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Merry Christmas,

Unfortunately, I’ve searched this forum without much avail. Idle issues seem to be common, although I am finding something to be amiss.

A month ago I took my throttle body apart (also cliché of my research), cleaned it, the IAC, and proceeded with the reinstall. I set out to fix a small surge in the idle, and the overall drivability of the vehicle. I succeeded, at first. The car ran great for about a week. Until, the engine started its campaign of high idling and complete resistance to repair.

Symptoms
1) Idling at 2000 RPM
2) CEL along the lines of "Manifold Barometric Pressure out of Range." I do not remember the specific numerical code, although I believe it was along the lines of P0106

Treatment
1) Throttle and Cruise control cables appear to be "free" and uninhibited.

2) Idle relearn procedure as outlined by the Haynes manual and the method outlined by gearbox on the forum. Unfortunately, this seemed to have no effect.

3) Search for vacuum leaks.
- I replaced the throttle body gasket.
- Pulled the vacuum line off the back of the throttle, the engine would idle higher. With my finger plugging the line, engine idling would settle back at 2000rpm.
- Positing my thumb over the IAC port would stall the engine.

4) Pursuit of the IAC
- I cleaned it, with no avail
- Pulling the ECM harness from the IAC causes the engine to idle higher
- I swapped the IAC with no change in results.

5) Burp the cooling system
- While little air seemed to have escaped, I did notice a brief moment of change in engine idle and performance. After pulling into traffic, the engine made a "pop" and briefly ran more normally. However, the engine would not idle at all. I had to keep it from stalling by feathering the gas petal. Yet, the engine flowed through the RPM range more quickly and fluidly. Ultimately, after cooling and restarting the engine continues to idle around 2000 rpm.

Any ideas?

 
Rep Power: 518

Does the engine surge repeatedly (from 2000 to 1200, over and over)?

Did you disassemble the throttle plate from the throttle shaft?
How far did you tear this apart?

Did you remove the TPS from the throttle body?
What is the TPS voltage when the throttle is closed?


Manifold (MAP) and BARO are very different. Got the actual code? P0106 doesn't exist for a 2002 Civic.

You may want to read this thread: https://www.civicforums.com/forums/1...worse-now.html
It took a few tries before he got his IAC clean enough to work properly.

I suspect your issue might be similar to that, as in your IAC is sticking just enough to keep it from closing but CAN go wide open.

 
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The engine idle doesn't surge, the RPM stays at 2000 indefinitely. It is a vacuum leak, through the IAC.

I did not disassemble the butterfly valve or remove the TPS. Ill have to check the TPS voltage.

The IAC on there now is different than the one i cleaned, its a "new part." Symptom wise, it didn't make any difference from the IAC i cleaned.

Ill report back on the code.

 
Rep Power: 518

NOT surging? You better take a look at what the computer thinks the coolant temperature is.

When the engine is at operating temperature with throttle fully closed and the idle RPM is high, fuel cut occurs at 2k RPM and continues until 1200 RPM. (That's the 'surge'.)

You say it isn't surging, so either the TPS is saying the throttle is open, or the computer thinks the engine is still cold. Or the engine really is still cold.

 
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I unplugged the harness connector for the MAP sensor, and started the car. Idle bounces around 700-900, and obviously runs rich as hell until i turn it off and plug the MAP back in. With the map plugged in, the engine idles at 2k after start up.

ill be back with some voltage readings, and a code.

 
Rep Power: 518

Well, you WILL have a code for the MAP sensor now because of that.

You may need to erase the current codes and see what codes reset, if any.

 
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I pulled the TPS, and read its voltages.

1.11v when its fully closed,

3.02v when its fully open.

If I'm not mistaken, this range of voltages is supposed to bound between .49v and 4.49v? If thats true, then im looking at a bad TPS?

I also ran propane around the manifold using a long plastic hose, couldn't really find vacuum leaks/anything that slowed RPM.

 
Rep Power: 518

Wait, you mean you pulled it off the throttle body? You are supposed to check it in place, as installed and as used.
(If the sensor is not mounted, you could move it beyond its normal operating range.)


That ain't right.

Thereabouts, yes.

I normally see 0.49V at closed throttle, and SOMEwhere near 4.0-4.50 at WOT.....with the sensor properly mounted and properly adjusted and attached to the throttle body.

Yours is oddly narrow in range.
I'd prefer to see what the computer is seeing, on a live data list. But if this is all you can do, I guess you have to run with it.

The 1.11V with a closed throttle would explain why it doesn't surge, the computer thinks the throttle is open slightly.

Probably, but you need to check the other two TPS wires for 5Vref and ground.
If you have 5V and ground, yet your output is only what you stated when you move the throttle through its full range (open the breather so you can SEE the throttle blade move through its full range of movement?), then I'd condemn the TPS.
If anything other than 5V and ground is found there, then that needs investigated.

You stalled it when you corked the IAC passsage with your finger. You don't have a significant vacuum leak (except for the IAC being held wide open).

HTH

 
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I hope I've ruled out the possibility a vacuum leak, hah.

I looked for both the 5v reference and the ground: I got 4.99v for the reference, and .006 on the ground. Not sure if these inconsistencies would cause an issue..

Initially, I tested the TPS mounted as it was from the factory, which was 1.11v - 3.02v. I loosened it from the throttle in attempt to adjust it. Unfortunately, I couldn't get the lower bounds of the voltage range to read less than 1.11v.

I guess I need to invest in a scan tool, which one do you recommend?

I had autozone run the codes, P1106.

 
Rep Power: 518

Perfect enough for me.


Based on what you've said here, I'd say the TPS is junk.

You know Honda only sells the complete throttle body, right?

Fix the TPS, you may not need a scantool right now.

For some stuff, the next step up from plain code reader is sufficient; Freeze Frame data and basic live engine data.
Maybe a scangauge or the torque app, although I personally have never played with either to see what they have.

For deeper diagnosis, more data or bi-directional controls may be needed, which translates directly to a larger amount of money.

I personally use the factory HDS software.

 
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Yeah, I just saw the price tag on that: $272!!

I'm going to the junk yard today, ill report back!

For anyone else following along, this thread has a some very useful diagnostic information pin-pointing TPS and ECM issues.

 
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It worked.

I pulled a throttle body out of a 02 civic 4d auto, and bolted it onto my 03 civic 2d manual. I didn't even wipe it off, straight junk yard all over it.

I was under the impression IACs on manual Hondas were different than the IACs on automatic Hondas. Specifically, the number of wires at the connector. Seemingly, that is not the case.

At first, it actually idled higher at 3000 rpm. But, it kept dropping and bouncing around 1000. Eventually, it settled at 700 as I let the car sit until the ECU learned the new idle.

No MIL, no high idle, and I can get the car inspected now.

Thanks ezone!

 
Rep Power: 518

YAY



YW

The IAC valves apparently are different and I believe it has to do with the preset adjustment slots on the coil that adjusts the neutral position of the rotary valve,
but the wiring difference was on older cars.

Throttle body part numbers, DX is different from LX and EX, and
manual trans is different from automatic.
Not sure what all the differences would be other than the IAC, which would come attached to a new unit.

IAC shows different part numbers between manual and automatic.
If yours starts idling funny, you may want to swap your old IAC back onto the car.