mkeene

Hey Everyone,

*Skip this paragraph for a bullet-point summary of the symptoms but I'll give the full sequence of events and observations here from everything I've done so far for reference*
I'm having a major problem with my Accord (2000 Honda Accord LX (F23A1 VTEC Engine / US Model). It all started when I took it in for the annual state inspection (I live in PA, it sucks) and while it passed with flying colors, the tech mentioned that my sticky gas pedal (only on first press) was due to carbon buildup in the throttle body and should be cleaned (quoted $178, no thank you). Instead I watched the videos and found out how to clean it myself so I bought Valvoline TB Cleaner, pulled the intake off the TB, sprayed the sucker down and wiped it all up. Lots of black stuff came out and afterwards the inside was shiny and spotless. That night (a few hours later) starting the car was a little rough (but the video said to expect that so I didn't panic) but smoothed out to normal idle and I was on my way. But once I reached operating temp things went haywire. In drive, the car is accelerating in bursts without throttle input. In park and neutral, the idle jumps from 1100rpm to 2100rpm, back and forth ("hunting idle"?), but only once the engine is warmed up. Until it reached operating temps from a cold start, it idles fine (high as expected until temp is reached). Then, just today, the problem evolved. In drive, while moving, I lost response from the gas pedal for a moment, the check engine light came on, and I can no longer rev the engine past 3000rpm. Below that I can keep the car moving but very sluggishly and from a stop the car almost stalls before moving. On acceleration upon hitting the ~3000rpm mark the RPMs bounce very quickly up and down between ~2900rpm and ~3200rpm and even pedal-to-the-medal I can not get the RPMs past this. I read the codes since the CEL came on and pulled P1129 (MAP sensor), so I started tinkering with it. First I confirmed the connector is giving it 5v of power and the ground is not broken/shorted, then I went into the OBD-II monitors and saw the the MAP is giving a reading that changes with rpm/throttling, but beyond that I don't know if the readings are what it SHOULD be giving or how to test further. Also, based off of some other research on idle problems in Hondas, I figured perhaps the Idle Air Control Valve could be at fault. So back when my problem was JUST the hunting idle, I took off the intake hose to the TB and covered the port that leads to the IACV with my finger (the port in front of the throttle blade on the left) and observed that on closing it entirely, the car stalled (as expected if I understand it's purpose), BUT if I covered it 90%, I had a perfect idle. What that means, I have no idea. Fast forwarding to today, when I disconnected the MAP entirely, the car idles perfectly, BUT in drive or reverse the car stalls on any pedal input. Besides the point that maybe you can't drive without an MAP connected (I needed a laugh), I don't know what that tells me. Is it my IACV? My MAP sensor? Or do those observations and results point at the third possibility? Any suggestions or other diagnostic ideas would be greatly appreciated as those are both not very cheap parts and I'd like to be sure of the problem before I throw parts at it.

In summary, this is what I've got
- After cleaning the throttle body, I have a warmed up idle hunting back and forth between 1100rpm and 2100rpm. Cold idle is fine until warm-up
- The next day, a check engine light came on and I briefly lost power to the pedal
- Check engine code was P1129 (MAP sensor)
- Car now can't go past 3000rpm without bouncing rapidly between ~2900rpm and ~3200rpm, and is slugging/nearly stalls from a stop
- Unplugging MAP solves the idle problem but not the high-rpm bouncing and car stalls in drive or reverse with MAP disconnected
- Plugging the IACV port (which has intense suction) with my finger entirely, stalls the car, but covering it 90%, makes the car idle perfectly (with MAP connected)

If you made it this far, thank you for reading and in advance for any help. I've spent 3 days non stop trying to learn these systems and diagnose but I've hit a wall and could use some more educated guidance as I'm relatively new to DIY car maintenance. Happy Wednesday!

bestofthe80s

I had an idle surge with my 2001 accord 4cylinder sulev car as well. I tried cleaning out the throttle body as well with not much improvement. I ended up removing the TB, cleaning it thoroughly. I also removed the Intake Air Control Valve (IACV) on the back of the intake. This thing was seriously gummed up... I sprayed it with intake cleaner and began moving the parts inside... they were seemingly fused together with black carbon build up. After a few minutes it freed up and began clicking and rotating like it's supposed too. I replaced it and put a new gasket on the TB. Idled like a kitten afterwards.

ISUBIEXI

IACV and MAP deal with Vacuum. Vacuum is super important in our cars, the ECU uses the vacuum pressure, measured by the MAP to determine fuel maps and I assume timing. Check for Vacuum leaks, that's always the first step. Assuming that there is no leaks the next step is the IACV as best said above. The IACV is basically a controlled Vacuum leak to let just enough air in to keep the car idling smoothly with the throttle body closed. Just a note, its possible that there is a leak around the throttle plate or elsewhere that the carbon was sealing.

