Toyota FJ Cruiser Forum banner

Strange Engine Idling

22K views 38 replies 17 participants last post by  discoganya 
#1 ·
Hey Guys,

I just bought an 07 FJ, absolutely love her so far, but I've noticed that it's constantly changing idle speeds every 10 seconds cycle between 1k RPM and about 900 RPM. It's not idling rough, it'll just go 900 for 10 seconds, then 1000, then 900 etc... I noticed that the cooling fan is also constantly running, even at cold start, so it's not that turning on/off. Any idea's on what it could be? Almost seems like a relay or something kicking in putting extra load on the alternator?

Thanks!
 
#2 ·
Thermostat? Does your temp gauge look good?


Sent from my iPhone using AutoGuide.com App
 
#4 ·
Wow, fast replies, you guys rock :) So I just went down and listened for a while, I didn't quite get the symptoms right, and it's probably not an issue (only had her 2 days now!). So on first cold start, it'll idle at 1100, then slowly go down to about 750, then almost immediately I hear a relay click in the engine bay, and it jumps up to 1,000 and slowly comes back down to 750. It keeps doing that cycle (click, 1000 -> 750) for a while and eventually settles down and stops, warm idle is 700. The temp guage shows just a touch below halfway between hot and cold, which seems normal. But as once she fully warms up it calms down i'm guessing this is just the normal warm up procedure and I got ahead of myself thinking it was an issue :) Just felt strange hearing it bounce up and down like that

The engine idles pretty smooth, but it's quite loud, definitely has way more lifter type clicking/tapping noise going on than i'm used to, not sure if that's normal for these engines or not. Nothing I can hear from inside the car, but it's very noticeable just standing next to the truck with the hood closed. I did check the emissions unit that people have said makes a click and it's not that (I disconnected it). Does this seem normal to you guys? I might take off the engine cover and poke around with a stethoscope later when I get time.

Thanks!
 
#5 ·
Both brad and I have MTs, and I assume you have an AT? Maybe that is normal with the AT. We need an ATer to chime in. I don't think it should fluctuate back and forth on the rpms. Starting higher and dropping is normal but not getting high again, etc and on and on..


Sent from my iPhone using AutoGuide.com App
 
#7 ·
x2 on the question whether it's on Defrost, defrost/feet mix, or a/c.

All of the above will cycle the a/c system and cause power fluctuations as it kicks in. This can also cause the notorious "bump" feeling at a stop light if you don't have your foot on the brakes hard enough.

:cheers:

Give her some love too... change the plugs, filters, oil, clean MAF and throttle body.
 
#8 ·
Sorry, i missed the defrost q, I don't think it was on defrost, or had the AC on, but I'm not sure, and it did sound an awful lot like AC compressor turning on. I'll check it next time, good call.

Definitely going to be giving her some lovin this weekend, i'll probably do all of your suggestions, as well as tracking down the source of the ticking.
 
#10 ·
When warmed up, my MT idles at 700 RPM in neutral. If I turn on the AC it idles at 800 RPM. It never fluctuates in either of the modes above. I think it's the fact that your fan is always on..or whatever is causing it to be on.


Sent from my iPhone using AutoGuide.com App
 
#11 ·
The fan on the FJ is an engine driven fan. It does not click on/off.

X2 on the HVAC being set to A/C or Defrost / or MAX cold/Vent setting.

DEWFPO
 
#12 · (Edited)
Maybe check your battery. If it's a stock Panasonic they have a window on to of the battery that gives its status. Check that when the engine is running. Mine had a funny idle a few times in the past 165K miles. When my alternator fried, when my battry died and when I put in a new battery and was resetting the ECU.

*check the cheap stuff first

I just recalled another time when it idled funny. I was 35,000 miles overdue for new spark plugs and they were toast.
When is the last time those were looked at?


PLUS- I believe I sold three FJ's this evening at the Taco place. 9-Ball caused quite the stir!
 
#13 ·
It does have the stock panasonic, i'll have a look for that status window next time I take her out. I didn't see any evidence in the maintenance history the plugs were done, but it could have been done DIY. Either way i'll give her new plugs/oil/filters and clean the MAF this weekend and see what happens. Thanks for all the suggestions guys, i'll post what I find. I have the option to get a third party warranty through the toyota dealer I bought her from, but looking at all the exclusions and red tape I think it'd be like winning the lottery getting any money out of them for repairs.

On another note, I can't wait to take her out on some trails :)

Mark
 
#16 ·
Even if your a/c is off, if you have the air temp dial cranked all the way hot or cold it will activate the a/c. Try moving air mixture to not max hot or cold, and see if that helps.
 
