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I am having some intermittent idle issues on my.

Tiny
ANONYMOUS
  • MEMBER
  • 2001 HONDA ACCORD
  • 135,000 MILES
I am having some intermittent idle issues on my accord that come very close to stalling, but it has never stalled on me as of yet. Generally the engine runs very smooth with no power issues and no missing, including at idle, but every now and then it will idle low at about 600 rpm (according to the dash gauge), but even at that low of an idle it still feel fairly smooth and is not shaking or feeling like it will still. So that is one issue, since it seems that it should be idling in the 750 rpm range.

The larger issue is that sometimes the engine will nearly stall, with some shaking, but it never actually stalls. When it does this it will typically dip down to around 400-500 rpm and then come back up on its own, or I'll rev the engine to make sure it does not stall. In nearly all cases, it only does this when I come to a fairly sudden stop, like in traffic or when coming up to a red light. Not as severe as slamming on the brakes, but just a somewhat quick stop as opposed to a regular/slow stop.

Today in traffic when I came to a quick stop on the highway, the RPM dipped all the way down to what appeared to be 100 rpm at the very bottom of the dial. The engine shook as expected, but I pushed the throttle and kept it from stalling.

What are some possible causes for this, and what tests can I do to diagnose this? Thank you!
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Friday, March 1st, 2013 AT 9:37 PM

6 Replies

Tiny
MHPAUTOS
  • MECHANIC
  • 31,937 POSTS
The obvious place to start is with the engine tune, has this been done? Clean the throttle body and clean the IAC (idle air control port) check for any unresolved fault codes, start here and report your findings for further assistance.
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Friday, March 1st, 2013 AT 10:47 PM
Tiny
BEN LEE
  • MEMBER
  • 66 POSTS
It has had a very recent engine tune up, but only basic. Spark plugs, air filter, etc, but the throttle body and IAC have not been cleaned. Do you have any info/diagrams on locating the IAC and how to go about cleaning it.

I'll go ahead and clean the throttle body, which I shouldn't have any trouble with.
Thank you
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Friday, March 1st, 2013 AT 11:08 PM
Tiny
BEN LEE
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  • 66 POSTS
I removed the throttle body and the IAC and cleaned them both. After putting eveything back together the engine is having some serious issues. Which I've obviously created. As soon as he engine is started up, it revs itself up in a continual pulsing pattern. It revs up high and then goes back down every 2 seconds or so. It is so bad that it is completely un-drivable. It is also making some type of whining noise along with the engine revving that I have neve heard before. Even though the check engine light is on, my scanner is not showing any pending or stored codes. The only thing it does say is that my "vehicle is not ready for emissions testing".

Ideas?

Due to the IAC being right against the firewall, and the mounting bolts facing the firewall, I had to remove the air intake and all the various vacuum hoses and electrical connectors, but I labeled them first to make sure I put them all back in the correct place, and I have checked many times to see if there was anything I forgot to connect or connected to the wrong place, but I can't see any issues. I'm hoping to avoid taking it all back apart again.

Thanks for your advice!
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Monday, March 4th, 2013 AT 5:46 AM
Tiny
BEN LEE
  • MEMBER
  • 66 POSTS
Update: Now my scanner is showing P0113, "Intake Air Temperature Sensor 1 Circuit High"

Freeze frame data says the intake air temp was -40 (I live in CA and it is over 50 right now, far from a negative temperature. Engine coolant temp 71. Fuel system status says "Open loop due to insufficient engine temperature"
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Monday, March 4th, 2013 AT 6:47 AM
Tiny
BEN LEE
  • MEMBER
  • 66 POSTS
Here's one more piece of info for you.I tested the ITC (intake temperature sensor) and I'm getting the following readings, which seem to be correct, but please let me know if I am interpreting the ohms incorrectly (I sometimes confuse the readings).
On the 200k scale: 003
on the 20k scale: 2.5
My repair manual says resistance should be 2,500 to 3,500 ohms with the connector removed and the engine off.

I also removed the ITC and bench tested it according to the manuel, which says to heat the sensor with a heat gun and that the ohms should lower to about 250 ohms at 180 degrees f. I don't know when I reached 180 degrees, but I do know that the ohms dropped quickly as the heat gun got warmed up. To me it would appear that the sensor is fine, but then why would I get P0113 code?

Thank you
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Monday, March 4th, 2013 AT 3:24 PM
Tiny
BEN LEE
  • MEMBER
  • 66 POSTS
FIXED! It was a vacuum leak at the back of the plenum, against the firewall. A metal hose supporting bracket was pinched between the plenum and the intake when I bolted it back together. I found it by doing a smoke test. I had no idea a vacuum leak could cause idle issues that severe, to the point of being non-drivable. No more check engine light or trouble code either.

Driving the car to work today I could see that the original idle issue that prompted me to clean the throttle body and the idle air control valave is now gone. It is idling at about 750rpm, right where it should be.
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Tuesday, March 5th, 2013 AT 3:30 PM

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