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Discussion Starter #1
2007 Versa S.
After replacing valve cover gasket, replacing coils/plugs, cleaning throttle body, and replacing PCV valve, I have high revs on idle or neutral (close to 2K) and after some warmup there is pulsating idle (maybe 2.3K to 1.5K repeatedly).
When in drive, when braked the revs are somewhat lower and do not pulsate. Car is still somewhat drivable but at too high base revs.
Driving engine operation is smooth, not clunky, so it doesn't seem like it's just a one-cylinder problem.
The only trouble code is P0507 (idle air control system), no others.
Have already repeatedly tried the throttle relearn procedure a few times, with engine properly warmed, but the CEL never turns solid (never stops flashing) like it should in the last step.

Do the above symptoms point MORE toward any one of the following three? or to anything else?
  • electronic throttle control needs replacing
  • vacuum leak
  • PCV system problem
So far I've tried finding vacuum leak with the brake cleaner technique, and could not detect any idle change, but it's hard to reach back of throttle body and most areas around the valve cover gasket on this car.
 

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Look at the TB work, vacuum leak. If you reused the gasket a mistake. The idle code means the ECM cannot control the idle due to the leak. Relearn is a waste of time if the computer cannot control 100% of the air coming in there, it will NEVER take.

If you cleaned TB with solvent to damage the throttle shaft seals or TPS then the TB may be ruined.
 

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Discussion Starter #3
Hi Amc49! It's nice to have a normal discussion that's not about "coronavirus"!

Any other DIY way to check vacuum leak besides the brake cleaner trick?

I used brake cleaner as solvent (with a toothbrush) because I read that the formulation is basically same as throttle cleaner. Didn't read anything about throttle shaft seals, but I brushed around shaft too. I hear the thing clicking during one of the relearn steps.
 

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If you are leaking at a possible internal idle bypass molded into the TB base gasket you will not detect that with outside checking. You didn't respond on the gasket reuse thing either. No sense in further checking without that gasket new, but if you have the ability then look at fuel trims, if going up and O2 is switching at lower than midpoint average you have a leak.

The high idle speed not controlled is proof of a leak. ECM is telling you it has closed TB as far as it can but the idle speed still cannot be lowered enough.

Occasionally a wrong PCV valve may meter too much air to do it. Some cars use the same type on various cars, the only difference being the metering hole plate inside the part, outside will look the same.
 

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Discussion Starter #5
Hi Amc49 and anyone else reading this. Just FYI, I tried the Nissan idle relearn procedure some more and it finally solved the problem without buying any more parts or searching for vacuum leaks. There are many slight variations posted on the relearn procedure, but here's what eventually worked for me:

CONDITIONS: Check Engine Light (CEL) with P0507 trouble code and high/pulsating idle, after disconnecting and reconnecting electrical to throttle position controller such as when cleaning throttle body.
TOOLS NEEDED: stopwatch or timer showing seconds.
1. When engine COLD, first perform the Accelerator Released Position and then the Throttle Valve Closed Position procedure.
2. Warm up engine at this point. I drove around my neighborhood for a bit less than 10 minutes despite somewhat high base revs in drive.
3. Car in Park, turn off all electrical powered stuff, wheels turned straight.
4. Turn key OFF and wait at least 10 seconds.
5. Turn key ON (not ignition) and start stopwatch at same time.
6. When stopwatch is at 3 seconds, press & release accelerator pedal 5x hard and quickly.
7. When stopwatch is at 15 seconds, press accelerator pedal and keep it down.
8. Approx when stopwatch shows 27 seconds, the solid CEL goes out then starts blinking. Keep the accelerator down. If the CEL never starts blinking, then something is not working and you'd better start over again.
9. When the CEL becomes solid again (stops blinking) about 10 seconds later, immediately start the engine and let it idle. It will still likely be a high-rev/pulsating idle.
10. Let it run for about 20 seconds and rev the gas a few times.
11. With foot on brake, shift into Drive. Idle will now go WAY down under 1000rpm. Shift to Park again, and the car will find its regular idle speed, and purr like a rather quiet kitten again. Operation will be normal except CEL will still be on. It may disappear soon on its own, or you can do the following:

EASY RESET OF CHECK ENGINE LIGHT (CEL)
1. Turn key OFF and wait at least 10 seconds
2. Turn key ON (no ignition), wait 3 seconds, then press & release accelerator 5x hard and quickly.
3. Wait 10 seconds, then fully press accelerator.
4. After about 12 seconds CEL will go off then start blinking. As soon as it starts blinking, release the accelerator.
5. Wait 10 seconds, then fully press accelerator again.
6. Wait 10 seconds, then release the accelerator again.
7. Turn the key to off, then immediately start the engine. The CEL should be gone now.
 

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I feel that if nothing proves out to be wrong with the car then there is no need to jump through all of those hoops. The ECM should tune the TB back 100% fully by itself. I must admit of course that I have not messed with them that much as I have never had any of the trouble people say. But at some point I will get a TB apart to see how constructed and then i will likely come up with an easier way to get back to idle 'zero', or the nominal idle point without all that bullsh-t.

Don't laugh, I have done some what appear to be non-conventional things to zero the Fords in with problems very similar and the methods are much easier than all that is. It all begins with a TB with a butterfly in a certain position and the TB TPS switch (or whatever reading takes its' place) showing where it is staged at to begin with before anybody removes a TB to change things up. This problem is very similar to all the monkey-motion that takes place on Ford DOHC engines trying to get the cams back in original running position with no marks on them and undone to be willy-nilly and nobody knows how to time them with VCT. I developed an easy procedure that removed pages of bullsh_t from the Ford service manual as a waste of time and way easier to do with dead on results 100% of the time.

The point being..........if the engine ran before with the TB in a certain position as long as one knows exactly what that 100% means then it will run again with all that correct before you establish power to the TB to start car back up after the work. Without doing any of that at all. Why? because all the work you guys are doing is simply to get the TB exactly back to the same exact position at butterfly it was before you ever touched it. Like the cam thing mentioned above. If the TB was cleaned it will be so close it may as well be the same as the butterfly will only vary maybe .005" in position from where it was before. The ECM should be able to auto adjust that with no messing with it at all.

Something in physically cleaning them or other action is throwing that way off to make y'all have to do all of that. I can tell by what you are doing with that procedure. Gradually sneaking back up on the original position the butterfly was at before.
 

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Discussion Starter #7
Acm49 you obviously have a lot of great experience. In searching for info about the Nissan idle relearning, I did come across one account that sounds similar to what you mention. One guy said he never did the relearn procedure: his car just ran wonky for a week or two before it settled back into a good idle. I didn't want to risk that: mine was running just too weird to want to take it on the highway!
 

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I have run into no bad running at all so far. Didn't even have to relearn absolute throttle 100% on or off.

Obviously, if one has to move the TB butterfly any at all to get to the edges for cleaning it must go back in the exact same place it was before. I know how to do that on the Fords but have not had to do it yet with Nissan. I will go there when I have to and then likely come up with something.
 

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Discussion Starter #9
I think I know what you are saying, Amc49. Assuming there is an actual adjustment of the butterfly valve for idle, it must be very slight. I don't quite understand why/how this relearn procedure works, but it finally did.
 
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