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Strange idle after cleaning TB and MAF


Megaton
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I recently cleaned my throttle body/ butterfly and mass air flow sensor according to some posts I've resd here. Afterward, I have a strange pulsing idle. The engine runs smoothly , no roughness or missing. When its started cold it goes to fast idle then it goes into this pulsing idle. When put into gear (at) it goes into fast idle again and really wants to take off. I had it put on two different scanners and the parts guy said it gave no reading at all. Like it was'nt even connected. Weird. Idle air control valve? Help me out please! Thanks, Tim.

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Same thing happend to me after cleaning the TB, "the fast idle part" May have dislodged some crusty stuff from the throttle plate and it is interfering with the IACV, or if the throttle plate was very dirty, it just has a higher idle and is trying to find the proper idle and cant quite get there.

 

I would recommend "double checking" the MAF and make sure no debris was left behind when you cleaned it. "MAF spray OR high percentage rubbing alcohol "90 percent plus" and a Q tip, very light touch and do not do it until the truck has cooled down for a while. Your MAF is a wire that uses the heat of the wire to determine air flow, if there is a piece of debris on it, it will jack up the temp reading.

If you double check the maf and it looks fine, Make sure your fast idle cam is set properly, IF the Fast idle cam is set properly, You may just need to adjust the idle screw on the back of the intake to bring the idle down to normal at fully warm operating tempature. The increased air flow through the TB will increase idle. So if it was really really dirty its a large change to the computer.

 

Hope this helps you some. The only reason i had input is because the same thing happend to me as well. Only the IDLE CAM wasnt working, after i figured that out, it was simply a matter of flipping it over backward to take it out of the equation, then adjusting the idle screw on the intake.

 

Pat

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Tried to EDIT and it was too late.

Just wanted to add as an alternative.

1. You could Drive it for a while and see if it self corrects, "like a week or a few hundred miles or whatever"

2. Make sure the ground wire on the MAF sensor plug is ok. but if it drives normal after fully warmed up it should be ok.

3. I wouldnt mess with the TPS to try to correct it, because nothing you did would really effect that, it just is a resistance vs position based sensor and it cant really get "dirty" inside it.

OK thats all i have for now, hope it works out for you.

 

Pat

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Mechanic said it was the fast idle solenoid and the only fix was to replace the throttle body. I had it done at a cost of $400 and its now running fine. After a week of driving without it self correcting I was at a loss. I was hoping it was something I could fix myself but I'm really not much of a mechanic . Thanks for the input and Merry Christmas everyone!

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It sounds kinda like when my O2 sensor went out, low idle was great, but but it had an almost rhythmic loss of power at higher idle, but plenty of power when I laid into it. You could have possibly fouled it or maybe the cat when you blew all the gunk trough. On my 95, I just unplugged the O2 harness & it ran a lot better than connected. I picked up.a new NGK sensor for about $20 & it completely fixed the issue.

 

Edit. Sorry, misread that last post, glad its running well again, I hate it wasn't the easy fix we'd hoped for

Edited by ebayfish
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fast idle solenoid? I know we have a Fast idle cam, and a Thermal element "under the intake" that controls it with an arm thatrotates the cam. Usually the part that contacts the cam arm is bent "just from what i have seen on several different R50s I am not so sure about the Solenoid. I hope he didnt adjust your intake screw and call it good and charge you 400dollars. Thats why i dont take mine to a Mechanic" parts mark up 200 percent plus, labor, 75 to 150 an hour. Half the time they BS you and when they dont, they gouge you. "shrug, to each their own"

 

Happy you got it lined out.

 

Pat

Edited by fixinto
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fast idle solenoid? I know we have a Fast idle cam, and a Thermal element "under the intake" that controls it with an arm thatrotates the cam. Usually the part that contacts the cam arm is bent "just from what i have seen on several different R50s I am not so sure about the Solenoid. I hope he didnt adjust your intake screw and call it good and charge you 400dollars. Thats why i dont take mine to a Mechanic" parts mark up 200 percent plus, labor, 75 to 150 an hour. Half the time they BS you and when they dont, they gouge you. "shrug, to each their own"

 

Happy you got it lined out.

 

Pat

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Boy I really mauled that last post . Sorry. I'll try again. I think the solenoid he was referring to was the thermal element. I do have a shiney new throttle body under the hood whether I needed it or not. I cleaned the MAF with alcohol and the TB with TB cleaner. It was running fine before I cleaned them. I did it as PM. I guess no good goes unpunished:-) Any way its running fine now. Thanks again , Tim.

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Interesting, same thing happened to me after cleaning the TB (never touched the MAF) and after two years it's still idles high. There's no idle screw adjustment on the VQs. You do have to do idle relearning either through the Nissan Consult tool or via the ignition key on/off sequence- which I did multiple times to no use. All my research showed the TB has to be replaced due to the motor control solenoid which supposedly very easily can short out. In fact, I read in some cases the bad solenoid would also short out the ECU component that controls the idle and you end up having to replace both. Personally I've been living with it but eventually I'll try to find a TB on fleabay or a the junkyard.

Edited by stioc
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yar seems like cleaning the TB, if it has been a long time since it was cleaned idles em up. Mine is a VG33 and it idled up after the TB cleaning. luckily had the screw in the back of the manifold to make it happy. Of course, mine is cable drive instead of drive by wire.

 

 

Pat.

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  • 1 year later...

Interesting, same thing happened to me after cleaning the TB (never touched the MAF) and after two years it's still idles high. There's no idle screw adjustment on the VQs. You do have to do idle relearning either through the Nissan Consult tool or via the ignition key on/off sequence- which I did multiple times to no use. All my research showed the TB has to be replaced due to the motor control solenoid which supposedly very easily can short out. In fact, I read in some cases the bad solenoid would also short out the ECU component that controls the idle and you end up having to replace both. Personally I've been living with it but eventually I'll try to find a TB on fleabay or a the junkyard.

 

Has happened to me, but I dont know what fried my ECU.

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