HKS dump valve
 

Andy,
I have the HKS Dump valve, so I screwed the nut at the back of the dump valve as closed as it would go, which I assumed did.......... or almost closed it completely, just in case it was a bit loose and leaking air somehow whilst normal driving,
however it didn't seem to make much difference to my normal driving as I still had the jerkiness, I didn't try any high boost driving as thats not really an issue.
If and when I find the fault.......to get back to top boost pressures should I release it a bit back to the middle setting or should I do that now ??

Cheers Kev

Tensioning up the spring or limiting the opening will have no effect on the issue you are having. This is something that alters the transient response on a maf based ECU due to its influence on the airflow back and forth across the maf.
You have a map based ECU so even a badly leaking dump valve would have no effect during the conditions you mention.
If, as i suspect, your GEMS does not have the air temperature compensation set up correctly then the 'jerkiness' is likely to be a mapping issue. It is possible for the car to run fine when mapped but then appear to go 'off' some time later when the intake temperature/humidity/atmospheric pressure has changed.
This can also explain the bad starting when partially warmed up.

cheers

Andy

Have I saved myself a fortune ??????????????
 

Thankyou Andy I hope your right,
I don't really want to start buying crank sensor, cam sensor, air idle valve, coilpacks etc etc,

Hopefully will meet Simon next Wednesday and all will be revealed,
I will post any results next Wednesday night.

Does that mean everyone out there with a gems/motec should get it mapped for summer, then winter conditions ??????????????

Cheers everyone...............................I think I'm still married,


Kev

With the exception of some Link units, most of the speed density ECU's do have 'proper' temperature compensation but not all of them have it set up, er, proper ;)
A maf based ECU is much better at covering up mapping issues which could cause hesitations on a map based unit, this is due to the maf measuring the actual mass of air entering the engine instead of calculating it from the pressure and temp sensors. On the map based systems there can also be heat soak issues affecting the air temp sensor and this can make issues worse.

Andy

Just looked in the maps I have hear of your car Kev and Air Comp and Air Adv Comp tables all look sensible but will be the first place I look when get the laptop on the car.

Blocking off the vac line on my car always stopped it dumping but take note that with higher boost that might not be the case.

Cheers
Simon

Idle problem as well!
 

Hello Kev, long time no see.

Interesting too read your thread, apart from a decat my car is pretty standard. However since a couple of hard drives a couple of months ago I to am plagued by a poor idle. Coming to a head yesterday when it failed an emissions test. They thrashed the engine hoping to clear the high CO reading to no avail. Since however the idle has got worse, dropping to 0rpm on the rev counter and stalling occasionally. There are tell-tale puffs of black exhaust smoke while it is 'hunting' @ idle.

I have today... Had Mike Riv confirm my thoughts leading to the ISCV however I have...

R&R Cleaned the oxy sensor

R&R Cleaned out the throttle housing

R&R Cleaned out the idle speed control valve

R&R Cleaned & gapped the S/Plugs ( by the way any gap less than .7mm is criminal)

R&R All HT leads and made sure all connections are good.

Gave the car another thrashing, too no avail. Even my old CO meter is showing a high figure. Probably why it's using so much jungle lately.

Is your mixture rich??? or are you over fuelling???

I've boxed mine for the night I will have another look tomorrow. A faulty temp sensor can fool the ECU into thinking the engine is still cold, therefore enrichening the fuel mixture when not needed.

All the best,

Dave

Kev,

A idle control valve can probably be had from Grade A for about £35.

It may also be worth checking the potentiometer on the throttle position switch. If this is failing it may be unlinear and confusing the ECU.

In most cases the throttle potentiometer spends most of it's life at half/light throttle, so this is where is is likley to get worn out.

You can measure it with a standard multimeter. Unplug it an connect accross the pins so that you see the varying resistance as you open and close the throttle. Then open and close it very slowley to check it's linear and that there are no sudden jumps or drops in resistance.

Simon may evenbe able to check this with the GEM's software (if it's worth it's salt).

