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Discussion Starter · #1 ·
2007, AWD with 161,750 miles.

Check Engine Light is OFF.

In park or neutral, there is no noticeable stumble. If the A/C is OFF, there is a minor stumble when waiting at a traffic light.

All spark plugs and ignition coils were replaced at 120,000 miles so I have about 42,000 miles on the replacements.

I replaced the air filter, cleaned the MAF, and filled the tank with 15 gallons of 93 Octane at 161,710 miles and that seemed to help considerably. The air filter was really dirty.

I replaced the PCV valve at 161,740 miles and that didn't make any difference.

I have not removed all of the duct work between the throttle body and he plastic resonator. I only removed the section between the resonator and the air filter intake.

Other than checking the throttle body and cleaning it, without any check engine light on for any diagnostic codes, what would be best to check next?

Is the fact that the stumble is worse with the A/C turned on, mean anything specific or is it simply because it adds an extra load on the engine.
 

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Discussion Starter · #2 ·
Since last evening, I have been searching on-line and I have found that there are a lot of people that suggest that twhen you have any idle issues without any check engine light on or diagnostic codes present that the throttle body needs to be removed and thoroughly cleaned with Intake/Throttle Body cleaner and that would be followed by a throttle function relearning procedure. There appears to be some disagreement on a couple of the delay/wait times between some of the steps in the procedures.

There are some people that say "DON'T TOUCH THE THROTTLE BODY!!". And one other that said that some technician at a dealership said that most cleaners will remove some "dry lubricant" that is used - I assume on the pivot ends of the throttle body butterfly.

Does the simple removal of the electrical connector from the throttle position sensor require the relearning procedure or that you most likely manually open and close the butterfly a couple of dozen times while cleaning the throttle body?

I have searched this forum and I've found nothing definitive to help me.

In 13+ years and nearly 162K miles, the throttle body on this 2007 FX35 has never been cleaned or serviced by anyone.

I would imagine that if I decided to buy a remanufactured Hitachi throttle body that I would definitely need to have all of the relearning procedures performed.
 

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I know it's been a few years since this was Posted, so just know this, that stumble is from a leaking vacuum line.
When you're AC is switched on, your engine idle is increased to spin the compressor at a more efficient speed to compress the freon.
If you take a weekend to inspect your entire vacuum system you'll find the culprit.
Good luck.
 

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Discussion Starter · #4 ·
As far as a leaking vacuum line, I haven't found any - yet.

I did find that the underside of the rubber intake duct closest to the throttle body was ripped totally through on the underside where you couldn't see it. It was actually ripped/cracked about 180 degrees around!

I bought a new piece that just arrived this week and I replaced it this morning. After driving about 15 miles, the check engine light came on! I now have 161,988 miles and a P0305 for a misfire on the #5 cylinder.

I think that #5 is the one on the passenger side at the back of the engine. I find it odd that I didn't have any check engine light until I replaced the leaking duct to the throttle body? I don't think that I disturbed the throttle body butterfly valve when I was pulling the old duct off or putting the new duct on.

Is there a way to test an ignition coil? I have not seen an NGK plug fail after just 42,000 miles. I've also not seen NGK plus sold individually. They usually come in packs of 4 or 6. I'm going to have to look to see if I kept the original plugs with 120,000 miles on them and swap them out. I know that I don't have the old ignition coils.

If I did accidentally "tweak" the throttle body butterfly valve, would that cause a P0305 and I need to go through that weird "throttle position relearn" procedure that I've read about?

I have never replaced any of the fuel injectors so they all have 161,988 miles on them. I really do not want to get into a parts replacement circus trying this or that. Is there a way to check the fuel pressure at each injector?

Thanks.
 

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Yes. to check to see if it is the plug or the coil you just swap them to a different position, clear the code, and see if the code changes. That is, if it comes back again.
 

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Discussion Starter · #7 ·
My 2021 isn't going very well. I was thinking that I would go through the throttle position relearn procedure that I found and I got out my digital multimeter to test the battery. I forgot to take the two AAA batteries out of it the last time I used it and one leaked. I cleaned up the contacts but now the meter reads high on everything. A simple 1.5v AAA or AA battery reads at 1.625v, a 9v transistor radio type baettery reads about 11.25v. The battery in my truck reads 17.25v. And the battery in the FX35 reads 16.5v. I can't trust this meter anymore. What a stupid thing to have not removed those batteries.
 

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Discussion Starter · #8 ·
It's been 4 months since I started this thread and due to COVID closures, our FX35 has been sitting. I replaced the battery. The check engine light has been off. I think that the misfire code showed up after the initial drive after cleaning the throttle body with intake cleaner.

Anyway, the car seemed to run a little better after I replaced the battery. I'm wondering if a throttle closed position "code" was reset because the car didn't have anything powered for about 20 minutes.

I went through the throttle position relearn procedure that I found on YouTube. That has not seemed to make any improvement,

I have not found any vacuum leaks but this car isn't like a 1980's GM V8 with rubber vacuum lines running around all over the engine that dry and crack. Any suggestions on where to look/listen for a vacuum leak?

