Dr Who

Hi,
Can anyone shed any light on this, I have an MY97 Impreza that when driving steady i.e in traffic the car seems to be hesitant between 1200-2500 rpm but if driven hard there seems to be no problem at all, if anything feels to be pulling better due to having been serviced last week, problem was there before I serviced it (plugs/filters etc).
Any feedback would be very apprieciated
Thanks

s70rjw

iTrader: (2)

If it feels like a slight pulsing its quite common.Swapping to SUL in my MY00 Classic sorted mine.

Dr Who

Funny you should mention fuel, when the panic buyers drained the local fuel supplies a few weeks ago I couldn't get any SUL for a few days so I put half a tank of UL in to get by, I have since run the car virtually dry and tanked up on SUL and reset the ECU, it does feel better but there is still a hesitation present,
I was contemplating if an H/T lead was breaking down or something?

joedesi

Hello mate,

Funny u should mention that. About 6 weeks ago i noticed the same thing on my 97UK Scoob. I dont remember using different fuels...i always used optimax. Anyway the problem was intermittent and as i did motorway driving, most of the time it was fine.

Was coming back from work at 1am and was giving it a bit (approx 120mph) when i noticed there was a gradual lack in power. the car seemed to slow down and it became difficult to maintain motorway speed. Suddenly the engine died with a horrible metallic sound.

Took the inlet manifold off to reveal a bent valve. i didnt investigate further why it happened...it was cheaper for me to source a secondhand replacement. i would advise you to get it looked at ASAP.

Scott.T

iTrader: (2)

Different fuels cause different levels of hesitance.
Optimax IMHO being the worst, especially when the engine is cold
Esso SUL is slightly smoother when cold.

The lambda sensor can also cause this when the engine/lambda is cold.
If you disconnect the lambda you will probably find it alot smoother due to the ECU using the fuel base map rather then trying to achieve stoich AFR with a cold lambda sensor.

You can drive like this but re-connect the Lambda for MOT, or it will most likley fail.

Dr Who

Strange thing with mine is that if you caine it, no problem, it goes like stink! It only seems to do it when you drive steady, i.e in built up traffic just seems to of developed in the past two weeks.

Scott.T

iTrader: (2)

Do an ECU check, you may find that the 02/Lamda sensor has died, fault code 32.
The 02/Lambda is not used when you 'caine-it', hence why it will drive O.K

ECU Reset/Diagnostics

Turn ignition OFF

Connect Read Memory Connectors & Test Mode Connectors : 2 black connectors under dash, connect black to black & 2 green connectors under dash, connect green to green

Turn ignition ON (engine off)

Engine Check lamp turns on

Depress accelerator pedal completely

Then return it to the half-throttle position and hold it there for two seconds

Release pedal completely

Start engine

Code is indicated by Pulsing lamp

If a fault is detected - Check ECU Code

If no fault is detected - drive the car sensible for a couple of minutes
i.e. until warm (do not run tall & do not thrash it!)

When the ECU has been reset the Check Engine Light will flash

Code is indicated by Pulsing lamp

If a fault is detected Check ECU Code

Turn ignition OFF & Disconnect Connectors

If there is a fault Check Appropriate Sensor

Fault Codes

A fault code is defined as a slow flash followed by fast flash i.e 2 slow and 3 fast = 23 Mass Airflow sensor.
A continuous on/off at the same speed is no fault found.

Code ITEM
11 Crankshaft position sensor

12 Starter switch

13 Camshaft position sensor

21 Engine coolant temperature sensor

22 Knock sensor

23 Mass air flow sensor

24 Idle air control solenoid

31 Throttle position sensor

32 Oxygen sensor

33 Vehicle speed sensor 2

35 Purge control solenoid valve

42 Idle switch

44 Wastegate control solenoid valve

45 Pressure sensor –Pressure exchange solenoid valve

51 Neutral position switch

Dr Who

Have reset ECU and checked fault codes, nothing showing. Drove home tonight and still flat, Can the Lambada fail and not show a fault code? Only reason I ask is a friend of mine took his MY99 to a dealer a while back and had them check it out, they said the lambada was u/s as it was constantly reading zero, apparantly it should read either a pos/neg parameter, can anyone verify this?

Scott.T

iTrader: (2)

You can drive with the lambda disconnected and it won't log a code. Try that first.
But it should log an error when doing forced diagnostics

Dr Who

Have driven the car in ecu reset mode as described above and the problem goes away, disconnect the green/black connectors and car starts hesitating again?
Seems to me a sensor playing up! Spoke to a dealer this morning who informed me that lambada sensors and A/F meters can go out of calibration only way to check it properley is get the test equipment on the car

Dr Who

Drove it last night with lambada disconnected and car didn't like it at all, running very rough and didn't want to accelerate.