Hello mate
 

Dave
From my little knowledge and what I am constantly learning, can I just check have you got a MAF sensor ?
As this is first thing people seem to check?
If that is faulty, then your ECU is not reading the correct air flow, therefore your ECU is over fuelling ????????????????

I can't really tell if my car is running rich or not, having no cats etc etc,
I can always smell petrol at the back of my car, can't say I've noticed any black smoke.

Cheers mate
Kev

A little closer perhaps ?????????
 

I was contacted by Steve Simpson today and after a discussion he believed it pointed towards the Throttle position sensor. If this is faulty then it would explain the kangerooing on normal drive, but getting better under boost,

I'm presumming the incorrect message is being sent to my GEMS therefore the mixtures would be out.

To all the stupid people out there like myself, this is the black square box, as you look into your engine bay on the left handside of the manifold, where the samco hose between the top mount intercooler meets the manifold, it has three wires coming out the top of it, this is connected to the butterfly inside the manifold. It is not the air idle valve on the other side, which on my car is a beige colour.

Again this can be looked at by Simon next Wednesday on the laptop, and hopefully can be played with the map, Steve very kindly said we can phone him on Wednesday and hopefully their two great minds will come together...and I'll just be the stupid looking one in the corner listening :D

I think thats it for now, its very strange that you can buy a GEMS ecu, a so called after market upgrade (and pay a fair bit) yet it cannot bring up fault codes when something goes wrong, like a bog standard ecu that comes with the car, oh well,
Kev.

I would check the water temp sensor. When mine failed it would be intermittant, driving fine, then all of a sudden cough and splutter on cruise, then idle @ 1700 revs, then die when on boost. Then can't restart if turned off. All the hallmarks of a failing water temp sensor. BTW the gauge in the dash comes from a seperate sensor and will look fine, but the ECU is getting the wrong signal (thinks its very cold so runs very rich)

Give it a try

Cheers
 

Would this show up on Simons laptop when it gets plugged in, if this was faulty, I'm trying to hang on spending any MORE money, before Wednesday ??

Kev

SNAP :):) not sure if you saw my post. But those are were my thoughts too....

When mapped the coolant temp sensor was normal..
could have failed since but unlikely.

First place to look on Wednesday :)

THANK F*CK ITS SORTED
 

Well after a visit to Barretts, Canterbury, for an oil change, and some other bits, (and also taking RB5108 to collect his car.................read all about it in projects :))
We both made our way to the services around the corner to meet Simon aka Jolly green monster at eight o'clock.
Bryan was sorting his running in map, as he had changed injectors from 480 to 550, (kindly sorted by Mark Agin :) )

Then onto my car, when first looking at the map, we went straight to the throttle position sensor area. Straight away Simon tweaked it to a lower setting, I went for a little drive and the difference straight away was obvious. I still had a slight hesitation so he lowered the setting again.

Now I know he will explain later, but I think the problem was the ECU was being told the Throttle position sensor was closed, whilst still driving, therefore asking the air idle valve to cut in...........as if idling..........therefore lowering the fueling............but of course I'm still driving.......so hence the fuel was a lot less causing my severe hesitation.
I think thats it :) but I could be wrong !!!!!!!!!!!!!!!

Anyway all I can say is my car is hitting 1.5 bar and it f*cking pulls superbly,
I'm glad I didn't have to buy any sensors etc etc
Now for the rolling road I've been promising myself to finally find out what my car is producing :D

PS Thankyou to Simon for staying to midnight to sort both cars out, sorry to the people in the caravans trying to sleep.....................................nah not really :D

Snap, BIG thanks to Simon roll on next friday........give me some boost :D:


WOO WOO :) :) :)

Oh, you need a louder exhaust....

lol.. for some reason I got no notify on a reply here.. anyway..

Pretty much as you said Kev.

From memory the throttle possition sensor was dropping to 7 when foot off the throttle but the TPS Min was set to 16.. so you were able to drive it on light throttle at 11 I was seeing for example and the ecu was trying to swap to idle valve etc..
lowered it slightly and things improved.

It was no problem..

lol @ people in the caravans..

Simon