Strange Engine Idling

iceman153 [OP] · 11-20-2012, 01:08 PM

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!

**Smalldog** · 11-20-2012, 01:22 PM

Thermostat? Does your temp gauge look good?

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**cnckart** · 11-20-2012, 01:23 PM

If you have it on defrost it also runs the AC compressor, that could cause an idle fluctuation.

iceman153 [OP] · 11-20-2012, 02:00 PM

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!

**Smalldog** · 11-20-2012, 02:27 PM

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..

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iceman153 [OP] · 11-20-2012, 03:22 PM

Actually no, I have a MT... It is a little strange, but does seem to stop when she's fully warmed up. I guess I'll have to drive her some more and see if it happens at any other times. Any comments on the engine noises?

Winterpeg · 11-20-2012, 03:27 PM

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.

Give her some love too... change the plugs, filters, oil, clean MAF and throttle body.

iceman153 [OP] · 11-20-2012, 04:09 PM

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.

Tofu · 11-20-2012, 05:14 PM

Beside the ac compressor clutch it could also be the cooling fan.

**Smalldog** · 11-20-2012, 05:29 PM

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.

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