Double revving

[Jon S]

I don't really know how to explain this other than saying that if I blip the throttle I get a double rev. Ie a quick on and off leads to a rise in revs, a pause then another rise in revs before falling back to tick over ( both rises are after I have released the pedal). The engine was fairly cold and I haven't used it for a while and maybe it's always done it and I've never noticed. Does anyone else recognise this or have an idea what may be causing it?
The on,y mod is a cat free manifold (toyosport I think)
Thanks for the advice

[jonbill]

After the first rise, does it return to idle or stay where it is?
I.e.
Throttle/release...revs rise to 2k...pause... Revs rise to 3k... Revs return to idle or
Throttle/release... Revs rise to 2k...return to idle... Pause...rise to 2k...return to idle

Or something else?

[Jon S]

The first one

[Ardent]

hello Jon S

The bit that sticks out for me is the "The engine was fairly cold"
Given the amunt of coolant to warm up (9 Litres)ish, may I propose, you let things come up to temp, repeat your blip test and report your findings.

These cars can take a bit longer to wam up than your average motor.

[shnazzle]

Thing that stands out to me a bit is "haven't used it in a while".
I'm with Ardent. Give a run for a bit and let all the juices course through her veins properly again.

[Jon S]

Ok will do. I'll let you know how it pans out


Sent from my iPhone using Tapatalk

[Jon S]

Ok will do. I'll let you know how it pans out


Sent from my iPhone using Tapatalk

Ok I got it up to temp and it still does it though perhaps not quite as obvious. There is a bit of delay before the revs rise at all, my foot is right off the pedal before the revs rise( is this normal?) I'll try and add a video - a picture says a thousand words and all that!


Sent from my iPhone using Tapatalk

[Jon S]

Hmm I don't seem to be able to upload video from my phone. Is my description enough?


Sent from my iPhone using Tapatalk

[delhusband]

Hmm I don't seem to be able to upload video from my phone. Is my description enough?


Sent from my iPhone using Tapatalk

Video too big to upload here, but you could upload to YouTube, and then add a link

[jonbill]

Is the 2nd rev rise a small one?
IME the ecu does lift the revs a little  briefly as you lift off. People notice it at gear changes.

[shnazzle]

Ok will do. I'll let you know how it pans out


Sent from my iPhone using Tapatalk

Ok I got it up to temp and it still does it though perhaps not quite as obvious. There is a bit of delay before the revs rise at all, my foot is right off the pedal before the revs rise( is this normal?) I'll try and add a video - a picture says a thousand words and all that!


Sent from my iPhone using Tapatalk

Oddly Helen's car does this when cold but goes away quickly once a bit warm.
Only since the standalone went on, so maybe it's a sensor thing.
Eager to see the solution to your issue.
I do know for a fact that a similar effect happens if you unlplug the throttle position sensor. You get a delay on throttlw

[Jon S]

I might have to get my teenager to show me how to upload to you tube if I can drag him away from his PlayStation for long enough! If others have a slight rise after liftoff then maybe it's that I've only just noticed it.
It's only a few revs eg if I blip quickly it will go to 1600 then 1800 before dropping back to tick over.
Is the throttle position sensor an easy thing to get to? Just wondering if a wiggle on the connection and a squirt of cleaner could help.



Sent from my iPhone using Tapatalk

[Jon S]

Well I've finally worked out how to use YouTube. So here is one of the dullest videos you'll ever see but it will explain it better than I can.
5B7CE9A3 D01B 4071 8CCA CB25EC0E792B
I hope this works!
Jon



Sent from my iPhone using Tapatalk

Edit: link = https://youtu.be/PamoQOncoCM

[Ardent]

Copied and pasted into youtube
but not sure I am any the wiser.

[shnazzle]

I'm going to try this in mine tomorrow.
One thing I did notice is how long it takes to rev once the throttle was stabbed.
People with stock mr2s; is this normal?

There were only two instances in that video where I saw the double-rev which to me seemed like a normal response to a very quick stab at the throttle.

The TPS is very easy to get to check the plug.
Left side of thr engine, far back, under where the intake pipe goes into the throttle body. There's a visible plug. Unplug it and try again. Should be the same effect but much more exaggerated.

[jonbill]

I'm not really seeing anything unusual....

[Nvy]

An idea, what if something is stopping the free movement of the throttle body plate? I rly dont know how these are made but id assume that they have some kind of bushes where the moving part is. I have had something like this in my clutch pedal when the little plastic thingy was broke so half of the movement would be metal to plastic and half metal to metal.

P.S. Just an idea, i havent seen throttle body in my hand. My revs go straight up, no stopping.

[Jon S]

sounds like checking the TPS would be a good move so I'll have a look at this.
Thanks for all the advice. I'll let you know.

[shnazzle]

Here's mine on a cold start.
It revs instantly on stab and then drops quickly until it hits the airflow point of the idle air control valve

https://youtu.be/dSy7JfuGVUM

[shnazzle]

And on warm.
Take into account that my warm idle is a bit rough with my current exhaust and o2 sensor issues

All in all, I don't think you have too much to worry about.
Potentially you have a sticky idle air control valve from being sat doing nothing. I know from bitter experience that they don't like that.

So basically all is working as it should but your IACV is a bit retarded.

Rev, IACV closes and car revs as normal
Release throttle, IACV gets signal to open, revs drop, then IACV opens after unexpected delay and feeds a tiny bit of extra air in. Revs increase a tiny bit again showing that "bounce". Revs drop again and IACV now open and all is normal

https://youtu.be/aPc8j6PwfiE

[Jon S]

Thanks schanzzle that's really encouraging. Is the IACV something I can take out and clean or oil? (If so where is it - sorry for being a bit dumb).
Or is it an easy (cheap!) thing to replace?
Thanks for your help.
Jon

[Carolyn]

There's a 'how to' for that:

https://www.mr2roc.org/forum/index.php?topic=60448.0

[shnazzle]

Personally I'd opt for a couple of cans of EGR cleaner through your intake (at the airbox) to see if that frees up the IACV. Costs 10 quid and 15 mins.

It's certainly not the easiest job. It's fiddly.
But do it slowly and procedurally and you can't really go wrong.
Worst case scenario is you pee coolant all over the shop by forgetting to clamp the two little hoses that go into the IACV. I've done this once, a clamp came loose. Not fun.

Taking the IACV off the throttle body requires removing three screws that seem to have been threadlocked in place, and are very soft metal.
Top tip; start with the two parellel screws. Because if the one screw at the end won't come loose but those two are undone, you can actually twist the IACV off to free the screw. Saved me once.

[Jon S]

I'll try the squirting EGR cleaner into it first and see if this does the trick, my mechanical abilities are somewhat limited so it sounds like taking the valve off might be one for a mechanic who knows what he is doing.
Re the squirting- would you take the airbox (and I presume the MAF) off to squirt or just take the filter out?

[shnazzle]

The simplest way is to unscrew the MAF and spray it down the hole.
The engine will like to stall though so you'll need to rev it a fair bit by manually pulling the throttle cable while spraying.
I usually end up having to restart the car a good 5 times at least