DSMAddicted

Guys,
I am helping a friend resolve an issue with his car.

Here are some facts:

• '97 Civic LX Auto (D16Y7 non VTEC) - bone stock
• Turn on the car when cold, idles fine for the first minutes. Then it starts surging.
• Idle only surges while in Park. If you put in any gear (Drive, Reverse) it doesn't surge.
• Pulled P0505, it was the only code shown (before my "work")
• After my work (didn't clear the codes), the reader pulled two instances of P0505 as well as two new ones: P0113 and P1509.
  See actual picture below (sorry, blurry).

Before I give too much importance to the new codes that appeared after the work I did, I am reminding myself that they might have appeared while I had the sensors unplugged. To know for sure, I've cleared ALL the codes using the Matco OBD2 reader and will pull the codes again this week, to see what comes out after several miles of driving.

Steps I've taken so far:

• Pulled throttle body, cleaned
• Pulled IACV, cleaned (although not much dirt came out, it just seemed black inside, but I could see the carb/throttle cleaner pass freely from one hole to the other)
• Changed TB gasket (the old one was caked and cracked)

I searched and thought about pulling and cleaning/resetting the FITV, but further research revealed that this car was not equipped with a FITV.

I read in another thread that I found during search that there's a vacuum line from the manifold to the fuel rail that can cause this issue as well. Does that apply to the D16Y7 as well (I don't have access to the car atm)? Remember, this is the one with the airbox on top of the intake manifold, throttle body mounted in the middle of the IM runners.

What are your thoughts guys? What should I check next?

Thank you in advance for the help,

-Walter

DSMAddicted

TTT

beecee18

you will be in the market for new iacv

circuit failure is not open circuit,

I know you need to at least try a new one, I have that same scantool and I keep my hands from getting dirty diagnosing with it.
I cant see the photo but which of the circles (monitors) in the top left corner of the display are still blinking?

DSMAddicted

Hmmm... I can't tell either.

The good news are that the CEL came back last night while my friend was driving home from work, so I'll pull it soon and take a better picture with better light.

In the mean time, are there any other suggestions?

beecee18

honestly just drive brotha and let the codes rack up again, that is if they do and report back with a few photos of all the codes, freeze frame data of the IAT code, and a close up and description of those circles, whether they are blinking or not.
This information will net you a fix

beecee18

This is good also, simple question. after resetting the ECM.
Did or did not the MIL illuminate instantly, or did it take some drive cycles to illuminate. Im trying to determine how many trips it took to finally illuminate the light.

ex. putting the key in and taking a drive for more then 15-20 min then removing the key consists constitutes 1 trip. Do you roughly remember how many trips passed before engine light illuminated again.

DSMAddicted

Sound good. I'll try to hook it up this afternoon and report back. Heck, I might just post a video.
How do I provide you with the IAT code freeze frame data?

I just asked my friend, it took two individual trips.

DSMAddicted

Update: just borrowed my friend's "CEN-TECH engineering" code reader (cheap Harbor Freight one).

He needed his Matco one. I hope this one can read the codes anyways. I'll post an update tonight.

DSMAddicted

Ninja edit from cellphone: pulled one single code... P0505 again.

Whatever suggestion you guys have will be greatly appreciated.

beecee18

circuit failure is failure of the part, I wouldnt drop coin on it yet although I would use a known good peice for testing purposes. maybe let a bud swap it real quick for test.
I would also check continuity from ECU to the connector clip of the IACV to make sure no break in the wire. But circuit failure=part failure

DSMAddicted

Thanks bud.
So I just look for a diagram, find the right pin on one of the ECU plugs and check continuity?