It kind of sounds like the IACV is stuck open. Take it off and clean it as explained above. You may want to get a new o-ring ordered in advance just in case.

If your car is throwing a code it will be in limp mode and performance will be severely limited. Fix the idle, reset the ecu/clear the code and go from there. It may be a simple fix.

holmesnmanny

If it were me I would probably replace the oring that seats the map sensor on the throttle body. Perhaps it got damaged when you sprayed the throttle body. Throttle body cleaner has a way of swelling orings and rubber material.

mkeene

UPDATE!

Victory!!! Y'all rock hardcore. Thank you so much. Figured out how to yank off the IACV, soaked and cleaned the crap out of it (it was NASTY in there; I think yea some of the carbon I let loose with the TB cleaner got sucked up into it and piled up), removed and replaced the gasket and o-ring, and VOILA! She purrs like a kitten, can pedal to the medal smooth, and the CEL went off on its own; I didn't even need to clear it. Now to tackle my A/C leak before it hits 100F out here haha.

Thanks again guys! <3

holmesnmanny

it actually sounds more like you had the iacv and map sensor connectors swapped since you will never throw a code for the map sensor unless something is wrong with the map sensor circuit

mkeene

On my vehicle thats not even possible, the IACV and MAP connectors are on different ends of the throttle body and can't reach each other.

ISUBIEXI

You can mix up the EGR and Map plugs quite easily but the IACV is generally out of range for the plug.

andrewtmedley52

I had the same problem. Took it to the shop and they wanted $900 to R&R the iac valve. I pulled it and cleaned it myself. Also cleaned the TB, but didn't pull it. Put is all back together and the idle is fine now, but it still bounces like crazy 2900-3100ish rpm. any ideas?

JDMPreludePower

[QUOTE=mkeene;51305741]Hey Everyone,

*Skip this paragraph for a bullet-point summary of the symptoms but I'll give the full sequence of events and observations here from everything I've done so far for reference*
I'm having a major problem with my Accord (2000 Honda Accord LX (F23A1 VTEC Engine / US Model). It all started when I took it in for the annual state inspection (I live in PA, it sucks) and while it passed with flying colors, the tech mentioned that my sticky gas pedal (only on first press) was due to carbon buildup in the throttle body and should be cleaned (quoted $178, no thank you). Instead I watched the videos and found out how to clean it myself so I bought Valvoline TB Cleaner, pulled the intake off the TB, sprayed the sucker down and wiped it all up. Lots of black stuff came out and afterwards the inside was shiny and spotless. That night (a few hours later) starting the car was a little rough (but the video said to expect that so I didn't panic) but smoothed out to normal idle and I was on my way. But once I reached operating temp things went haywire. In drive, the car is accelerating in bursts without throttle input. In park and neutral, the idle jumps from 1100rpm to 2100rpm, back and forth ("hunting idle"?), but only once the engine is warmed up. Until it reached operating temps from a cold start, it idles fine (high as expected until temp is reached). Then, just today, the problem evolved. In drive, while moving, I lost response from the gas pedal for a moment, the check engine light came on, and I can no longer rev the engine past 3000rpm. Below that I can keep the car moving but very sluggishly and from a stop the car almost stalls before moving. On acceleration upon hitting the ~3000rpm mark the RPMs bounce very quickly up and down between ~2900rpm and ~3200rpm and even pedal-to-the-medal I can not get the RPMs past this. I read the codes since the CEL came on and pulled P1129 (MAP sensor), so I started tinkering with it. First I confirmed the connector is giving it 5v of power and the ground is not broken/shorted, then I went into the OBD-II monitors and saw the the MAP is giving a reading that changes with rpm/throttling, but beyond that I don't know if the readings are what it SHOULD be giving or how to test further. Also, based off of some other research on idle problems in Hondas, I figured perhaps the Idle Air Control Valve could be at fault. So back when my problem was JUST the hunting idle, I took off the intake hose to the TB and covered the port that leads to the IACV with my finger (the port in front of the throttle blade on the left) and observed that on closing it entirely, the car stalled (as expected if I understand it's purpose), BUT if I covered it 90%, I had a perfect idle. What that means, I have no idea. Fast forwarding to today, when I disconnected the MAP entirely, the car idles perfectly, BUT in drive or reverse the car stalls on any pedal input. Besides the point that maybe you can't drive without an MAP connected (I needed a laugh), I don't know what that tells me. Is it my IACV? My MAP sensor? Or do those observations and results point at the third possibility? Any suggestions or other diagnostic ideas would be greatly appreciated as those are both not very cheap parts and I'd like to be sure of the problem before I throw parts at it.

