Andymayo

Hi all ... new to Scoobynet ... hope you don't mind a Forester owner joining you. I'm literally tearing my hair out over a problem with my 2001 Forester turbo regarding what appears to be a hesitation problem. Engine is fine until I put my foot down and then it holds back making it dangerous to overtake. It will then fly when the turbo kicks in. No engine light on but took it to Subaru mechanic and his diagnostic said Lambda fault. I've now had this changed using a new £200 O/E sensor, changed cam belt recently, unplugged MAF meter which makes it worse, new titanium NGK plugs and also cleaned the Boost control solenoid. All this has made no difference :-( Anybody got any ideas at all on what to try next? Many thanks guys.

joz8968

iTrader: (13)

Of course you're welcome - its ScoobyNet after all; not ImprezaNet.

Coilpack/HT leads - microscopic hairline cracks leading to slight missfire, hence the hesitation??? Just a guess (could be a lot of things.)

PeeVee

iTrader: (1)

I note that you have fitted plugs, I assume they were PFR6 or 7's...Did you check the gap before you fitted them?

STi wanna Subaru

iTrader: (1)

new MAF.

Andymayo

Hi guys, thanks for the welcome and the replies. I left the plug fitting to my mechanic as it's a little awkward with no ramp but he has worked on Subarus before. It was him that suggested the titanium NGK's, all I know is that it has made no difference and he did say that the old plugs, although not a top brand, were the correct pale brown colour. He also checked the coilpack but did say it may be worth changing the HT leads. I guess that is the next thing on the list ... it's starting to mount up in costs now and not much nearer to solving. Only bought the car a month ago knowing that the cam belt needed doing and was told that was the cause of the hesitation. Obviously not :-(. I've also done a green/black plug reset and changed to 97 RON fuel. The car had one elderly lady owner from new and so I'm pretty sure has never been 'opened up' properly in all of it's 82K miles. Perhaps it just hasn't learnt how :-)

Andymayo

I was thinking of replacing the MAF anyway as it's reletavely cheap and easy but really wanted to be sure. Is there any way of checking it?

STi wanna Subaru

iTrader: (1)

It's similar symptoms to my 99 impreza had and a new MAF sorted it. commonish problem. On the impreza you could just buy the MAF if you had the part code. Not sure if that's the same for yours due to model and year. I paid about £80 for one. I'd try it before anything else if it was my car.

joz8968

iTrader: (13)

Although by no means a proper 'test' as such, the fact that the engine immediately ran worse when you unplugged the MAF, points in the direction that the MAF is doing something i.e. that the element must be measuring at least some air (but whether it's working within spec is another matter entirely.) [...Splitpin, I've qualified myself here, so lay off LOL ]

So, forget the above... The only definitive test is to get a mate to check its voltages in the car, while you go from idle to WOT. Idle should be around 1.0V... WOT should show around 4.5-5V (and proportionate voltage readings in between...)

Andymayo

Cheers for that guys, I think I'll give the MAF and HT leads a go and if that still doesn't cure it I may start to get a little more concerned :-(. I was also thinking of the rear oxygen sensor but then I thought this was purely an emissions sensor and so wouldn't cause a hesitation issue ... unless anyone knows any better! Thanks for all your help chaps.

PeeVee

iTrader: (1)

I personally would not waste my time or money changing the HT leads.

If your problem clears when on boost then it is unlikely to be HT lead related as they are under more load at this point & if faulty would cause a missfire here as well.

It seems from what you have said that it is likely that the plugs are correctly gapped, so I also would suspect a faulty MAF sensor, especially if it is the same type as the late classic impreza's (part no:22794AA010), these tend not to throw up fault codes as, even when faulty, they tend to operate within their tolerance but do not produce the correct feedback voltage for the amount of air being currently drawn into the system.

joz8968

iTrader: (13)

True.

But if, say, one lead is not badly fractured, etc. it can still cause a small missfire, which only manifests itself as stuttering hesitation, rather than an out and out "bang".

This can also rear its head when you up the boost, for example: they are fine std boost... but the extra boost is enough to find the HT lead/s weak point/s. This happened to me - 4 new coilpacks later, all is fine.

sparks_c/s

Always worth giving the MAF a good clean with some electrical contact cleaner( don't use anything else!), spray the see through thin plastic film on the inside and let it air dry, some times they just get dirty, may work, may not, but I've cured problems before with this.

Andymayo

Weird thing last night guys ... I removed the MAF in its housing to get the part number, ordered a new one, replaced the old one and hey presto ... almost perfect! Just a slight hesitation but 85% improved. Obviously on its way out and needs replacing anyway but obviously disturbed something! Cleaned the connector while it was off. Hey ho .... think I'm almost there, thanks for all the pointers guys :-)

joz8968

iTrader: (13)

Brill!

Do an ECU reset - it may just clear any badly learnt fuelling 'compensation' (because of the old MAF being out of spec.)

Andymayo

Will do Joz ... probably wait to put the new one in and then reset. New part should be here tomorrow. Many thanks for all your help :-)

STi wanna Subaru

iTrader: (1)

Glad you seem to have sorted it.... bet you wish you'd signed up earlier now

PS Knew it was the MAF

Andymayo

LOL ... sure do! I've only had the car for a month and although I had been reading the threads on here I didn't think to sign up as I thought it was an Imprezza site. I now know differently :-) ... much appreciate all your help and will be keeping a regular look on here as it's good to know as much s possible. I'd love an Imprezza but unfortunately a new baby and also a dog meant that the Forester turbo was the practical choice. One day ;-)

STi wanna Subaru

iTrader: (1)

Hopefully you can enjoy your car fully soon once the new MAF is in.

joz8968

iTrader: (13)

Obviously. lol

Andymayo

Well the saga goes on guys :-( ... put a new MAF in yesterday, ok it was off ebay for £70 and it was as if there wasn't one in there! ... Faulty cheap part then, my fault so will buy a decent one. Cleaned the old one that was running ok(ish) and re-fitted and all seemed back to normal so off I went to the football. Got 16 miles and the car lost pretty much all power, cut out when idling and I had to get it towed home. One thing I noticed was that it smelled hot and I could hear coolant boiling even though the temp gauge was normal. Last night I took off the wastegate and soaked in carb cleaner but still the same this morning. I can drive it now but it seems fairly sluggish and still smells hot and makes a sound of boiling coolant. Reserve was dry so topped up. Could all this be caused by the MAF or am I just getting a build up of faults? So annoying .... and I wasted a £25 match ticket. Had just put a tank of Ultimate in there too but it has run on this before.