Rough idle

This topic contains 17 replies, has 6 voices, and was last updated by  prgonzalez 7 months, 3 weeks ago.

Viewing 15 posts - 1 through 15 (of 18 total)
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  • #1564

    ackack
    Participant

    I have a 99 Villager with only 110K miles that runs great . But, it has a very rough idle problem only while it is warming up to normal operating temperature. Once it reaches NOT it smooths out to where it has a slight tremor but entirely tolerable. Has new plugs, wires, TPS. Also MAF is clean and IACV has been cleaned but not replaced. I guess it could be something wrong with the distributor but if that was so, wouldn’t I have idle problems also at NOT? Any ideas? Thanks, John in TN

    #5538

    tracylowe
    Member

    Great post..this post is really very nice although the whole blog post are really amazing…I love to read this post..Very nice…you guys are doing great….Thanks for sharing this article.

    ——————–
    Repair Alloy Wheels

    #5539

    1999’s are noted for bad distributors. The CMP sensor (not serviceable)usually represents itself as rough idle after warm up and sometimes a tch needle that jumps around. This is due to spark firing at random. The other known issue is the bearing in the distributor failing, causing brown dust to cover the optical sensor in the disdtributor, under the rotor and cover, below the slotted wheels. Replace with new Rich Porter distributor for $200 from the Import Export Experts on their site or ebay.
    For more help, go to the villager quest yahoo group and read the files there.

    Gerry from Ford

    #5533

    prgonzalez
    Participant

    Hi John,

    Normally, the IACV will give you problems even at normal operating temperature. I would check the Fast Idle Cam (FIC). There is thermo element that compensates the throttle position as the engine is warming up. It is located at the bottom of the throttle body. look for a small hot water hose that goes to the throttle body and you will see it. The thermo element has a pin that pushes a lever that interacts with the throttle flapper. The pin is retracted in when the coolant is cold and is extended out when the coolant is hot. The lever has two marks, one for cold and the other for hot. The throttle flapper changes position from one mark to the other as the engine warms up.

    See, Engine Control System pages EC-33 and 34 of service manual.

    I hope it helps.

    Pedro

    #6262

    Abel99
    Participant

    I have a Quest 99 and is experiencing a rough idle when starting engine cold (60º);
    I have clean:
    – Clean Speed Sensor
    – Remove and clean idle control valve (spray with throttle body cleaner)
    – Clean Throttle body inside wipping with cleaner.

    The IACV in the morning idle is at the left position and after the car warm up (run good not roughness whatsoever) it moves to the left position.

    Also have change, distributor cap + rotor, put NGK spark plugs prior to developing this rough idle.

    Any ideas

    #6263

    prgonzalez
    Participant

    Maybe this helps:

    At left side of throttle body and below the cam that controls the butterfly flap of the throttle, there is a thermo-element that controls the fast idle cam. When the engine is cold, a pin in the thermo-element is contracted and the cam is in a position that forces the butterfly flap to be somewhat open allowing more air/fuel to the engine. As the engine warms-up, the pin in the thermo-element extends moving the fast-idle cam to a position where the butterfly flap closes (goes into normal operation position) allowing less air/fuel. If the thermo-element is damaged (fully extended) or not calibrated properly, the butterfly flap will not be open enough for allowing more air/fuel when the engine is cold. This is reflected in the engine RPMs. Higher when cold, lower when hot.

    There are two marks in the fast-idle cam. The cam has an adjustable screw that makes contact with the pin of the thermo-element. When cold, the cam follower lever, which is a roller on top of the fast-idle cam, will be aligned to the most left mark of the fast-idle cam. When the coolant temp is about 167-185°F, the cam follower lever should be aligned with the most right mark in the fast-idle cam.

    Check it out and report back.

    #6264

    Abel99
    Participant

    Thanks for your answer.

    When cold the pin is on top of the most left mark (rpm starts around 2000 )
    After a minute or so it goes down to 1000 rpm and then to 750 rpm and it is there when the rough idle starts.

    When engine is Hot temp the pin moves to almost to the maximun right mark but not totally. Engine works fine when is hot (no rough idle at all) .

    I will take the van to the mechanic on saturday to see if he can adjust the cam adjustable screw more to the most left position (when cold) to see if there is any effect.

    Keep you posted on results

    Thanks a lot

    #6267

    prgonzalez
    Participant

    Abel99,

    If the engine runs fine at high idle when engine is cold and when fully hot, the engine is going too quickly from high RPM into normal RPM (750). Then is reaching 750 RPM normal idle when the engine in reallity is still cold. You have now two options: either a better adjustment of the fast idle cam will help, or the termo-element is bad and reacts too fast with the coolant temp. You might need to replace the thermo-element. By the way, the correct adjustment of the fast idle cam is done using the coolant temperature of 167°F to 185°F as the reference for the right mark. When the coolant is cold 68°F to 86°F the rod must align with the left mark.

    Keep us posted.

    Pedro

    #6285

    Abel99
    Participant

    I have changed the IACV yesterday and throttle clean and the car keep doing the same idle problem when cold. I am following your suggestion and will get a new termo-element valve and have it change next week and see if that takes care of it.

    In order to try to adjust the screw of the fast idle cam when car is hot (167f-185f) it will not affect the manufacture setup of that setting?
    Mechanic say that if we touch that screw he will not be able to reset it at the original setting that was done by factory my question is once I start to adjust it and try to make it move to the right at (167f-185f) what exactly i am supposed to expect to happen when adjusting? Should the engine idle smoothly or what it will happen? for me to say “there”.

