Strange rpm behaviour when releasing the accelerator pedal

[mirelay]

Hello,

I have a Volvo S60 2001 with the petrol B5244S2 engine and manual transmission. It is has the throttle repaired by some German company Actronics and has the Sacer module in it (done by some previous owners).

I have observed the following:
First, it has a rev hang, but I've read that this is common for these ETMs.

Second, when I drive and release the throttle pedal and I move to neutral, the rpms does not fall completely to idle, but fall an hang at somewhere around 1200 for 1-2 seconds, then continue to 1000, where a shorter hang can be noticed. Then the fall to (I suppose 750) idle.
This also happens when I stay at a traffic light and decide to rev to say 3000 rpm and release the gas pedal.

Sometimes, when I decelerate to stop, the RPM hang under the normal 750, but I rarely observe that, after I changed my serpentine belt, tensioner and alternator freewheel.

If it is a vacuum leak, where should I look at?

I will be happy for your advice.

[AndyV7o]

It might just be anti-stall measures due to a very lean mixture because of emissions etc...

[oragex]

Being the non turbo it is fairly easily to clean the throttle body flap with a piece of lint free cloth, just undo the large hose at the tb then flip the flap open and clean both sides all around all surfaces. But it may also be an issue with the throttle body itself.

[Georgeandkira]

Regarding cleaning the ETM on a non-turbo.

Is it OK to move it by hand or should it be opened and closed by moving the accelerator pedal?

I don't want to strip any gears or damage any small motors.

[Clan]

Originally Posted by Georgeandkira

Regarding cleaning the ETM on a non-turbo.

Is it OK to move it by hand or should it be opened and closed by moving the accelerator pedal?

I don't want to strip any gears or damage any small motors.

You won't be able to cause any damage it is an extremely robust device , direct drive with no gears at all … ( Unlike the later ones which do have gears that can strip )

[mirelay]

Originally Posted by oragex

Being the non turbo it is fairly easily to clean the throttle body flap with a piece of lint free cloth, just undo the large hose at the tb then flip the flap open and clean both sides all around all surfaces. But it may also be an issue with the throttle body itself.

I cleaned it once some time after I bought the car, but just from one side, without removing the throttle body. It was very clean any way (I've seen pictures of very bad throttles). Yesterday, just before posting, I removed it from the car an cleaned it from both sides, and payed attention to the hinges. It still ran the same.

[ASt85]

Originally Posted by mirelay

Yesterday, just before posting, I removed it from the car an cleaned it from both sides, and payed attention to the hinges. It still ran the same.

Did you re-use the gasket or replace it when you re-fitted the ETM? Apparently re-used ones tend to leak, which can cause problems.

When the ETM is removed the ECU "re-learns" how it is performing so will initially run the same way that it was. When the system has fully updated it should alter how it is idling and the "hanging" should stop.

There's a how to for the 850 series at the link below, but the same process works for most Volvos/cars & other similarly controlled cars/vans & etc.

http://www.volvotips.com/index.php/8...rn-procedures/

The exact procedure differs a little depending upon year of manufacture and model but the key is to let it idle for 5 or 10 minutes BEFORE you start driving it after doing anything with the throttle body.

It might be better to restart the process by either disconnecting the battery if you have the radio code, and carrying out a cold reset - battery disconnected for in excess of 15 minutes - short +ve and -ve battery leads/clamps, which makes sure that the memory is dumped. Reconnect the battery having turned the ignition key to positionII to prevent the airbags firing or you could try pulling the ecu fuse for ten minutes if you don't want to mess about disconnecting the battery.

When you've got everything turned off - including the lights, if you have DLRs put the light switch to the sidelight position start the car and let it idle for at least ten minutes in neutral with the hand brake off. If yours is an auto, then turn off the engine after those ten minutes and put it in drive with the wheels chocked so it can't roll forward, again letting it idle for ten minutes with the handbrake off. Apparently keeping the hand brake off means no warning light so the only current drain is from the various sensors/ecu/cem which makes it re-learn more quickly.

The process also works if you ever replace lambda sensors etc.

[mirelay]

Thank you for the details.
Yes, I had a new gasket, so I put it after the clean.
I will try the reset process.
I tried this, which I read on some Volvo forums:
Ignition to position 2 and then press all the way and release (both directions slowly) the throttle pedal twice, but this doesn't help.

Yesterday I also removed the MAP and tried to clean it with MAF cleaner. Some time ago my MAP hose was off, I found that the car will stall behave very bad if you manage to keep it in revs. (I wasn't intentional, I didn't know what the problem was at that time)

[Clan]

Originally Posted by mirelay

Thank you for the details.
Yes, I had a new gasket, so I put it after the clean.
I will try the reset process.
I tried this, which I read on some Volvo forums:
Ignition to position 2 and then press all the way and release (both directions slowly) the throttle pedal twice, but this doesn't help.

Yesterday I also removed the MAP and tried to clean it with MAF cleaner. Some time ago my MAP hose was off, I found that the car will stall behave very bad if you manage to keep it in revs. (I wasn't intentional, I didn't know what the problem was at that time)

Your " problem" is normal after a new throttle or repair ., you have to drive the car around, do some idling too , switch off .. you might have to do this twice , That should re adapt the throttle , When you turn off, the system learns the new figures , so try it a few times.

[mirelay]

I started to suspect the break booster, so tried multiple break pushes when the car is stopped and at idle. See the video: https://www.youtube.com/watch?v=3VPww6iYQyI