#25 ·
That's the one quirk I hate about the FJ's A/C controls. By the way, I've never had the compressor go on at the full hot setting. If you turn the temp knob all the way to cold and not pay attention while doing it, it will turn on the A/C compressor. The only indications are that you start getting cold air, the idle changes up and down and the A/C light goes on behind the A/C button. I have to be careful to stop turning the knob one notch before full cold if I don't want the compressor on. If I accidentally go too far, I have to turn it back a notch, then push off the A/C button. How many times I've done that drives me crazy. My husband's done the same thing. Whoever designed that should be hung out to dry in a sandstorm.
 
#17 ·
Yeah i had the fan completely off with the temp set in the middle, its really puzzling as to what is doing this. it's definitely far less frequent after the engine has warmed up, and i do hear a loud click noise from in the engine bay when the rev's jump up to 1k, so something is engaging. Can't hear it from the cabin. Any other ideas guys?

Note if it is the thermostat would i be able to see the temp guage move up and down, or would the needle be obviously towards the cold side? Or can you really only know with a code reader?
 
#18 ·
It should never idle at 1,000 rpm when hot, even with a load on it. When my compressor comes on, you can barely see the tach needle move. I'm trying to figure out what in the world would put a temporary load on the engine, have a relay (the click you hear) and cause the idle speed to go up to 1000 rpm's.

Do you have any aftermarket accessories (like heated seats)?

Are you still under warranty? Have you taken it to the dealer?

It is certainly not normal.

DEWFPO
 
#20 ·
I've changed out the spark plugs, that made no difference (I wasn't really expecting it to). The alternator is an interesting one, it does produce good charge at the moment, would there be any signs in terms of voltage loss if the alternator was causing it? Anyway to debug the alternator theory?

The car does have a pretty intense audio system from the previous owner. It had a ridiculous sub box that took up the entire trunk, I've ripped that out and replaced it with a single small sub mounted in the stock location. The system has a dedicated breaker switch, when I trip the breaker it makes no difference to the idling.
 
#21 ·
Forgot to mention I also cleaned the MAF with MAF Cleaner, also nothing. Also note I may have miscommunicated, but when hot it does happen every once in a while, nowhere near as often as when cold, and the RPM only goes up to ~850-900

Thanks for all the help and suggestions guys.
 
#24 ·
Nope, I've just been ignoring it. A little update tho, my alternator has since failed, replaced it with a new one. As i'd just been ignoring this for so long I don't actually remember if it's still happening, lol! Traveling at the moment, i'll try and remember to pay attention when i get back and see if it's still happening.
 
#23 ·
Hey guys I have a 2011 AT that does something similar to this. It did it since day 1 (I bought it new) so it never really bothered me, figured it was just Toyota and all the fancy electronics doing stuff. With my Ultraguage I see the throttle position hover anywhere from 14.7 to 16.5. Even with the AC off it will go between 14.7 and 15.3. I don't really notice much of a difference in RPMs (maybe plus or minus 50) or hear any clicking, but I do see the throttle go up and down.

One trend I noticed, slight tangent here, but when I come off the highway and come to a stop the engine temp goes up from 185 to 192, and at this point the throttle also goes up, at which point the engine cools down. So I kind of just figured that the electronics were intentionally adjusting the throttle to keep everything happy.

$0.02
 
#26 ·
Yeah, It doesn't turn on at max heat, only max cold, definitely very frustrating, totally unintuitive... Definitely not the cause of the issue here tho, I'll let you guys know if the alternator replacement fixed the problem. If it didn't i'm out of ideas, I've just been ignoring it, but I would love to get to the bottom of it!
 
#27 ·
iceman153, you might want to read through this PDF. It tells what components work together to control idle speed on a 2007 FJ. Maybe something going on with one of these parts is causing your idle issue, like a slightly sticking throttle actuator, or maybe the accelerator pedal position sensor is sending out a dirty signal to the ECM when it's not being pressed. I assume you've checked for little vacuum leaks.

http://purefjcruiser.com/docs/2007 ... Engine Control System/SFI System/0050041.pdf
 
#28 ·
I actually haven't checked any of those, and I probably should when i get back, but I feel like the pattern is too rhythmic for is to be anything in the throttle/idling. It definitely presents like something is being turned on/off every 10 seconds or so, you can distinctly hear a relay engaging/disengaging. Possibly something in the cooling system? The fan is mechanical and always on, but is there anything else in there that might be getting cycled on/off due to a bad sensor or something?
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top