Revs hanging

[BusaSteve]

Hi guys.

I did a comprhensive search but could only find surging problems relating to turbo diesels, blanking off the ERG and also fiddling with the SCV.

The problem with my 07 MM 2.4 petrol manual is the rpms seem to hang between gear changes. Its not overley serious and it only happens for a very short time....ie about two or three seconds but it is annoying the crap out of me. I looked under the bonnet and there appaers to be a valve with white striped and a yellow striped hoses....as pictured in one post about a diesel and I am assuming it is the SVC. I will block this off as explained to see what happens....my point is are there any members here that have had the same problem on a 2.4 petrol engined truck? and if so what did you do to sort it.


Thanks in advance


Steve

[sierra]

If it's a cable operated throttle I would be checking the return spring is alright and oiling the cable and linkages.

[BusaSteve]

Ahh yeah Sierra thanks I shoulda said I already lubed the cable and the return is fine...nice and strong and no sign of sticking. One thing... it appears to be only while on the move and at about two to three k rpms...the rpms drop fine when stationary....wondered if there is a speed sensor of some kind?


Thanks for any reply's

[sierra]

It's not in the pedal? In case you were blipping it at the engine?
Sometimes when you get a weird problem it's worth going to the Mits dealer and asking the service advisor. They must have come across it before and could put you on the right track, if you get a bright one.
I would say something in the emission control sounds likely to be the culprit.

[Kegsy]

It sounds like the throttle cracker in the ECU.

Have you just got this vehicle? Or have you driven it for a while and its just started doing it?

[hvac guy]

Sounds like the adjustment screw for the emissions control.
It holds the throttle on for a bit when U take your foot off the pedal
U may have a vacuum hose off as well have a listen for a hissing noise near the motors intake system
And check the pcv on the tappit cover it should only operate at idle.

[BusaSteve]

Ok Kegsy...throttle cracker? not sure what this is and if it is ecu related am unable to do anything about it. I just bought the truck three weeks ago and I don't want to take it back to the stealer as they will fart me around for a couple of hours and then tell me they couldn't find a thing wrong.

hvac guy....I really should totally remove the throttle cable and lube it overnight and also check the pedal but the problem doesn't seem to be apparant when out of gear and idling in the garage the revs drop cleanly and almost immmediatly when I operate the pedal or cable from under the bonnet. As for the emmissions control screw not too sure where that is but will take a look see and report ditto the hose but I did a quick check of hoses and found none loose or off....pcv will get a good look too. Thanks for the suggestions guys will repost when I find out what it is.

[Kegsy]

Ok Kegsy...throttle cracker? not sure what this is and if it is ecu related am unable to do anything about it. I just bought the truck three weeks ago and I don't want to take it back to the stealer as they will fart me around for a couple of hours and then tell me they couldn't find a thing wrong.

Ok since you're new to the vehicle and are unaware of how it should drive when its 100%, Im going to go on a limb and say its completely normal. But please get it checked, but my money is on 'its completely fine sir'.

Lots of cars incorporate a "throttle cracker" & "follower" into the ECU programming.

Without going into a whole story, its meant to do it.

It allows a little extra fuel and air to come in after you let up on the throttle to activate the emissions control like hvac guy has hinted at. Often it helps put extra heat into the cat converter extra to assist in reducing emissions, or suck air through various pollution gear.

Previous generation Suzi Swifts are notorious for having a massive throttle crack in the ECU.

Normally its just a change in driving style required to get a smoother drive.

If you google "throttle cracker and follower" there's probably a heap of info. Probably a lot to do with tuning of a car, but it may help you understand the concept and maybe help to see if you think its within a fine limit or excessive.

[BusaSteve]

I thought I'd replied to your post Kegsy but can't find it so I will post again. Thanks for that I went and googled throtttle cracker and there are heaps of posts about them. I had never heard about them but given everything is controlled by chip now its hardly surprising. I will still remove the cable and lube it up and also the pedal pivot to see if that helps but other than the revs hanging for half an hour will just have to leave it as it is...you are probably right that it is how it should be and I have never come across it or noticed it as much. Thanks for all the replies guys.

[sierra]

I drove a new ML single cab manual with the 2.4 petrol engine before I got the current diesel version and there was no problem with the throttle feeling delayed/staying open. In fact I was impressed at the time, just how smooth and flexible the engine was, around town anyway. I felt the gearbox wasn't as good as the diesel one but that was all.

It might be a function of the cold start that is failing to turn off when it warms up? If it's very cold my diesel does it but it stops within 30 secs or so.

[BusaSteve]

Yeah it does rev a little when cold ...I will lube the cable and pedal pivot to see if it helps. I guess the cold start fuction is now ECU controlled will have to searh to see if I can find the air temp module....maybe spray some of that 'fix everything' WD40 around hey?

Will post up what happens but am riding the mighty Busa this Sun ...prepping it Sat... so might not get around to it till mid week....will let you all know what I find.

[Chill]

I have the ML 2.4 petrol and it does the same thing. I always wondered if it was normal or not. I test drove an MN 2.4 petrol but it wasn't as bad.

[BusaSteve]

I havn't had a chance to look at the cable or anything else for that matter but I got to thinking about the throttle cracker that Kegsy told me about. Anyone know if it is controlled by the injectors staying open longer or a mechanical device operating the throttle butterfly. If its the latter I should be able to (a) find it and (b) fart around with it a bit. From what I read it seems unlikely to be this type of device as many either reflash the ECU or diddle around with the settings....do tell me it is a vacuum operated or similar device guys!!

[hvac guy]

Take a photo of the throttle body and put it up.
Will see it if its there.
That's if its vacuum operated

[BusaSteve]

Thanks for the offer hvac....I took some bits off today and cleaned them...the MAF?...located on the air intake...after the filter. A device from the inlet manifold....don't know what it is and another device....had three pipes one from a vacuum pot to provide vacuum and two others red trace and white trace going to an electrical vacuum operated switching device. There is a vacuum device just below the butterfly that I didn't bother with. Now before everyone flames me for piss poor explanations I did spray some WD40 on the accelerator return spring and pivot...and either one of the gizzmo's I cleaned did it or the lube job on the pedal did but it seems much better....revs drop faster now....so who knows or cares? lol!

[sierra]

Good to get a result.
I hate having any throttle delay.

[BusaSteve]

You would think that wouldn't you ...but now the engine check light has come on and cold idle is non existent... about three rpm I think almost stalls if you don't goose the throttle... and warm idle is twelve hundred...too high. Time to take it to Mits and see what they say....will keep you guys posted.

[Homer]

Have a look at your maff wire connection mate...possibly an issue there. I have the same symptoms if I disconnect mine...

[BusaSteve]

I tried disconnecting and reconnecting the MAF but it had no result...I took it to Mitsubishi and they have told me it is the air flow meter...their words and I am assuming they mean the MAF...so that would explain doing what I did having no effect.

Three days for the part to get here and have it fitted...pretty duff I thought... pissant part and a two minute job to fit it taking three days. Engines are getting too comlex with electronic control of so many parameters that dealers cannot possibly carry all of what appear to be pretty delicate devices...think I'll sell the Mits and get a 1970's Ford with a carb...lol!!