Rajaman

iTrader: (3)

Hi All
I've had the car for a couple of months, I bought it off a fellow SN member, It's got a hybrid FMIC, VF28, bailey DV, K & N Induction kit, Samco Hoses, uprated leads, Ecutek remap and is running 320 - 330 bhp mapped for 1.3 bar boost, the car was worked on by API and is badged as an API 330 with 126,000 miles
When I bought it , I had the timing belt done, and all fluids replaced with back pads from my local performance spacialist, replaced the entire mild steel 3" exhaust system with a SS 3" one, car then ran fine for 1.5 months before it developed this problem
When accelerating with WOT in 2nd gear, the car starts to make boost nicely and revs freely untill it gets to approx 4k rpm, where it seems to hit a massive flat spot, it's not violent like a fuel cut, but it wont rev any further using WOT, exactly the same symptoms in the higher gears when accerating WOT, only slightly earlier in the rev range ( I'm presuming in relation to engine load ).
When accererating in 2nd using partial throttle, the car revs cleanly through the rev range, making boost
The car idles perfectly, doent use any excessive oil, no smoke and displays no diagnostic fault codes, and apart from this problem runs perfectly in every way.
I have worked my way through the following
I bought a brand new MAF from the dealer, fitted it , reset the battery, no improvement.
I bought new 7B plugs, had them gapped correctly, no improvement
My pal on here has a v6 sti, so we swapped over the follwing parts from his car to mine to try and eliminate the problem
Coil pack, no improvement
Boost controll solenoid and map sensor, no improvement
When the boost controll solenoid pipework is disconected, and I connect the turbo outlet straight to the actuator, the car pulls cleanly using WOT, although obviously is producing only limited boost.
I have tried connecting a MBC, and when it is set to approx 1 bar, the car displays the same hesitating symptoms on WOT
I've since changed the fuel pump and fuel filter for new ones, and have used forte injector cleaner, no improvement
I'm almost at my wits end
I've checked it over along with a couple of mates and my mechanic for air leaks, split hoses etc and all seems fine, but have not had the car in the air to inspect underneath
The only other thing I could think of that it could be
TPS ?
Lambda sensor ?, although wouldnt this throw a fault code if faulty and I'm not sure if it correlates to the symptoms my car has
Speed sensor ?, although the speedo on my car works fine
Immobiliser ? Although the standard OEM alarm / immobiliser seems to be working fine
FPR ? Could the performance of the OEM FPR detoriate over time, so that it cant supply enough fuel when the engine is a max load

I really dont know what to try next, If I dont get anywhere with it soon I'm going to bite the bullet and take it to a specialist, I've only heard good things about Zen so it will prrobably end up going to them, it's just I would love to get to the bottom of this myself. This is my 5th Impreza, and I never had any bother with any of the previous ones, and I like to think I know my way around them
I've been through 3 tanks of v power since the problem started, and numerous battery resets so bad fuel can be eliminated

Any ideas or help will be greatly appreciated, I've searched on here for days, and read all threads that I thought were possibly related, but still havent got any where
R

Rajaman

iTrader: (3)

OH, we also removed the DV, and blanked off the pipework, no improvement

Splitpin

Reading your post the throttle position sensor is an obvious thing to look at.

The one thing we can say it won't be is the lambda sensor, as your car is in open loop fuel control when on boost so the O2 sensor isn't affecting anything. But, to answer your general point on these, a lot of the time they don't throw a CEL even when seriously degraded. Same with airflow sensors - although that shouldn't apply in this particular case.

As a matter of interest, do you have a boost gauge in the car, and if so do you see the boost dropping when the car goes flat, or does it stay pretty much the same?

Also, what happens when you accelerate on slightly less than full throttle - say half and 3/4? Still goes boring, or...?

Worth swapping the TPS over with your mate's 6 but make sure you use a marker pen, scriber or whatever to note carefully the orientation of the TPS against the screws, and put it back in exactly the same place, otherwise it might make his run a bit weird.

If that doesn't throw any light, best way forward is probably a specialist. You need this diagnosed via a Select Monitor or better. Chances are the cause of the problem will be apparent pretty quickly once someone can see what the ECU is actually doing (and the inputs it is responding to) at the point it drops off the boil.