    By the way I already changed distributor 2 year ago.

    Hoppe you follow me on this one Pedro. Last what will be the correct name of the “termo-element valve” or you know were can I get it online? Thanks

    Keep you posted
    Abel

    #6287

    prgonzalez
    Participant

    Abel,

    The temperature settings I provided you are the manufacturing set points. The adjusting procedure is to check the cam at two different temperatures. The roller on top of the fast idle cam has to be around the LEFT mark when coolant is 68-86°F and above the RIGHT mark when coolant is 167-185°F. If I have to chose between which mark to be more acurate, I would chose to align with the RIGHT mark at 167°F. If the marks do not position at those temperatures, then the thermo-element is bad and needs to be replaced. Last time I checked with Nissan they told me it cost around US$100.

    In easy to understand terms, the function of the thermo-element is to regulate the engine RPMs from cold to hot. RPMs are set to high when engine is cold and are gradually reduced as the engine warms up. In your case, I believe, the thermo-element is sending the lever to the lowest idle RPM (approx 750) while the engine is still too cold, causing erratic idle. I am not sure if you remember this, releasing the choke valve too soon in old cars?

    For a good adjustment, your mechanic needs a scanner to read the proper coolant temperature. If your mechanic does not have a scanner for reading the correct coolant temperature, then do not let him touch the setting and look for another mechanic that has a scanner.

    By the way, I re-adjusted the fast idle cam in my van about two years ago. I did it because I disassembled the whole throttle body to take care of a coolant leak I had in the thermo-element. I replaced the O-ring that seals the thermo-element. The adjustment was easy with a scanner.

    Pedro

    #6304

    Abel99
    Participant

    Hi Pedro,

    As you say my mechanic doesn’t have the scanner and I’m wondering if places such as Pep-boys, sears or Firstone garages will have such devices.

    My question maybe if there is any other way I can measure the temperature (gage or something) where I can detect 167-185°F.

    Most important is from where this temperature measurement should be taken (radiator or something)?

    Thanks again for your patience

    Abel

    #6305

    prgonzalez
    Participant

    Abel,

    I bought my scanner online. I bought the ACTRON CP9180 for close to US$200.00. Great investment since I have three cars including the van.

    I do not want to be offensive about your mechanic. But in my opinion, any shop dedicated to do a good job should have at least one of these or equivalent.

    The scanner reads the temperature from the computer. The temperature sensor goes connected to the computer. The computer uses it for various functions.

    There is another way of reading the temperature by reading the voltage of between terminal 59 at the ECM (computer) and ground. Initial voltage should be between 3.12 and 3.52V for the LEFT mark. As the engine warms up, when the voltage drops between 1.10 and 1.36V the RIGHT mark should be aligned with the roller on top.

    If the mechanic can identify terminal 59 at the ECM, then he could adjust the fast idle cam. The only care he has to take is not to make any short circuit in the ECM when reading terminal 59.

    My experience with Firestone places or similat has not been pleasant. Therefore, I do not recommend them at all. I just trust them for wheel alignment and balancing and still check everything of my auto before and after their work.

    Hope it helps.

    Pedro

    #6306

    Abel99
    Participant

    Hi Pedro and thanks again,

    You really know your trade. I wish you were somewhere near Miami Florida.
    I am afraid I will have to take the van to the Nissan dealer because we don’t have the scanner not the ECM computer to read the voltage from the terminal 59.

    Thanks for telling me about your appreciation 3 party garages ( I feel the same);

    Question: If NISSAN tells me that the thermal element is bad then the replacement of the thermo element need to be adjusted also with the scanner right?
    The reason behind is that I was trying to adjust the thermo element first and see before buying the part but if to replaced it will required the scanner then my mechanic will not be able to do it anyway. So in other words I don’t have another alternative that to take it to the dealer.

    Thanks again And I will keep you posted

    Abel

    #6307

    prgonzalez
    Participant

    Abel,

    It is my pleasure to be able to help in this forum. I love my van as she have gave me so many hours of pleasant driving time in long trips.

    Your Nissan dealer will help you 100%. Just be ready for the hit. If they have to replace the thermo-element, I can see they will easily charge you a minimum of two hours plus the part. If it is just adjustment, it should be less or equal to 30 mins of labor.

    I noticed that my van take more then two minutes to go from high RPM to normal operating 750 RPMs. Yours should be about the same. I am in Houston and you in Miami. I believe the ambient temp is about the same these time.

    Pedro

    #6323

    Abel99
    Participant

    Hi Pedro,
    Finally I got it running fine. My mechanic took it to a friend master mechanic and he went over all the things we have done before; he went ahead and did this again:
    – Remove and clean idle control valve (spray with throttle body cleaner)
    – Clean Throttle body inside wipping with cleaner.
    then he replace the distributor but it didn’t work either. then he remove the rear sensor located in the opposite side of the IACV and clean it good; he discovered a leak on a small hose that contained coolant and fix it (maybe there was the problem); then he assembled everything together and it worked.

    I have to thank you for all your input and I hope this description allows you to figured out was what wrong as the thermo-element was OK.

    Anyway Pedro thanks again, I learned a lot from this experience I hope this interchange may help somebody else,
    ABel

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