RPMs too low

1.8-liter VVTL-i (2ZZ-GE) and VVT-i (1ZZ-FE) engine, transmission, exhaust, intake, and performance tuning discussions
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Caretaker

RPMs too low

Post by Caretaker »

I've posted about this before, but have received no answers. So here we go again in hopes of a solution. For the past year+ my RMPs dive down to 600 when coming to a complete stop at stop signs/lights. The car never stalls and does recover to 750 RPMs after the engine shivers for a second. I have had just about every idle part cleaned of carbon, and still the problem persists. The car has new Denso plugs, which did not solve the problem either. Original coil packs, and original PCV and intake manifold gasket. I resurrect this topic because I just ran into someone at the gym who has the 2.4 liter Vibe. She said her's began doing the same thing recently at 55,000 miles. Mine, with the Corolla engine has 95,000 miles. So, two different engines, which to me means that the PCV and/or intake manifold gasket can not be the problem since they are totally different engines/parts. Can anyone else on this board chime in if they also have this problem so I can try to narrow down the common element between the two different Vibe engines in hopes of solving my problem?
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vibrologist
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Re: RPMs too low

Post by vibrologist »

My best guess is there is an issue with the idle air control valve. I would clean the throttle body and the Idle air control valve.

We used to have a '98 mazda protege in our family and it did the same thing. It got better with every cleaning job I did, starting with the egr valve. But it really improved when I cleaned the throttle body and the IAC valve that was attached to it.
Vibrologist
'05 Vibe

"It is important to know the difference between 'accurate' and 'precise' even if you are neither!"

viewtopic.php?f=30&t=43476
lannvouivre
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Location: Texas yay

Re: RPMs too low

Post by lannvouivre »

I would clean the throttle body (the 2nd gen you own will be drive by wire and not have an IAC) first, then use some carb cleaner to look for a vacuum leak with the engine running. It sounds like you're getting issues with the wrong fuel/air mixture. It's probably going to be a vacuum leak, but when I had a bad ground on my fuel motor circuit control relay, I had similar issues. With the electronic controls on modern cars, though, it's more likely to be vacuum unless there's a wire problem (vs carburetted cars that can have excess fuel delivery or incorrect ignition timing).

You probably already know the usual suspect areas, but it will be somewhere on the intake side or on the EVAP emissions system.

You can also hook up a scanner and look at your O2 sensor readings. I can look on mine and give you numbers for what they should look like.
"If you don't love me at my diddliest, you don't deserve me at my doodliest." - User ktluvscricket of reddit
Caretaker

Re: RPMs too low

Post by Caretaker »

Thanks for both of those replies. I will bring it up with my mechanic. Here's one other piece of information. It DOES NOT happen all the time. It most likely happens when the engine is fully warmed up and has been operating for awhile. When it starts to happen (nearly every day), once it happens, it will happen at the next stop sign and the next and the next and the next. So I wanted to put out that piece of information about the irregularity of when it happens. As such, wouldn't a vacuum leak make the diving RPM situation happen ALL the time?

Also: does anyone have a recommended, active Matrix board I can post on to (or someone who can post my original message for me), so that I can see if anyone on the Toyota side has experienced this condition?
jayoldschool
Posts: 294
Joined: Mon Aug 04, 2014 6:04 pm

Re: RPMs too low

Post by jayoldschool »

Matrixowners.com (about as active as here)

Toyotanation.com

FWIW, my 04 1ZZ manual trans behaves similarly...
thebarber
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Location: kitchener, ontario

Re: RPMs too low

Post by thebarber »

IACV
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lannvouivre
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Location: Texas yay

Re: RPMs too low

Post by lannvouivre »

thebarber wrote:IACV
Yeah, to jay: Clean your IACV. If that doesn't clear it up, and you verify there's no vacuum leak, you will need a new IACV. Zane had this issue for ages on his 2ZZ and had to replace it to solve it.
"If you don't love me at my diddliest, you don't deserve me at my doodliest." - User ktluvscricket of reddit
jayoldschool
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Re: RPMs too low

Post by jayoldschool »

Thanks, guys, I'll look for a how-to (and check Mitchell).
jolt
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Location: Twin Cities, Minnesota

Re: RPMs too low

Post by jolt »

Here is a "How to" on this board with pictures for cleaning.
viewtopic.php?f=17&t=36489&p=476353&hilit=IACV#p476353

And here is a link for the opposite problem of high idle speed. You can see what fixed that in the end, just of interest and for knowledge down the road.
viewtopic.php?f=20&t=44637&p=507583&hilit=IACV#p507583
gtv237
Posts: 387
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Re: RPMs too low

Post by gtv237 »

I've struggled with intermittent rough low idle as well. What's happening is the computer is adapting to different conditions. Plus Toyota presets these motors to run pretty slow from the factory. You can preload the motor mounts a bit. This will turn a 'bucking' low idle into a slight vibration. It makes a significant difference but it may reduce the mounts lifespan. Or you can disconnect the battery for a while to reset the computer and hope it gets it right this time. Be sure to leave the headlights on or something to help drain out any capacitors.

If all else fails you can manually adjust the idle set screw. I would only do this as a last resort. Too much adjustment will cause the PCM to throw a code.
rogue1313
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Joined: Sun Jan 13, 2013 5:29 am

Re: RPMs too low

Post by rogue1313 »

Did you ever figure out what the problem was?


I have a 2010 Vibe with the 2.4 engine....77k miles.....and it's doing the same thing.

Occasionally, not very often, when I come to a stop, the RPMs will drop to around 500, the engine will run rough, and I'll get a pretty good vibration/shake.....it acts as if it might die, but it doesn't.

If I give it gas, the RPMs go up and it runs fine. Sometimes it will drop back down to 500 and run rough......sometimes it'll will stay up at the 700/800 RPM range and run smooth.

It might do that for a couple/few stop signs in a row, but generally it goes away after a few more miles of driving. Other than that, it runs smooth while I'm driving down the road.

I've noticed it on & off for the past year or so.....but it's so infrequent, I basically forget about it after it corrects itself.

As part of my maintenance routine, I decided to change the coils last summer, with AC Delco parts. I changed the spark plugs too....as well as the air filter. I haven't driven it more than 8k miles since then. I changed the battery a few years ago when I bought the car and haven't disconnected it for anything since. I usually run some Chevron Techron fuel additive through it every couple of months as well.

It's strange.....99% of the time, doesn't do it. Usually only does it after I've been driving for a while.....so it's not a cold issue.....and I live in Southern California, so it never gets really cold anyway.

Can't be an engine mounts causing vibration, because that wouldn't cause the RPMs to drop.

I'm thinking maybe the Idle Air Control Valve (or equivalent, whatever is on this engine)?

Any help/ideas would be greatly appreciated.

Thanks.
postmac
Posts: 6
Joined: Fri Aug 13, 2010 12:17 am

Re: RPMs too low

Post by postmac »

my 06 vibe base starts rough and low idle at stoplights. Mechanic said there was low compression in cylinder 3 and when doing compression test with compressed air heard air coming from exhaust pipe (was getting cyl 3 misfire engine code). He said exhaust valve not functioning properly. 2K to rebuild it or 2k to replace engine...
Been running on 3 cylinders for a year now and will drive that engine till it dies.
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