Hi Guys,

Right ive searched around but struggling to find any good answers to my problem.

My car is an MY00 UK Turbo classic. The car itself runs and drives lovely, boosts fine, no issues while driving, but when i come to a halt (traffic, lights, junction etc) the idle drops low then picks back up, repeats a couple of times before it settles, as if it wants to cut out. Once its settled its fine, and starting the car up it idels fine, and as said generally drives fine. Its pretty annoying though and id like to fix it.

I never get the check engine light on while driving but very occasionally it will come on when i start the car from cold and stay on for about 10 seconds or maybe flash a bit, before going off quickly and staying off, normally it doesnt do this, and as said it never comes on while driving.

I took off the ICV and gave it a clean up, but hasnt really helped, so tried reading the codes and it threw up 22 (knock sensor) and 32 (a/f sensor or o2 sensor).

The car does have a forge dump valve which im led to believe can affect the idle?
It also has a decatted haywood & scott exhaust system, which i know from previous cars ive had can affect the CEL light but not be a problem as such. Is this case?

I basically want to know if its going to cause a problem if i leave it, and these faults are just showing due to mods, or if i generally have an issue thats going to cost me in the long run?

Ive read on here on one post that all i am likely to get is an annoying idle and high emissions but no serious problems but ive also read some scary stuff....

In case anyones interested i get about 19-20 mpg but do short journeys everyday with a lot of stop start so i dont think that is drastically bad.

It also has an uprated intercooler (v7 STI top mount), k&n panel filter and an apexi AVC-r boost controller and has all been remapped by powerstation.
Any help or advice would be appreciated.

 

Most likely and on that year of car I would advise buying a new maf sensor

 

Yeah, The same issue on mine, and it's defo caused by the leaking bov.

Let someone block the bov with a hand, and blip the gas pedal, if it doesn't stall, then you know what it is

By the way on my car it was discovered by Simon (JGM)..
do you remember Si?

 

The fault codes didn't throw up the maf sensor, why do you reccomend changing it ifs apparently okay ?

An when you say block of the DV you mean cover up the holes while the throttle is blipped? Presuming the car should die when covered up and if it leaks then it won't?
That still won't solve my issue of the two codes I have though?

 

Because been there many times before and its still within range so ecu doesnt know whats at fault.

Dv is also s good call

 

Ah I see. So if its the dv then it's not going to cause long term issues but just be an annoyance?
And regarding the codes the car throws up could that just be the ecu getting confused due to the DV / decat? Or am I way off...

 

If its decatted it should be mapped and the issue investigsted and resolved at the same time

The description of the idle issue sounds like dv leak or maf sensor.

The error codes could be something else or related.

 

I have got the same issue,I have changed the inlet manifold for a nice polished one that i got cheap. idled fine before? so dont think its the maf and i have since put my own icv on so dont think its that, but i have read about doing an idle re-learn after disconnecting the battery, will let you know how i get on

 

If the age of the mag is unknown then I would change it regardless! A failing mag can end am engine!

 

 

The few things I've read recently about maf sensors destroying engines completely contradict what I once thought about Subaru boxer engines being really reliable... It's quite a shock to be told a slightly lumpy idle on a car that drives perfectly can destroy your engine !!

Maf sensors seem quite expensive too ! What the O2 sensor and the knock sensor? Should they be replaced as my car is showing them as the fault codes.

Jollygreenmonster, the car was mapped for the mods it has but was with a previous owner at the time, and I'm sure it didn't have the idle problem when I bought the car, it's just started recently.

 

The engine is reliable, but like any other engine, if you run it lean because of a maf sensor issue then you can melt a reliable engine!
I consider maf replacement on MY99/00 as part of the general maintenance and if you regard them as expensive then heart failure is on the horizon if it takes your engine out!

 

Haha, so it's worth replacing the maf sensor just to basically rule it out, then if problems persist take it from there. Should I worried about the knock sensor/O2 sensor issue?

 

I say deffo replace it! The ecu will not pick up a "failing" sensor and that's where the danger lies. I used to replace mine every 2 years!
Unsure about the other two sensors!

 

Just looked on eBay and looks as if I can get for about £40 new but not a genuine Subaru part. Have you tried these? I presume they will be fine ? Or is it worth going genuine ? (Significant price difference).
I also presume they are easy to chance? Just unbolt the maf from the housing while its all still connected up and plug it back in, jobs a good'un?

 

Don't get a non-gen MAF on!

I tried that - the car ran worse with it on, over fuelled it like hell...

I put a new genuine MAF on & was fine

As the guys above say, the MAF's on these year cars are a common thing.

 

hi guys where is the best place to get a genuine maf sensor for my scoob its a 99 impreza 2000 turbo uk spec, part number is 22680AA301, thanks for any replies.

 

best price i have found it £124 on worldcarparts.co.uk is that a good price

 

Think they are 100 from main dealer

 

ok the one i found was 310 at the end not 301 i hope its not just me but i cant find a replacement maf anywhere, getting slightly peed off now as i have found one for every impreza but mine???

 

Easily got from a main dealers when you supply a chassis number

 

I replaced the maf (which hasn't fixed my problem btw so waiting on an O2 sensor now) and I ordered it from the main dealer, was £120. Give them your reg or chassis number they will supply you the correct part.

 

In case it helps people searching for this problem in future, i now think ive sorted it.
Repalced the MAF with genuine part - did not fix the issue but did clear the knock sensor code, cost £120 from the dealer.
Bought a second hand oxygen sensor from andy @ scoobyspares for £30 (as dealer was £180), fitted it and the issue seems to be resolved, code has cleared, idle is okay, drives fine. Will see if MPG is increased.
Should of tried that first as that was the code! but at least im now running with a nice new MAF too.