I've got problems with my Impreza WRX (MY99):
when accelerating, the car jerks and shakes considerably. On the motorway, it has trouble keeping the speed, but when running slow (without the turbo engaged) there is no problem whatsoever. On idle, it runs just fine.
Anyone out there that has a clue to what this could be?
The guys at the repair shop didn't even know...but they told me that the turbo is just fine at least. Not much of a help: it still shakes and rattles...:-(

/G

 

Possibly MAF sensor failure. I had the same symptoms on my JDM MY99 - a change of MAF sorted the conditions.

Advice is to get the MAF checked ASAP as duff MAFs can lead to engine failure!!

 

As above. MY99s and MY00 are notorious for having weak MAFs

Do get it to a specialist asap, as a dodgy MAF leads to fueling issues which -in turn- lead to your engine letting go! Drive very gently off boost until it's sorted as a precaution!

Regards,

NS04

 

Thanks for the advice!
Maybe I should've searched and read the bbs BEFORE asking though? Seems as if a lot of you guys have had similar problems.
To sum up some of the proposed remedies:
- Check the MAF. Thanks MattPiece! This has been the problem for some of you. I don't remember who, but someone simply cleaned the MAF-wire from oil-smoke residue (or something like that), resetted the ECU and thereby solved the problem.
Okey, I'll check into the MAF asap. Don't want to ruin the engine...at least not this way :-)
- Boost solenoid: replace with a shiny brand new one, or at least clean the existing one, using brake cleaner. The BS gets clogged with oil or oil-wapors, apparantly, especially if you tend to overfill the engine (with motor oil, i.e.). I think that was Martins solution...
- Earth wires: beneath the intercooler (which has to be removed) is one. Behind the battery are two. Check that the wires are properly grounded. As Grant put it: "****ty electrical connections can be the cause of many non "limp home mode" where the ECU can still read the signal but theres too much resistance in the circuit to power the component".
- Fuel pump. Could be. But that should have shown up in the authorized repair shop...right? A SAAB-dealer told me that their fuel pumps brakes down after some 110000 km...but then again: that's SAAB :-)
- Spark plugs: decrease the gap distance to 0.8mm (not the recommended 1.1mm). Reset the ECU...problem solved? I just cannot understand WHY they recommended 1.1mm in the first place.
- Wastegate sensor. Faulty? Is this perhaps the "boost solenoid", or is there in fact a "wastegate sensor"?
- Knock sensor? Faulty, loose or surrounded by vibrating parts. If the latter is true, then the sensor may pick up vibrations that are misinterpreted as "engine knock"...which in turn leads to retardation and lower boost pressure.
Well. Didn't find any more, but I compiled this last night, and was kind of tired...:-)
More suggestions are welcome!

/G

 

A reset ECU on a duff MAF will cure the symptoms (but the car will be quicker! ) for a couple of days but they will return...

A new MAF is only ~£80, thus, IMHO, its worth just replacing rather than cleaning. I take the view that cleaning may cure the sensor whereas a new one will defo clear it! . FYI, with my symptoms, they came on gradually during few weeks. Major hesitation around 4-5K IIRC.

 

Yep, your right. I should really really replace the MAF...but I _could_ try to clean it first, and see if it helps. If so, then there I have it, right?
Your symptoms are exactly like mine; gradually worsening over typically a months time...

Perhaps this solves my problem. Extremely nice that Scoobynet exists, i.e. you guys! Thanks!! Because our swedish "experts" just didn't know _anything_, it seemed. Really amazing that they didn't have a clue. Their expert advice did however cost me £60...great investment...NOT.


/G

 

Try taking your handbrake off first....

 

Cleaning it could help, yet the problem may not be with dirt, etc, on the sensor. What I mean is, if you clean it and that doesn't solve the problem, you then dont know if its the MAF or something else totally unrelated. Of course, it may cure the problem, but there'll be this nagging doubt about when it will play up again....

One way to know if its MAF related is to put in a new/replacement/borrowed MY99 sensor. The other is the remove MAF sensor and check idle test - do a quick search on SN.

Do you know anyone with a MY99 (i.e. same MAF sensor)? If so you could do a quick swap and check it?

 

Hmmm..don't know anyone with a MY99, most of my friends drive SAABs or Volvos...or german cars...or even south-east asian cars...but maybe I could make a Hyundai MAF fit? Using grease and a crowbar?
If not, I really think that the repair shop (i.e. the AUTHORIZED repair shop), owes me...so I will make them help me. For free.
A question about resetting: somehow I thought that simply disconnecting the battery was enough, i.e. that disconnecting the car-battery made the ECU reset. But this isn't so, or am I wrong? I read all about the green and black connectors beneath the steering wheel (or wherever they are), so you don't have to repeat the procedure here, but is this true: disconnecting the battery DOESN'T reset the ECU?

/G

 

Problem solved.
A new MAF-sensor did the trick.
The acceleration is back, better than ever.
And I feel GREAT!!!
Thank's for all help!!


/G