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Hesitation when accelerating
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Old 17 Aug 2009, 11:56 AM   #1 (permalink)
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Hesitation when accelerating

I know this topic pops up all the time and theres a list of possible causes, but Ive tried almost everything I can without putting money out. But havnt quite fixed it.

I bought myself a 2000 W reg Impreza Turbo nearly 2 weeks ago, its was running quite badly when I got it but now its 99% perfect.

However it just feels a little hesitating sometimes when accelerating. Worst on early cold mornings. I always let temp get up before I go over 3k but even below that and once warm it can be a little hesitating.

Things I have done:
Check all boost pipes (tiny hole found in actuator made a massive difference once replaced!)
Cleaned Boost solenoid
Clean MAF
Cleaned Intercooler
Oil and all filters changed
Changed all Plugs
Hand vehicle diagnostic check - all clear

I cant think or or havnt seen anything else on here it could be so guessing its either a faulty MAF or lambda sensor? But need to find a way to test them, as I dont want to shell out for new ones If theres nothing really wrong with the old ones.

Any suggestions anyone has please help, its quite a minute hesitation since I found the hole in the actuator, but it is still something I would like to get sorted.

Thanks Robb
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Old 17 Aug 2009, 12:56 PM   #2 (permalink)
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Re: Hesitation when accelerating

Hi Robb.

Unplug the MAF sensor at normal operating temperature. If the engine keeps on running then the MAF is faulty.

Did you do a ECU reset?

If not .... Link: ECU Reset... How many different methods are there???
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Old 17 Aug 2009, 01:03 PM   #3 (permalink)
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Re: Hesitation when accelerating

Ive had the ECU unplugged for quite a while before today, but I will go unplugg my battery for an hour or so now and see if that makes and difference.

I will also test the MAF
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Old 17 Aug 2009, 01:07 PM   #4 (permalink)
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Re: Hesitation when accelerating

Quote:
Originally Posted by dougie175 View Post
Ive had the ECU unplugged for quite a while before today, but I will go unplugg my battery for an hour or so now and see if that makes and difference.
Try this: Disconnect the negative terminal and then press the brake pedal for 30 sec. Reconnect the terminal and your ECU is reset.
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Old 17 Aug 2009, 01:08 PM   #5 (permalink)
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Re: Hesitation when accelerating

Tested the MAF, engine almost cut out when unplugged and indeled perfect again once put back in so guessing the MAF is ok

Ill try the ECU reset now and let you know If it helps over the next 24 hours.

Keep suggestions coming though just incase. Thanks!
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Old 17 Aug 2009, 01:27 PM   #6 (permalink)
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Re: Hesitation when accelerating

Quote:
Originally Posted by dougie175 View Post
Tested the MAF, engine almost cut out when unplugged
It almost cut out or it did cut out? If it didn't cut out completely then the MAF is probably faulty.
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Old 17 Aug 2009, 01:30 PM   #7 (permalink)
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Re: Hesitation when accelerating

Oh I dont know I plugged it back in about 2 seconds later and the revs came right back up, so it should completly stall when the MAF is removed?

The revs dropped loads when I removed the MAF I just presumed that was an indication it was working.
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Old 17 Aug 2009, 01:44 PM   #8 (permalink)
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Re: Hesitation when accelerating

You'll need to leave the MAF unplugged until the car cuts out. It should cut out pretty much straight away, if it does it may be fine. If it labours on for a while then you probably have a faulty MAF.
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Old 17 Aug 2009, 01:46 PM   #9 (permalink)
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Re: Hesitation when accelerating

Ok just did the MAF test again and no the revs drop for about 1.5 seconds and then straight back up to normal idle again.

Heres a video:
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Old 17 Aug 2009, 01:47 PM   #10 (permalink)
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Re: Hesitation when accelerating

ECU reset version 1001

Disconnect the negative batt lead... put key in and choose the ign position... depress foot pedal for about 30 seconds (this drains residual current) switch key back to off position
Reconnect the negative terminal
Switch key to ign on position BUT DO NOT START
Push accelerator pedal all the way down to floor and hold... then raise it to half position for a second then all the way off

Start the engine without touching the acclerator.. allow engine to idle for a few seconds and then drive for about 5 mins...

The ecu is now re-set

MAF test

Esure engine is at full operating temp
Disconnect the MAF lead
If the engine continues to run... even lumpy... the MAF IS FECKED
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Old 17 Aug 2009, 01:49 PM   #11 (permalink)
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Re: Hesitation when accelerating

I have posted a video of what happens when I unplug the MAF, just waiting for a mod to say its ok to view or something.

Video now approved above^^

Last edited by dougie175; 17 Aug 2009 at 01:58 PM.
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Old 17 Aug 2009, 02:03 PM   #12 (permalink)
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Re: Hesitation when accelerating

Quote:
Originally Posted by dougie175 View Post
I have posted a video of what happens when I unplug the MAF, just waiting for a mod to say its ok to view or something.

Video now approved above^^
That is one faulty MAF I am afraid.
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Old 17 Aug 2009, 02:06 PM   #13 (permalink)
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Re: Hesitation when accelerating

Thought so, Im in the trade (sprayer not mechanic dont worry lol) so can get parts at trade. However is there somewhere cheaper to buy mafs online than from Subaru trade as we dont get much discount from the Subaru dealer.

Thanks
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Old 17 Aug 2009, 07:38 PM   #14 (permalink)
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Re: Hesitation when accelerating

Pm me mate, can get you a new oe MAF at a reduced price from stealers.
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Old 17 Aug 2009, 10:01 PM   #15 (permalink)
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Re: Hesitation when accelerating

Damn, thanks for the offer mate, but just bought one from ebay for 96 delivered
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