Jolly Green Monster

iTrader: (4)

TPS is only used when you change the throttle position.. ie you go from part to full throttle.. fuel is added to compensate for the sudden change is air the engine consumes.. unless the track in the sensor is broken and it therefore varies the voltage but not normally WOT but cruise as the track is worn out with use.

Is it on the standard inlet pipe ? if so check it is not split where it mounts to the turbo.

If not standard and a samco or similar it might be sucking shut.. try adding jubilee clips around the outside of any areas it is squishy.. usually next the power steering pump etc.. it then cannot go oval and suck shut

Simon

scoobynutta555

Take a look at this thread
https://www.scoobynet.com/general-te...-uk-model.html

Mine is post number 17 and mentions the same problem you had. My car had the API 320rebuild and map. Everytime you floored the gas at around 4k the car would hesitate/judder/det or whatever the phrase is. I was told as the car was several years old the electrics were old etc, basically bull5hitted off. The only cure was to put a DAWES on and lower the boost. I was just too pi55ed off with it all in the end to find the root of the problem and API obviously didn't habve a clue. I suspect it's a widespread problem too as I've seen this mentioned before.

Also, don't bother going to Zen as they originally mapped the car. I brought it back to them to finally sort the problem and basically they couldn't. They did say try a 3 port solenoid, but again, this would be added expense with no guarantees.

APIDavid

iTrader: (4)

Try using a bleed valve and hand set it to target boost - let's say 1.35 bar . What it does is act as a safety valve and bleeds off all boost registered above 1.35 bar. A simple and effective cure [ and cheap ] for overboost, and the resultant jerk on fuel cut.

Sometimes it can be very time consuming to go looking for an obscure reason why a car overboosts and given that each hour that is worked on a car attracts a labour cost, it is often a way out for the customer that doesn't cost heaps.

However, using a bleed valve as your sole means of boost control is a VERY BAD IDEA and I do not advise that at all.

David APi

Pavlo

Actually I have had your car back a few times now with it's new owner, and as I suspected when I struggled for the best part of 3 hours to get your boost control working properly, there was a hardware fault causing sudden erratic boost control. The changes made by the new owner have meant no problems sorting the boost control, they fitted a 3 port solenoid (and a FMIC) and we got rid of the dawes device.

At the time you suspected a mapping issue I obviously I offered to fix your mapping FOC. However, once I found it was not a mapping issue and instead a suspected hardware fault, I charged you £100+vat for half a day of my time (a heavily discounted rate I might add). Given that I was not responsible for any mechanical work carried out on your car, I believe I have always been fair and tried to help wherever possible. Unfortunately, there can never be any gaurantees that a suggested fix will work 100% as there are so many parameters to factor in. In this case my diagnosis was spot on and the solution was fairly cheap and did work 100%...

Ironically enough your old car is here today, last time it made over 350hp with the few extra mods.

Paul

Pavlo

Sounds like it's running very lean once you try and make decent boost, which could be down to a faulty or badly fitted FPR, a failing fuel pump (have you checked to see it's a proper walbro?) alternatively it's a leaking intercooler hose which will have the opposite effect and make it choke with too much fuel (and some black smoke).

With datalogging and some experience I don't see it being a difficult fault to find.

scoobynutta555

I'm quite glad the issue has now been sorted. My thanks to your heavily discounted day rate. Also bear in mind I was expecting a properly functioning car running at 320 bhp which cost me several thousand quid and a great deal of wasted time.

I must say the whole episode has disillusioned me to the extent I sold the car at a heavily discounted price of around £4k and to make me question myself even buying another impreza, even a standard one. Well done to the new owner and his properly functioning car. I might still own it if it was done properly the first time round.

Pavlo

Thanks Vaughn.

Rajaman

iTrader: (3)

UP
This is still happening and I've hardly driven the car as a result and now finally want to get it sorted

Splitpin

As said above, more than once, you need to get this looked at by someone who can monitor/log it.

It should be relatively easy to work out what's going on once one can see what sensor inputs the ECU is seeing, and how it is controlling the engine as a result.

[-(o)-]

iTrader: (1)

This happened following a new exhaust? Sure its not something in the exhaust? Failed cat causing a blockage or similar...

Otherwise as above get it to one of the specialists on here, API would make sense or if you're closer Zen etc. Theres times when its better to admit defeat, I've been there.