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Thread: Idle Problems? Read this first.

  1. #1

    Post Idle Problems? Read this first.

    Idle issues are one of the most common problems that we see (this is because there are MANY things that can cause a poor idle).
    I have left this Sticky unlocked so that others may contribute their experience to this thread. Please keep your replies relevant to the topic. Please do not post your idle problems here. If you have an idle problem that is not cured by following this sticky, please create a new thread and be sure to tell us what you have already done. Please post only solutions to idle problems that are not listed in this sticky.

    IDLE PROBLEMS
    First things first: If your idle problems have developed after you have performed some manner of work on the vehicle, it is a good idea to start with the area where you have been working (i.e. – you just changed the timing belt and now you have an erratic idle. Because of this it would be a good idea to make sure that the timing is correct and all vacuum lines are intact and connected properly before moving on and trying other things).
    Obviously if you have a Check Engine Light, start by pulling the code. This will almost certainly give you a good place to start.
    Also, I have seen many threads that advise people to change the idle screw setting. Very, very rarely does this screw actually require adjustment. Although you may get a better idle by adjusting this screw, you are usually only covering-up the real problem that has caused the idle issue.

    The following items should be checked first:
    1)Worn, dirty, faulty, or incorrectly gapped spark plugs
    2)Worn/loose distributor cap and/or rotor
    3)Old spark plug wires
    4)Clogged/dirty air filter
    5)Clogged/dirty fuel filter
    6)Vacuum leak (check all lines, the throttle body gasket, and the intake manifold gasket)
    7)Vacuum lines not connected properly
    8)Incorrect ignition timing
    9)Air in coolant passages

    If the above items are in good shape, and the problem persists, try these:
    1)Remove & clean the EGR (Exhaust Gas Recirculation) valve. This valve is located on the passenger side of the intake manifold. Looks like this: EGR Pic
    2)Remove & clean the IACV (Idle Air Control Valve). This is located on the plenum of the intake manifold. Looks like this: IACV pic
    3)Remove and clean the throttle body
    4)Remove, inspect, and clean the Fast Idle Thermo Valve (Thermo valve How-To)

    If the problem is still there:
    1)Change the primary O2 sensor (Oxygen Sensor)
    2)Test the TPS (Throttle Position Sensor).
    3)Check fuel pressure at the rail. If the pressure is below 35psi, check/replace the fuel pressure regulator. If the regulator is good, fuel pump may need replacement.

    On rare/extreme occasions the following items can also cause idle problems:
    1)EGR passageways in the head/intake are clogged
    2)Fuel injectors are dirty/worn
    3)Mechanical failure/damage in the valvetrain (broken spring, bent valve, etc)
    4)Poor compression due to worn/broken piston rings
    5)Valve adjustment too tight

    NOTE: If you have changed your fuel injectors to larger aftermarket units, idle problems can arise from having too-large injectors. This is due to the pulse width becoming too short for the injectors to operate properly.
    Last edited by lynxx; 03-29-2008 at 03:25 PM.
    1994 Honda Prelude SI H23A1 / 2003 Honda VTX1800C / 1971 Mustang Drag 540cid

  2. #2

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    good write up. heres my deal:

    about 3 months ago, one day i started my car and immediately it started surging the idle from 1-2k rpms. i turned it off, started it again, and it went away. it progressively got worse from there. it started happening more frequently, but most of the times if i held the rpms at like 2.5k for like 10 seconds, it would stop the idle fluctuations and the idle would return to normal. this past week, it just wont stop. also, it sometimes does this new thing where it idles kind of "bumpy"--and if i very slowly hit the gas, it revs up in a bumpy, totally non-smooth way. I then decided it was time to do something about it, because the check engine light finally came on and i'm overdue on emissions inspection. So, i scanned it and the HDS said this:

    "IDLE SYSTEM CONTROL FAILURE

    POSSIBILITIES:
    -IAC VALVE STICKY
    -FAST IDLE STICKY
    -THROTTLE VALVE STICKY*
    -AIR LEAKAGE"

    *WTF does it mean by "throttle valve?" maybe the throttle position sensor? if anyone knows pm me! thanks

    so...after doing this i ordered the iacv part, which is a whopping 220 bucks. this pissed me off, because i put it on on Saturday, and nothing changed. just the same fluctuation bullshit.
    I then asked the master mechanic at Acura-where i work-about this, and he said next thing to do is clean the FITV.(Fast Idle Thermo Valve) I took the cover off with the gasket, sprayed cleaner in there, but to no avail...and i broke the gasket trying to put it back on.
    so now, ontop of that, coolant is leaking a little bit.
    Today, while at work, I took apart the FITV the right way - and cleaned the hell out of it w/ brake cleaner. I put it back in, and, nothing. so it turns out Acura could order this part for me, so today, i ordered a new FITV. It will be in tomorrow. i left my car there today because i think it's best not to loose more coolant.

