Stevie_h

Hi i am experiencing some hesitation with my 03 sti. It has the tsl333 pack on it, but i dont think this is the problem. The problem is this, if you hold partial throttle, instead of pulling smoothly the car will miss and hesitate. All this happens between 1500rpm - 4000rpm. Once the car is fully on boost it pulls fine. If the car is on full throttle, it pulls fine. The ecu is not throwing any codes, but i suspect that one of the sensors (suspect O2) is ending its useful life and is getting slow to react. I have already changed the plugs and checked the gaps on them. On a rolling road power run the car made full power 334bhp. So really this problem effects drivability more than performance. Can anyone offer any insight?
Other than changing out sensors one by one, what approach to diagnostics could be taken to confirm that sensors are operating correctly?

Thanks

Steve

DeanF

iTrader: (1)

Steve,

I am suffering the same at the moment 2001 Sti, If i gun it through the gears (WOT) its fine, But if you accelerate gently (light throttle)it does it, It's not a misfire, more like holding back, or someone applying an engine brake etc, or retarding the timing. I suspect the O2 sensors also, so will be looking at these shortly. The One before the up-pipe looks a right Barstool to get out !!

Dean

p1ggm

i had a similar problem, and it was caused by the dump valve, so i have a standard one on atm, i have stripped down the aftermarket one and cleaned it all up so i am going to try it on again

Stevie_h

Dean, your description perfectly describes my symptons.

steve

DeanF

iTrader: (1)

I will let you know how i get on then, Or Vice Versa if you sort it before me.Thanks

Dean

Reg P

Hi,
I've just logged on to investigate the same thing, I run an 03 Sti fitted with the Prodrive kit. My car runs fine on full throttle, but when I'm accelerating gradually in the higher gears, 4th, 5th and 6th, between 2500 rpm and 3000rpm, my car "stutters". It seems to be getting worse although it still appears to be intermittant. It's in for a service next week and I tried to book it in for the fault to be checked. I go the standard "we'll plug it into the computer and check the fault codes", which doesn't fill me with confidence. I will keep you posted if I get any feedback on this but I'm keen to find out if these are the same symtoms you guys are experiencing. It's only starting doing it the last couple of months by the way!

Reg P

Stevie_h

My car is going in to get looked at tomorrow. I hope they find it.

Ste

DeanF

iTrader: (1)

Cheers,
let me know then Steve.
Thanks
Dean

ScoobyDawg

Hello

I've got the same problem with 1998 JDM WRX Type-R.

I'll be taking the knock sensor off this weekend to clean it and put it back on followed by an ECU reset.

I suspected my MAF and cleaned it - still the same.

I my clean the 3 point selenoid and check the Sensor on the down pipe and headers.

Please let us know what you do to your car, to clear the problem.

Cheers

Dawg

KenS55STI

I have a similar thing on my MY01 STI. It surges during acceleration with part throttle, through the gears is fine and so is full throttle. On the motorway it is worst, say pulling into the next lane to overtake. Boost gauge shows boost going up and down. The possible explanation I had from Andy F is that the aftermarket decat exhaust is causing the boost solenoid to over react and the solutions are to either fit a bigger restrictor to the boost pipe or have it remapped. I haven't had the fault codes read so don't know if there is a sensor gone. The garage that look after the car said they have only had one car of that MY with the problem and it was caused by bad fuel but I can rule this out on mine because I have used a lot of fuel since.

I'm planning to have the fault codes read and get a remap at some point, although I may change the exhaust first because it is quite loud on the motorway which is where most of my miles get clocked up.

unfeasablylargegonads

iTrader: (3)

A friend had the same problem casued by an aftermarket dump valve. One of the springs in it was not strong enough and it leaked air at low RPM

DeanF

iTrader: (1)

How did you go on then Steve ???? Any Joy ?????

StephenPope

I have the TSL 333 on my MY04 STI and it is mucking fagic!!! If I were you, I would contact TSL - as you no doubt know they are very helpful and knowledgable. Good luck.

ZEN Performance

It sounds like compressor surge, or possibly a leaking (or just plain crap vent to atmosphere) dump valve.

Is the hesitation accompanied by a "chuffing" sound?

Paul

DeanF

iTrader: (1)

Paul,

The Dump valve is standard, Only Mods are a centre section & Backbox, It feels almost as if boost is being taken away & then corrected !!!
Cheers

Dean

ZEN Performance

i was replying to Stevie's initial query, sorry.

Sounds like partial throttle boost issues, probably causing compressor surge at the same time. Exhaust changes can affect this, and 2001 maps are not the best it has to be said, later standard maps are far more refined, and the ECUs have better control of boost on the whole.

Paul

DeanF

iTrader: (1)

Paul,
It's Ok Apologies not needed. What is compressor surge ?? Spinning up to soon ?? Would a 3 port boost solenoid help control this, or is a remap the only true solution or maybe a later Ecu Etc ??
Thanks for your help.
Dean

Stevie_h

No joy i am afraid! I had the voltages from the sensors checked and they all seemed fine. Prosport were reluctant to spend to much time on it (so as not to run up a bill) until they had ruled out a problem with the map, so they recommend Richard Bulmer have a look at it.

