Just bought my car, and have a problem!!

[Quackers]

Hi All,
I have just picked up a T plate scooby (private sale), but it has massive missfire through the rev range underload, I drove it 170miles not fast and didn't notice anything wrong but the last 20 miles or so I floored it, only to find its running like a bag of poo! Lots of jerking acceleration, bursts of speed mixed with large flat spots.
Any Ideas would be very helpfull I will look tomorrow.
Cheers
Tim

[stockcar]

on that age would be looking at the MAF sensor first............

[Quackers]

I just drove it round my mates who used to have a T reg one and he said the same, said he paid about £50 for his MAF, also he mentioned the O2 sensor, I rang the man who sold it to me and he seemed genuinely suprised, and asked me to keep him posted tomorrow, I dont honestly think it was faulty before, i think on the way back it has developed a problem!
I dont supose there is anyone in the Norwich area that can drive it to see what they think?
Cheers
Tim

[Quackers]

Just drove it again and if you just use squeze throtle carefully it dosn't hesitate so much as flooring it, plus turned the turbo down and its not as bad but slow and it was working fine with abit more boost.
Cheers
Tim

[Anders52]

Prob is m8, there is a myriad of things that could cause a miss-fire.

Anyway the o2 sensor only works in whats called closed loop control.

When you are cruising and the engine is under no load the o2 sensor has an influence on how the engine uses fuel to achieve the best mix to assure the car produces the least amount of pollutants. Closed loop.

Under load ie when accelerating the car ecu goes to open loop mode which disables the o2 sensor.

In essence under load there are 2 "control loops" fighting to control the engine. The primary control loop says - throttle is open further than it was so chuck more fuel in. While the O2 sensor say whoa there too much crap in the exhaust gases so trim the fuelling level which counteracts the primary loop.

To make the engine produce power the "economy" (O2) sensor needs to be disabled so the power "primary" loop can run. This is why cars are tested at mot time at idle or at a constant 2k revs (from memory).

This is a generalisation of how the ecu works and there are loads more factors involved but as far as i know every ecu manufacturer adopts the same principles.

From what you say, its either something simple like a fouled spark plug / lead or the coil pack that is failing when under load.

Can you describe the prob a little more and have you checked the ecu for any fault codes?

What mods does the car have also?

[Anders52]

Sorry m8 just found your last post.

What do you mean by turning the turbo down? have you got a independent boost controller?

[uk dave]

Originally Posted by Anders52

The thing that annoys me is that everyone blames the maf when it may not be the problem. There is a myriad of things that could cause the same thing.

Anyway the o2 sensor only works in whats called closed loop control.

When you are cruising and the engine is under no load the o2 sensor has an influence on how the engine uses fuel to achieve the best mix to assure the car produces the least amount of pollutants.

Under load ie when accelerating the car ecu goes to open loop mode which disables the o2 sensor otherwise it cant produce power. This is why cars are tested at mot time at idle or at a constant 2k revs (from memory)

From what you say, its either something simple like a fouled spark plug / lead or the coil pack that is failing when under load.

Can you describe the prob a little more and have you checked the ecu for any fault codes?

Nobodys on about the o2 sensor though soz chap im either with alyn on the maf dont forget 99/00 uk`s(if it is) are prone to maf failure-i know ive had one go, coilpacks are only relevant if a wrx classic,uk`s are a normal set up,or im with you on plugs/leads. If i`d bought private though i`d give it a full service meself first anyway.

just hope its nothing major quackers,had a missfire on mine at the top end of the rev range and just turned out to be plug gap-set mine at 0.8mm and its sound, generally ppl say around 0.7-0.8mm go with 0.8mm i tried both an this were better.Other thing it may be is ya boost solenoid acting up have had trouble with this too though once cleaned out is usually ok-however note if your cars fitted with a boost controller the std boost solenoid will have been replaced with one supplied with the controller an this wont be relevant.

[Anders52]

Originally Posted by uk dave

Nobodys on about the o2 sensor though soz chap im either with alyn on the maf dont forget 99/00 uk`s(if it is) are prone to maf failure-i know ive had one go, coilpacks are only relevant if a wrx classic,uk`s are a normal set up,or im with you on plugs/leads. If i`d bought private though i`d give it a full service meself first anyway.

just hope its nothing major quackers,had a missfire on mine at the top end of the rev range and just turned out to be plug gap-set mine at 0.8mm and its sound, generally ppl say around 0.7-0.8mm go with 0.8mm i tried both an this were better.Other thing it may be is ya boost solenoid acting up have had trouble with this too though once cleaned out is usually ok-however note if your cars fitted with a boost controller the std boost solenoid will have been replaced with one supplied with the controller an this wont be relevant.