    I am praying this works. I will let everyone know after i get off tomorrow. but given the record of this bullshit, i'm doubting it. If not, I'm going to have to find out what the HDS meant by "Throttle Valve." Again, if anyone knows, PM me please!

    I'm gonna be pissed if i have to order another part.

    any comment anybody has on this would be helpful...thanks

  3. #3

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    well, Honda took care of it today. It was the fucking PCV valve, which was totally obliterated to pieces. let this be a lesson to everyone, instead of just ordering new parts, actually diagnose the problem with a multimeter. If I had done this, I probably wouldn't have had to purchase the IACV or the FITV, saving me 280+ dollars. Ohm everything out, and this will help alot!

    If it comes down to anyone needing an IACV or FITV for the H22A4 engine, contact me, and I'll sell u my used one(s) for 1/2 honda's price. (thats $120 for the IACV and $30 for the FITV)

  4. #4

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    excellent sticky
    "As you may or may not be aware, Sweden is not a state in the United States of America. Sweden is a country in northern Europe and US law does not apply here. ...It is the opinion of us and our lawyers that you are fucking morons." -- The Pirate Bay

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  6. #6

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    after i had my timing belt changed on my 00 prelude, the idling became slightly eratic. after a few days it got worse. at cold starts it would fluctuate between 1 to 2.5 k on the rpm until it warms up. any one know what the problems might be? i spent over 2 grands trying to fix the problem. it only got worse. hate shady mechanics who don't know what they're doing.

  7. #7

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    Good search words roaming idle, jumping idle, high to low idle, surge, surging, fast, slow, bogs,

  8. #8

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    Quote Originally Posted by stocker View Post
    after i had my timing belt changed on my 00 prelude, the idling became slightly eratic. after a few days it got worse. at cold starts it would fluctuate between 1 to 2.5 k on the rpm until it warms up. any one know what the problems might be? i spent over 2 grands trying to fix the problem. it only got worse. hate shady mechanics who don't know what they're doing.
    Read the first post where it links about Fast Idle Thermo Valve.

  9. #9

    Question Am I being taken for a ride?

    We have been through the "run the codes"/"clear the codes" 3 times now at my mechanic (who has been reliable for the last 10 years...so I don't THINK I'm getting a "story").

    Original problem was a gasping-for-breath sound while idling, with the tach hopping between 1000 & 2000, and sounding like it was ready to stall out at any minute. After about 60 miles of this (one round-trip to work), the check engine light went on.

    First run of the codes found a vacuum problem ...fixed. 100 miles later, went through the whole symptom routine again...all the way to the CEL. This time the codes led to replacing the MAP sensor...plus about a week's worth of the mechanic working on re-timing the idling. 300 miles later, same routine. Codes cleared, running okay at the moment (I just got it back), but this time the mechanic says I "may have to take it to a dealership and get the ECM reprogrammed".

    (1) Does that make sense? (I thought reprogramming was only needed if you replaced an ECM?)
    (2) Any idea what a realistic cost for that is, as I check dealerships for estimates?

    BTW...2001 Prelude 5-speed manual, if that makes a difference
    Last edited by govtDrone; 03-05-2008 at 02:44 PM. Reason: typo

  10. #10

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    well this is a big help because my Prelude has a surging idle also, but it does not do it when the car is cold, once its warmed up it will surge between 800-1500 rpm's, so should i still check the same issues or is mine more clear cut cause it only does it once warmed up
    Current rides
    2000 Pontiac Firebird Trans Am LS1 6 speed...DART P&P heads,2x Cartek cam, LTheaders/fullexhaust,ls6 intake =421 hp and 398 ft.lbs
    1993 Honda Prelude Si VTEC/with JDM H22A swap
    1984 Chevy El Camino..heavly modded....under construction
    1995 Chevy 2 door Tahoe 4x4..383 cu. in. stroker, 18" '07 chrome Escalade rims
    2007 Yamaha R1

  11. #11

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    In a situation like yours, you should still check the basics (in particular the Fast Idle Thermo Valve, air in coolant, and EGR), but it is possible for the Coolant Temperature Sensor to cause problems similar to what you are describing. If the CTS is responsible, it is likely that you will have a rich condition at idle (when the engine is warm) so an inspection of the plugs can help determine if this is a possibility.
    1994 Honda Prelude SI H23A1 / 2003 Honda VTX1800C / 1971 Mustang Drag 540cid