Scott.T

iTrader: (2)

It should run fine with it disconected, many on here will testify that (including Bob Rawle). I suspect the problem lies elsewhere then, maybe MAF. As the MAF will be providing the prime signals for controlling the fuelling when the Lambda is disconnected.

When my MAF failed it was v.v.hesitant pulling away.

I would get it checked ASAP because although it's running well under load it may be running lean due to a possible faulty MAF.

Dr Who

It looks like it may well be the MAF sensor, phoned dealer, a new one is £275 problem is I am currently checking out several after market ECU upgrades some of which do away with the MAF and use a MAP sensor instead so the ECU may get upgraded sooner rather than later.

gazman

that seems expensive


Just paid £80.00 for mine (MY99)

Dr Who

Yes An MY99 one is cheaper as it is a different unit, I confirmed this last week with a dealer, only alternative is a second hand one but I didn't really want to go down this route.

Dr Who

After a few weeks of messing about and experimenting I have finally cured my hesitation, Yes it was the MAF sensor replaced it and we are now back to normal so no more spluttering down the road in a morning!
I am now off to purchase a Apexi Power FC
Cheers,
The Doctor

Chad!

Hi guys. I have a problem with my Scooby that sounds very very much like this problem of hesitation at low end driving. BUT, I'm very new to subaru's so don't really know where to start. Mine currently runs on Optimax. Don't really want to mess with the reset mode by using connectors as I don't want to hurt anything. The problem with the MAF sounds like it may fix it BUT, I aint sure where or what this is. Can someone describe it for me and where it is? Or even better, post a piccy?? Can this MAF not be fixed if it is faulty? Does it have to be replaced?? And is there any way of knowing/testing it to make sure it's faulty before I buy a new one? My car is a 99.

Many thanks,

Chad.

ver

the MAF is a sensor that really can't be repaired or at least easier to replace.
there is a pic somewhere as I had a similar issue and someone was kinf enough to show me a photo (could be another forum but I will dig it out) The sensor can be tested and really needs you to know where it is.

basically start the engine and allow to run until warm and disconnect the sensor. If it stalls then the sensor is working correctly as it is taking air mass readings from it. If it continues to run then obviously it is disregarding the sensor i.e. not functioning and using its own ecu fueling/air maps to compensate.

hope this helps

I'll look for the pic

ver

Check this thread

http://http://bbs.scoobynet.co.uk/sh...d.php?t=454420

working on it

link not working

ver

does this work now?

http://http://bbs.scoobynet.co.uk/sh...ing+MAF+sensor

if not search for changing MAF sensor help

theres a thread I asked and theres a pic and a description there

Chad!

Hi, thanks for that. I had a feeling that was the MAF but wasn't 100%. I read your thread too. The thing now is, mine idles perfect. It's only when your driving at around the 1500 - 2500rpm range. As soon as it comes on boost it's fine. Could this still be my problem do you think?

ver

Personally I think it could be the MAF. maybe worth a check on your maf sensor to see if it stalls pretty quickly or overruns then stalls (indication its on it way out)

is it worth spending the money and buying a sensor to try? then at least you'll have one for when it needs changing..... or borrow from an owner perhaps?

Sorry I can't be more help pretty new to the scooby game myself.....

Chad!

I'll try that in a minute (disconnecting it). If it keeps running I suppose I'll be happy. At least I will of found a problem. And you have been helpful cause I hadn't got a clue where to start with this kinda problem. I'm very new to this kinda car/engine etc. Never really worked on anything with a turbo before so everything I touch I'm worried about breaking something. Suppose I'll get used to it sooner or later.

Dr Who

When I had hesitation thats all I had, the car idled perfect, didn't cut out or anything, once on boost it was perfect, replacing the MAF meter cured the problem also seems more resoponsive top end,
The one thing I was told to do was disconnect the Co2 sensor and see if the car would run just on the MAF sensor, it wouldn't so I replaced MAF sensor and problem solved, My advise would be try and find someone with same MAF sensor and swap it over

Chad!

Hi, thanks for that. I did try disconnecting the MAF whilst it was running. When the engine was cold and I unplugged it, the revs dropped for a moment then went back up. I tried the same thing when the engine was fully up to temp and the engine died. I would of thought this is how it is supposed to act? So the next thing to try would be the C02 sensor then?? Hmm...where's that then?? Aint got a clue on these so you'll have to bare with me....sorry. Still learning.

Thanks,

Chad.

Chad!

Hey guys. Finally fixed my problem.......I think. It's been ok since last night anyway. All I've done is gone from Optimax fuel to regular Unleaded. Thought it was worth a try and it seems to of paid off. It's only very very slightly noticable now, and I do mean slightly. I reckon when the Optimax has all been used (diluted but some still in there) it will be fine.