Those NGK plugs look terrible for only 6K miles on them. It's either burning oil or running extremely rich. While this theory may seem out of the box, I would take out the fuel pump (easily accessible from the trunk) and pump out all of the old gas. While 6 months is not that long, I experienced gas going bad in a pristine 1999 Honda Accord after ~1 year stored in a climate controlled garage. I'd put 10 gallons of non-ethanol gas and a bottle of Redline SL1 fuel system cleaner in the tank and take it out for an "Italian Tune-Up" to flush out the injectors.

 

[JeffKeryk]

Those NGK plugs look terrible for only 6K miles on them. It's either burning oil or running extremely rich. While this theory may seem out of the box, I would take out the fuel pump (easily accessible from the trunk) and pump out all of the old gas. While 6 months is not that long, I experienced gas going bad in a pristine 1999 Honda Accord after ~1 year stored in a climate controlled garage. I'd put 10 gallons of non-ethanol gas and a bottle of Redline SL1 fuel system cleaner in the tank and take it out for an "Italian Tune-Up" to flush out the injectors.

It is not burning oil; the last set of NGKs looked fine. It is pig rich; #1 plug was wet. I appreciate your thoughts. I will take this one step at a time. It is possible I get another car...

 

[Oliveoil2]

Really rich.