I know m8, just i read his post where his friend mentioned the o2 sensor and hence i posted - I did edit my post as it was a bit off

Thing that got me was the fact it was a massive mis-fire, if the maf was that far out then it would bring up the cel.

If its the maf then subaru have made a major f*** up with there fault monitor in the ecu is all im saying.

Also im not sure what you mean by coil packs are only relevent by wrx classics? Whats the difference between my my97 uk turbo and a 00 or a 07? Do they use individual cylinder trannys instead of the wasted spark trannys i have aka coil pack?
Doesnt really matter as a coil can fail at anytime and is usually only noticeable under load due to the higher frequency pulses.

Im also not sure what he means by turning the boost down... how does he achieve this unless there is another controller involved or adjustable wastegate? and this in itself could cause probs...

Start with simple things first before we head down the expensive route like maf's

Need more info, for example is it a mis-fire in one cylinder?

[rikimaru]

Originally Posted by Anders52

Thing that got me was the fact it was a massive mis-fire, if the maf was that far out then it would bring up the cel.

If its the maf then subaru have made a major f*** up with there fault monitor in the ecu is all im saying.

Not neccasarily. Mine didn't show up on the CEL. I arrived at the conclusion by deduction and then did a diagnostic. I'm with stockcar on this. I'd go with the MAF sensor. Mine was like that and then progressed to cutting out at idle and revving all over the place.

[Quackers]

Hi All Thanks alot for all your responses.

Right, this car is standard apart from a Blitz dump valve, RamAir filter and a Bleed Valve (I know its crude) but when its turned off it feels like there is hardly any turbo at all, no sit in the seat feel at 3000 revs or so just a very even and light turbo feel which gets better as the revs rise (still its hard to tell if the turbo is doing much, there is a nice rush of air sound from the filter as the turbo spools up), the stuttering is still there but noway as bad, its almost ok.

As I change gear, flat out, there is a big Jerk still.

If I intrduce a half turn to the bleed valve (where it was when i bought it) it runs like a kangaroo up the rev range, almost like its off/on/off/on boost. It seems like fueling.

It does feel like it would be much quicker if it was not messing around, and feels more like I remember my friends Std one (not rocket fast but you can actually feel a turbo boost).

Another bad thing is that when turning sharp left there is alot of knocking feel through the steering and almost feels like the offside front tyre is flat! Is this drive shaft? Cant feel any play in the wheel bearing whilst on ground.

Can't wait to get this car sorted.

Cheers
Tim

[Quackers]

PS.
There is no engine management light on which I find hard to understand given how rubbish the engine is running.

[uk dave]

Like rikimaru has already mentioned a faulty maf doesnt always bring a faultcode on classics, mine didnt untill i tried cleaning it took off cleaned put bk on faultcode -only took off to clean as it were running so crap though to be fair were glad it threw a code coz its still about 70-80 quid-ish for a maf sensor if i remember right-lot of money if its fine.

[uk dave]

Originally Posted by Anders52

I know m8, just i read his post where his friend mentioned the o2 sensor and hence i posted - I did edit my post as it was a bit off

Thing that got me was the fact it was a massive mis-fire, if the maf was that far out then it would bring up the cel.

If its the maf then subaru have made a major f*** up with there fault monitor in the ecu is all im saying.

Also im not sure what you mean by coil packs are only relevent by wrx classics? Whats the difference between my my97 uk turbo and a 00 or a 07? Do they use individual cylinder trannys instead of the wasted spark trannys i have aka coil pack?
Doesnt really matter as a coil can fail at anytime and is usually only noticeable under load due to the higher frequency pulses.

Im also not sure what he means by turning the boost down... how does he achieve this unless there is another controller involved or adjustable wastegate? and this in itself could cause probs...

Start with simple things first before we head down the expensive route like maf's

Need more info, for example is it a mis-fire in one cylinder?

Wrx`s have individual coilpacks per plug which fit above the plug and are very tempremental when disturbed.

Wrx no single coil



my uk turbo with coil cant be planer than that.

[michael1275]

This sounds very much like fuel cut to me, have you got a boost guage. you must have if your running a bleed valve or your mad. set the boost to 1bar no more or better still remove the valve and put back to standard or you could blow it up

[tom73]

got to admit, when i first read the thread, it sounded like fuel cut. symptoms sound exactly the same as when mine blew the pipe off the boost solenoid