  12. #12

    Thumbs up

    Quote Originally Posted by lynxx View Post
    In a situation like yours, you should still check the basics (in particular the Fast Idle Thermo Valve, air in coolant, and EGR), but it is possible for the Coolant Temperature Sensor to cause problems similar to what you are describing. If the CTS is responsible, it is likely that you will have a rich condition at idle (when the engine is warm) so an inspection of the plugs can help determine if this is a possibility.
    awesome, thanks for the respond man, i'll start with the FITV ,EGR and CTS.......i changed my plugs about a month ago , they were still in great shape didnt look like the engine was running rich, but i changed them anyway and gapped them properly.......i'll pull the new plugs out in a little bit and see what they like tho now after a month....

    but again thanks for the help, this has been a problem since i got the car, i should of looked into this a while ago but didnt know where to start and thought it was maybe the ECU i have in the car.....glad its not..... but the Trans Am gets priority and I only got so much time and money....... but shes just about done so, time to start fixing more shit on my Lude
    Current rides
    2000 Pontiac Firebird Trans Am LS1 6 speed...DART P&P heads,2x Cartek cam, LTheaders/fullexhaust,ls6 intake =421 hp and 398 ft.lbs
    1993 Honda Prelude Si VTEC/with JDM H22A swap
    1984 Chevy El Camino..heavly modded....under construction
    1995 Chevy 2 door Tahoe 4x4..383 cu. in. stroker, 18" '07 chrome Escalade rims
    2007 Yamaha R1

  13. #13

    Default Well don't know what to do next, was happy for a moment

    I have pulled and cleaned out the IAC, new plugs, new ignition coil (MSD Blaster 3) new ignition coil wire, Replaced valve cover gasket and tube gaskets, did valve adjustment, new thermostat, honda coolant, bled. Had a surgy idle when it got warm, did iac first then noticed sticky about fit so I just completed that. Put everything back together started her up and she idle just right a little high 1500 or a tad lower, started warming up and dropped to about 900, sounded great. Got out to take a look at the purring engine, and it cut off. Try to recrank and have check engine light with no code emmited (blinking) with the service connector jumpered.

    Please my fellow Honda Folk,
    What ya think next.
    Thanks

  14. #14

    Default Idle issues after installing cold air induction

    I noticed one thing not mentioned so even though it's been a while since anyone posted here check it.

    I purchased a 93 Prelude si H23 5 speed m/t with a cold air induction unit installed to the factory Mass air flow sensor.

    When the engine was cold the idle varied from 1500 to 2300 in a rapid cycle, then settled to around 800 or 900 once warmed up.

    Talked to a buddy-mechanic-friend of mine. He suggested this, (I am going to show this in point form for my good friend and moderator Harry):

    With the vehicle warm and idling.

    1) Turn the engine off, then turn the key back to the ON position
    2) Disconnect the negative battery cable
    3) Turn the key OFF then back ON again
    4) Go watch some Rachel Ray or a couple Kanye West videos or something
    5) Turn the key off and reconnect the neg battery cable
    6) Drive it out at normal speed to the NEAREST location to reach highway speeds
    7) Once you reach 45 mph go full throttle to 65 mph then slow back to 45 and repeat, and repeat again. You should have completed three repititions of 45 to 65 at full throttle.
    8) Go home park your car let it cool off then restart to see if the idle has settled.
    9) If so, never drive your car during cold idle. Always let it warm up first. This was my mistake and I had to do the whole process all over again.

    This little tip may save someone some up front cash. If you choose to continue with your endeavors in building a street machine you will want to add a tunable Mass air flow sensor or jump to the turbo or super charger. The cold air induction really doesn't benefit a daily driver much 2-4 hp top end so your better off just using a K&N high quality filter in place of your stock replacement. It'll give you the same benefit without the headache of the MAS problem.

    Hope this helps.

    Harry your #1


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  15. #15

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    Thanks for that info, and btw nice smiley! I've got a better one though.


  16. #16

  17. #17

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    hi im newb to this website...
    i have problem with my lude it a 92 lude with h22 swap
    when i started my car it has only 250 rpm (so i think it has a bit of problem) and if i rev iit it a bit for like 20 sec it go up to 1000 rpm and idle. i wonder is that a problem 2 the engine or not???

  18. #18

    Default h22a4 revs up and down when cold.need help

    my 01 prelude revs up and down from 1500 to 2500rpms when cold...for bout 7min..and the idles normal,,,any ideas

  19. #19

  20. #20

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    Recently my 91 auto developed idle bounce during warm up at high rev.

    I had just removed the slack from the throttle cable. I added back about 90% of the slack and the idle bounce disappeared.
    Never woulda thought the tight cable was the issue. Apparently it was though.
    John 3:16
    1991 Si 5 speed ALB
    1991 Si auto

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