Cheers

Steve

Stevie_h

Hi, i dont have a aftermarket dump valve fitted.

Ste

Stevie_h

For me the problem is only noticable between 1800rpm and 3500rpm. I assume the car is not on boost for most of this rev range. Puzzling!!!

stev

DeanF

iTrader: (1)

Taken from, Impreza Newage Modifications - Engine Stage 1 - Part 1 . Re. SURGE
http://bbs.scoobynet.co.uk/showthread.php?t=462807

Good news first…… we achieved 360bhp!!!!! Unfortunately that was the only real good news, as it was evident that this latest batch of modifications caused some severe problems with surge (or what certainly seemed like it).

TEST4 had previously highlighted this issue but now it was even more evident, so further investigation was required.

The surge appeared between approximately 3000-4000 rpm and from 4000 rpm onwards it disappeared. This was both extremely audiable from both inside and outside the car, which sounded very similar to you trying to breath in through your mouth nearly closed and then quickly moving your tongue backwards and forwards from the opening (sounds weird, but gives the same audio effect). While looking at the boost gauge as the car was being run on the rolling road, it showed the boost very rapidly fluctuating around the boost target through this same rev range and then settling from approximately 4000 rpm onwards.

So what was causing it?!?!

As previously mentioned, the RCM Induction Kit even with the standard sized MAF pipe caused similar issues, so it was a fair bet that it was something around the induction kit. Perhaps with this 80mm MAF pipe together with the non restrictive inlet pipe making it even worse. Whether or not it was worse was a side issue….. the important thing was trying to find out how to eradicate it.

Surge is not a good thing to have, as not only does it not sound very good, it hampers the boost stabilisation and can have a detrimental effect on Turbo life.

For background information, Surge is caused by the inability for the engine to consume the air produced by the Turbo at a given point. Normally (obviously dependant on amount of air and at what rpm the Surge happens) the engine can consume the increased air further up the rev range, as the engines cams and valve usage increases allowing more air to be consumed. When Surge occurs, the Turbo compressor produces more air than the engine can consume, which causes a backup of air at the intake which actually creates reverse-flowing pressure waves that can be very damaging to the turbo.

The immediate conclusion was that the increased diameter MAF pipe and non restrictive inlet pipe had allowed for a bigger increase in airflow, based on the reasons why Surge happens. The same conclusion could then be derived from TEST4, even though the Surge was not as bad it was still apparent and was obviously caused by increased airflow, even though it was still the standard MAF pipe size (68mm) and standard inlet pipe.

The only way we would allow the car to run, was to try and decrease or eliminate the Surge. Although perhaps seemingly meaningless, we decided to try and map around this issue, rather than taking specific parts back off as it was important to try and learn more form the current issues. The only way around this was to cap the boost between 3000-4000 rpm to approximately 1bar, with normal previous boost targets from thereafter.

Upon running the car on the rolling road the Surge was greatly reduced, but still slightly apparent. As with any testing, we were prepared to leave the slight Surge issue to see what effects the whole of this issue had on both the car itself while being run in normal road conditions.

dan rolfe

This is the same sorta problem that ive got to be honest, hesitation at low revs and general pick up but also ive noticed that the revs dont drop between spirited gear changes even when the car is properly warmed up. Dan

DeanF

iTrader: (1)

bump

Stevie_h

I am having someone else look at the car on tuesday night for a second opinion.

steve

DeanF

iTrader: (1)

Steve.

It would be nice if they could put there finger on something !! Im off on Fri afternoon for a looking at session

Lets hope between us we find / sort something as it dampens what would be a V Good driving experience !!!

Dean

~DrEaM~

please post if the problem is solved, as i got the same problem

Stevie_h

Update:

The car has been running much better since monday. The only thing that has changed is that since monday i have been driving it to work (nice long spirited run), whereas up until then the missus was using it as a daily driver to go to the shops etc, until i sold my WRX (which went on saturday) Therefore driving the car properly has definatly helped the issue. Anyway i took it to a specailist last night (www.cotcomp.com) and got the car connected to Delta Dash. Tried as we might we could only get it to hesitate once or twice and even then it was hardly noticable. The car checked out perfectly on all counts except for one........ The battery voltage was a little low and the alternator duty cycle was not behaving as expected(always on i think), all suggesting that the battery was on its way out.. This fits in with the fact that occassionally when i crank it first thing in the morning the alarm has let out a minor chirp and when i was fitting some ICE a few weeks ago the battery ran flat very quickly.
So its a long shot, but voltage fluctuations from a less than healthy battery may be the cause. I will get a new battery at the weekend and test the theory.

Ste..

woolz

mine doing this aswel..

DeanF

iTrader: (1)

DeanF

iTrader: (1)

Well went to get mine checked out & they came up with nothing. There was a Historical Primary Lambda fault. That was cycling at a standstill & they said it was a little slow, So what it would be like under load !! Who knows.
I will be purchasing a new one as it has done 47,000 miles In a hope that this helps.

Dean