The car now has 162,028 miles on it or only about 260 miles since this stumble started when sitting at traffic lights with the A/C on. The car stumbles slightly when the A/C is off but it's not terrible. Since it's summer, driving without the A/C on is miserable so we've not been using the car.

There is one service station that I trust to not rip me off. Do I need to have my throttle body removed and "professionally" cleaned? Maybe he can find a vacuum leak with his diagnostic tools?

Could this be a clogged or weak fuel injector or fuel pump?

Thanks for any further suggestions.
 

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One time my 2005 FX35 suddenly booged down and stalled after I gunned it.

I had previously cleaned the throttle body. I used throttle body cleaner/swabs/rags and cleaned the butterfly flapper, I didn't remove the throttle body itself. Super simple.

So I knew it wasn't that.

But I read about a guy who had an insect in his MAF.

Son of a bitch! That was it, I sucked up a dead bee and after I carefully removed the bee - everything returned to normal.

Similar to you, I parked the FX35 a year ago due to Covid (home office). The car started had started running crappy, and was not throwing a CEL, but the code said misfire in cyl 6, and I didn't want to deal with it, so the car just sat.

Today I got it started, and it's still running poorly, so I'm gonna try the coils/plugs.
 

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Discussion Starter · #10 ·
On Monday Oct. 11, I had the throttle body removed and cleaned by an auto service business that I trust. I could not get the lower right bolt out of the throttle body to remove it to clean it myself and I decided to not go and buy several different length 5.5 mm hex wrenches to allow me to get it out. After cleaning and reinstalling with a new gasket and performing the idle air volume relearn procedure and also running fuel injector cleaner through the tank, the idle was better but not what it used to be before this nonsense started around April. I keep seeing and reading posts from people that are having idle and stalling issues. What the heck is going on with so many FX35's?

Anyway, the owner of the shop called me this morning (Oct. 12) to tell me that he was about to use his scan tool on someone else's car and all of the data from our FX35 was still in the memory so instead of deleting, he looked at all of the screens of data. He thinks that I should try to replace the ignition coil on cylinder #5 that gave me a misfire code back in June when I had sprayed throttle body cleaner liberally into the intake. He thinks that the data from #5 is a little "weak" compared to the other ignition coils.

About 20,000 to 25,000 miles ago, I had replaced all 6 coils and spark plugs and the coils are under a lifetime warranty from Advance Auto so he suggested that I replace that coil and see what happens.

Anyway, one question that I have for everyone is related to the Throttle Valve Closed Position Learning Procedure. Does anyone know what the sound would be that confirms that the throttle valve "moves"? I hear the fuel pump pressurize and I hear a click that I have always associated with the fuel pump finishing it's pressurization with the ignition on and off dance. Is this click the operating sound for the throttle valve closing?

I also have read that there is a MAF reset procedure where you pull the connector off of the MAF and you are supposed to run the car at idle for at least 3 seconds. Then you verify that you get a diagnostic code for a MAF failure, reset the code, and the MAF should be reset. Has anyone else done this reset procedure?

Thanks.
 

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Discussion Starter · #11 ·
Update - I replaced the ignition coil and NGK plug on Cylinder #5 on Oct. 13. After 3 cold starts and 3 hot starts and 20 miles of driving in traffic with the AC on and the AC off, the idle FINALLY seems to be back to normal! The ignition coil was replaced under the lifetime warranty from Advance Auto. There was only 23,457 miles on that coil and plug when the idle started acting up. That's disappointing since the original OEM coils were in the car for 138,253 miles and I replaced them when the car was having the infamous hard starting in cold weather and the problem ended up being that AC amplifier module that is behind the radio. I should not have tossed those OEM coils! Dumb!

Anyway, if your car is not idling correctly after cleaning the throttle body and doing the idle air volume learning and throttle position closed procedure, cleaning the MAF, and checking for vacuum leaks, I would suggest taking the car to a trustworthy shop to have a scanner plugged in to collect data and have it all reviewed. The data showed that Cylinder #5 was performing well enough to not set the misfire code but bad enough that it didn't compare well to the other cylinders.

Oh, one more thing, when you don't replace ignition coils and plugs frequently, it can take a while to remove enough "stuff" to get the coil out. In a Murphy's law sort of thing, Coil #5 is on the passenger side of the engine back at the fire wall so there isn't a lot of room to work there. It took me 2 hours to get the coil and plug out and the new one installed. If it had been Coil #2 on the front of the engine on the driver's side, it might have taken a total of only 20 or 30 minutes.

I will report back after a weekend of driving.
 

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Discussion Starter · #12 ·
It is now Oct. 27, 2021 and all is well with the 2007 FX35. No more idle issues after replacing the ignition coil/module and spark plug on Cylinder #5. I'm really disappointed that this malfunctioning ignition coil and plug were not consistently setting a misfire code. It happened only once after I had liberally sprayed throttle body cleaner at the butterfly. Oh well.

If it wasn't for the shop saying that they saw #5 wasn't the same as the others when the data screens were reviewed from the scan tool, I would still be trying to figure this out.
 
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