I'll start looking for a spare IACV in parallel as well.

beecee18

Yes, one end of the tools leads to the plug under the hood going to the IACV, and the other to the corresponding pin location at the ecu, you can find the Pinouts with a quick search. The tool should then zero out showing no resistance, a minute amount is ok, but my tool usually zeros out, do this with key off.
That matco scanner will take a quick snapshot of perimeters when the P0505 fault was detected and illuminated the MIL.
When viewing the single code, you would then press the FF button,
It will then display what the PID's were right when the MIL illuminated.
These PID's would include engine temp, o2 voltage, engine speed(rpm) and a $#!T-ton more. This freeze frame data help guys like us help determine the problems with out busting out wrenches most of the time STFT, and LTFT will be your most valuable asset as these are the fuel trims per bank of cylinders and let's the tech know why and how much fuel the ECU is adding or subtracting. Great for finding vacuum leaks ect.
The little circles up top are your monitors, if they are blinking they have not passed and a check engine light is in your near future. That's why I asked if the MIL illuminated directly after resetting the ECU. OBD2 has a few continuous monitors that constantly run, So if you had an open circuit(incorrect wiring, broken wire,ect.) the MIL illuminates instantly even after ecu reset. If MIL does not illuminate instantly the problem is NOT in the wiring, it is just a fault or descrepency with sensor activity ect.
Hope this helps.
Thank the tool for telling you to replace the part,
Not to just throw it at it.
Please understand OBD1 only monitors open circuits that's why it tough to troubleshoot without service manuals and electronic testing devices.
Make sence?

DSMAddicted

Indeed it does, buddy.
Are you a Honda technician btw?

Thanks again for the help.

beecee18

No im a finish carpenter,

Smog tech father

anything I have learned had nothing to do with honda

DSMAddicted

Got a replacement IACV this past weekend.

Before installing it, I am going to make sure there aren't any air pockets in the cooling system.
Going to plug my new radiator funnel, fill it with distilled water and hope for a few burps.

Will follow up accordingly.

Former User

If the problem persists after bleeding the cooling system, which seems likely, then set the idle speed to spec as describe in the service manual. There's a diagram in the FAQs sticky. Then go from there.

DSMAddicted

Thanks Ron.

Since the car got a new Head Gasket, water pump, timing belt, main seal etc. a couple of weeks ago (and the idle issue started since the work was performed), I strongly suspected there must have been air pockets in the system.

Yesterday I plugged the yellow funnel on the radiator, filled with distilled water and started the car. Overall the process took about 20 minutes. The radiator burped between 15-20 times and the water level in the funnel was almost an inch lower by the time I was done, so it seems like we did eliminate some air pockets. Idle is still surging, though.

It seems like the surging idle starts after the thermostat opens. I'll go ahead and try setting the idle like you suggested. I just printed out this diagram from the FAQ but I don't see any mention of surging idle on the diagram. I did notice it mentions to check idle between steps, but how am I supposed to check idle when it surges from 1k to 2k repeatedly?

Should I try following the diagram and messing with the idle screw even with this surge issue? Furthermore, should I clear the P0505 code before attempting idle adjustment to factory spec?

If the idle continues to fluctuate, I suppose I ought to proceed with IACV swap.

Thank you.

Former User

Start here:

-Warm up the engine until the idle speed starts to fluctuate, and then remove the air intake system to allow access to the top of the throttle body (TB).

-Inside the large opening of the TB, you'll see a hole or port that bypasses air through the IACV. If you cover this hole with your finger, does the idle speed drop and the fluctuation stop?

Depending on the outcome, then proceed to these:

Sure, just see if the same code repeats afterwards.

Follow the diagram to the tee. You need an accurate external tach or scan tool that measures engine rpm for the procedure.


No. Don't replace parts at random. There are more tests to be done.

mann-nyc

Just solved a problem like this i just had. cleaned the iac 3 times still ni fix. Changed the iac and boom idle was normal.

DSMAddicted

Thanks Ron.
So to make sure I get this right: you want me to proceed with the above only if the idle smooths out by covering the IACV opening inside the TB, right?

So in other words:

• if I cover the IACV opening in the TB and idle stops fluctuating, THEN keep it covered (temporary masking tape or whatever) and proceed with adjusting idle like in the diagram (and yes, using scan tool to monitor rpm)?
• if I cover the IACV opening and idle continues to fluctuate, stop and report back on here for further testing instructions?

Thanks for sharing man. Hopefully we'll fix mine soon too.
If it comes to swapping IACV, I have one ready.

DSMAddicted

UPDATE (for documentation purposes):

Due to scheduling issues and the urgency of getting the car emission tested and taken care of, we tried installing the 'new' IACV.
Issue resolved, car runs great.

Thank you for the help, everyone.
I hope this thread (and the troubleshooting steps on it) will help someone else in the future.