Marky-San

When giving some welly onto motorway, and 4,000 rpm the car was beginning to shift - when BAM!! sudden brick wall feeling as if the rev limiter had cut in.

Any ideas what this could be?

nom

Fuel cut springs to mind.
If it is, not to worry unless it starts doing it a lot

Marky-San

Can it be rectified? Its not exactly the greatest feeling being catapulted forward.

Gussie Cup

Sounds like it could be overboosting - a total pain in the ****!

Do you have a boost guage fitted? Can you see if the boost suddenly flies up towards the end of the dial just before it happens?

Ben

KOZIKOT

I've got the same problem,try reving it at tick-over, does it do the same ?If so I've being informed it's the speed sensor........

nom

The most likely thing from what you described (booting it at 4k) is going to be fuel cut. Fuel is always cut for safety, but is a temporary work around for occassional problems - it's not necessarily an indication of anything going wrong, just - for example - it was a cold day so you got overboost.
However, if it does it repeatedly, it needs to be looked into. Boost missing its target is the problem - but this can be caused by a number of things, mainly the fact that you're probably running a 2-port solenoid which is technically described as 'pants' . But it does the job most of the time.
It can be stopped by a lot of things, depending on what the problem is! Permanently reducing the boost gets it done, but is sort of missing the point... again, just wait to see if it does it again!

Marky-San

Yeah, doing it quite a bit - never did it before at all.

Hmm...I'mm try the MAF idea and see if that helps.

BoxerFlat4

nom - I believe Marky-san has an early STI, which I understood had the 3 port solenoid.

Waiting to be corrected, though....

Marky-San

Is that good or bad - I cant tell LOL!!

BoxerFlat4

Marky-san -

The 3 port solenoid is preferred to the later 2 port, it basically controls boost better. It should limit the chances of it being overboost, to me it sounds like you've hit the fuel-cut limiter.

Do a search on fuel-cut, several things can cause it.

Marky-San

I've read that fuel cut seems to happen more on a corner - this does it on the straight. Read also that cold can affect it - the weather today is quite mild.

I also have 3/4 tank of petrol in car, not a 1/4 as most people report.

I dunno?

BoxerFlat4

Marky-san -

Your confusing fuel "surge" with fuel "cut" - fuel surge is when the tank runs low, as you correctly said, and the pump can run dry due to the fuel moving around too myuch inside the tank.

Fuel cut is a defense by the ECU, triggered by various things, as an attempt by the ECU to protect the engine.

Marky-San

Ah, confusion mist clearing - so I need to find the possible problems associated as you say then?

Cheers Paul - I'll add that to the list of things to check.

The list is getting longer every hour or so (hehe!).

Gussie Cup

First step would be to clean the Wastegate solenoid with some carb cleaner.

On the drivers side inside wing (just behind the airbox/Induction kit) is the solenoid - clean it out and see if that cures the overboost.

Ben

hail-hail

I had this in both my STi RA and my STi3 both cured with the Wastegate Carb cleaner spray.
Once the boost cut, i.e. the brick wall feeling it would go again and then cut again, if I accelerated more smoothly it was fine.

Where in Strathclyde are you, I comne from Ardrossan

Gussie Cup

Hail Hail - Had it in both of mine as well. You can 'drive around' it by easing off the pedal around 4000 rpm but then sometimes it would cut in earlier and sometimes later - was so irritating.....

Still, had a Unichip fitted and it now holds 1.4 bar boost from 4000 rpm. Puts a nice smile on ya face!

Ben

Marky-San

Gussie Cup - its exactly as you say - drive smooth no probs. Nail it and smack head off windscreen.

Hail hail, I live in Motherwell mate. Till next year anyway originally a weegie though.

I've contacted the previous owner of my car and he says it happened to him, now got to unplug some connectors under the steering wheel which will start a self clean cycle for the boost soleniod. He said this usually cleared it - Ill try tomorrow and post back the result - hopefully positive for a change-hehe!

Paul_M

SOunds like hes just getting you to reset the ECU, the solenoid wont clean itself you need to spray in some cleaner.

It definitely helps to have a boost gauge with things like this though so you can see what boost is doing cos it definitely sounds like fuel cut due to overboost. Shouldnt really happen unless the boost has been increased and fuel cut not raised.

Marky-San

Have boost gauge but it doesnt spike when it happens. He said that its happened before, and he did have to use spray to clear it (me error). Hopefully that clears it

TonyBurns

iTrader: (3)

Definately overboosting, what mods (if any) do you have on your car?
The other thing it could be is a clogged wastegate (but highly unlikely as you would also loose performance) and if your not loosing boost there......

Tony

911

Just cured for good the same 'brick wall' problem.
My STi V3 had exactly this problem. cleaned the 2 port sol, no difference, violent fuel cut still. Took it to Power Eng in London, found it to give 1.6 bar at 4000! No wonder it went well...
Mervyn fitted a Blitz boost controller, set it to 1.2 and gave me 314 bhp! No brick walls at full chat anymore! Cost a bloody fortune, but a blown piston or 3 costs more.Note that if you have a turbo back exhaust the problem is WORSE.
Graham

Fantom

try the spark plugs???
should be gappen at 0.7mm rather than 1.1mm

Marky-San

Only performance mods are HKS super flow induction kit, some jap s/steel exhaust of unknown origin.

Why would the problem only show up now though?

Paul_M

Dunno somethings obviously causing the boost to go higher than it has been previously. What's it hitting on the gauge before the cut and is it any higher than it used to peak?

911

When I had the car 2 years ago direct from Japan, bog standard, it drove realy well, no fuel cut at all, then one early, cold morning blast it appeared out of the blue. This was a tank of petrol after filling with Optimax! Had been using simple Super Unleaded to that point. Changed back to super but the problem was still there and stayed untill the Blitz.When I cleaned the solenoid and pipes with brake cleaner nothing came out except the cleaner clean as a whistle.
The Blitz cost 900£ fitted, sorted and vat'd.
Graham

TonyBurns

iTrader: (3)

Having a free flowing exhaust will increase your boost, the failsafe built into your ecu will detect this and cut it before it causes any damage to your engine, this will be obtainable from around 4k rpm where your max boost comes on line.
I would suggest either getting a remap to cope with this or getting a boost controller to stop it going above the maximum limit imposed by your ecu.

Tony

911

Tony is dead right. The fuel-cut appeared even when I had the standard STi exhaust on the car, and the Magnex turbo back gave the same condition, just got there a bit quicker!
You can adjust the Blitz, but I think 1.2 bar is about right? (or can I go a bit more?)
Graham

Marky-San

did the self check and it came up with code 45 - boost soleniod. So I've sprayed that, and clean the MAF as well.

Will try it tomorrow.

The car I have is running 1.6bar. Dont think it has been wound up though, think this was the trial setting for the original 100 STI's.

Worst case, I just buy a Boost controller suppose.

911

1.6 bar was exactly the figure Power Eng measured on my car on their rolling road. Mervyn said this was BAD news on a stock STi, and he had seen it before.
I would like to know how you get on with the 3 wire solenoid. sounds like this is a good mod to do.
Graham.

stubee doo

my wrx is doing the same i have been told its gonna be one of the sensors on the engine so its going back to jap imports today to be cured its a nightmare when your taking a bend at high speed and it cuts out