In summary, this is what I've got
- After cleaning the throttle body, I have a warmed up idle hunting back and forth between 1100rpm and 2100rpm. Cold idle is fine until warm-up
- The next day, a check engine light came on and I briefly lost power to the pedal
- Check engine code was P1129 (MAP sensor)
- Car now can't go past 3000rpm without bouncing rapidly between ~2900rpm and ~3200rpm, and is slugging/nearly stalls from a stop
- Unplugging MAP solves the idle problem but not the high-rpm bouncing and car stalls in drive or reverse with MAP disconnected
- Plugging the IACV port (which has intense suction) with my finger entirely, stalls the car, but covering it 90%, makes the car idle perfectly (with MAP connected)

If you made it this far, thank you for reading and in advance for any help. I've spent 3 days non stop trying to learn these systems and diagnose but I've hit a wall and could use some more educated guidance as I'm relatively new to DIY car maintenance. Happy Wednesday . Thanks for some of your diagnosing it help me out some.I have a similar problem my prelude starts sputtering at about 4000rpm but mine luckly dose go over 4000rpms

JDMPreludePower

[QUOTE=JDMPreludePower;51603260][QUOTE=mkeene;51305741]Hey Everyone,

*Skip this paragraph for a bullet-point summary of the symptoms but I'll give the full sequence of events and observations here from everything I've done so far for reference*
I'm having a major problem with my Accord (2000 Honda Accord LX (F23A1 VTEC Engine / US Model). It all started when I took it in for the annual state inspection (I live in PA, it sucks) and while it passed with flying colors, the tech mentioned that my sticky gas pedal (only on first press) was due to carbon buildup in the throttle body and should be cleaned (quoted $178, no thank you). Instead I watched the videos and found out how to clean it myself so I bought Valvoline TB Cleaner, pulled the intake off the TB, sprayed the sucker down and wiped it all up. Lots of black stuff came out and afterwards the inside was shiny and spotless. That night (a few hours later) starting the car was a little rough (but the video said to expect that so I didn't panic) but smoothed out to normal idle and I was on my way. But once I reached operating temp things went haywire. In drive, the car is accelerating in bursts without throttle input. In park and neutral, the idle jumps from 1100rpm to 2100rpm, back and forth ("hunting idle"?), but only once the engine is warmed up. Until it reached operating temps from a cold start, it idles fine (high as expected until temp is reached). Then, just today, the problem evolved. In drive, while moving, I lost response from the gas pedal for a moment, the check engine light came on, and I can no longer rev the engine past 3000rpm. Below that I can keep the car moving but very sluggishly and from a stop the car almost stalls before moving. On acceleration upon hitting the ~3000rpm mark the RPMs bounce very quickly up and down between ~2900rpm and ~3200rpm and even pedal-to-the-medal I can not get the RPMs past this. I read the codes since the CEL came on and pulled P1129 (MAP sensor), so I started tinkering with it. First I confirmed the connector is giving it 5v of power and the ground is not broken/shorted, then I went into the OBD-II monitors and saw the the MAP is giving a reading that changes with rpm/throttling, but beyond that I don't know if the readings are what it SHOULD be giving or how to test further. Also, based off of some other research on idle problems in Hondas, I figured perhaps the Idle Air Control Valve could be at fault. So back when my problem was JUST the hunting idle, I took off the intake hose to the TB and covered the port that leads to the IACV with my finger (the port in front of the throttle blade on the left) and observed that on closing it entirely, the car stalled (as expected if I understand it's purpose), BUT if I covered it 90%, I had a perfect idle. What that means, I have no idea. Fast forwarding to today, when I disconnected the MAP entirely, the car idles perfectly, BUT in drive or reverse the car stalls on any pedal input. Besides the point that maybe you can't drive without an MAP connected (I needed a laugh), I don't know what that tells me. Is it my IACV? My MAP sensor? Or do those observations and results point at the third possibility? Any suggestions or other diagnostic ideas would be greatly appreciated as those are both not very cheap parts and I'd like to be sure of the problem before I throw parts at it.

In summary, this is what I've got
- After cleaning the throttle body, I have a warmed up idle hunting back and forth between 1100rpm and 2100rpm. Cold idle is fine until warm-up
- The next day, a check engine light came on and I briefly lost power to the pedal
- Check engine code was P1129 (MAP sensor)
- Car now can't go past 3000rpm without bouncing rapidly between ~2900rpm and ~3200rpm, and is slugging/nearly stalls from a stop
- Unplugging MAP solves the idle problem but not the high-rpm bouncing and car stalls in drive or reverse with MAP disconnected
- Plugging the IACV port (which has intense suction) with my finger entirely, stalls the car, but covering it 90%, makes the car idle perfectly (with MAP connected)

If you made it this far, thank you for reading and in advance for any help. I've spent 3 days non stop trying to learn these systems and diagnose but I've hit a wall and could use some more educated guidance as I'm relatively new to DIY car maintenance. Happy Wednesday .

JDMPreludePower

Thanks for your diagnosing it help me out some.I have a similar problem my prelude starts sputtering at about 4000rpm but mine luckly dose go over 4000rpms