pilch

Guys (and gals)

One last ditch attempt at finding the fault in my MY94 WRX before I go completely mad (some people would say thats too late!)

I have codes 33 and 24, which are the speed sensor 2 and idle air control solenoid respectively. A while ago my turbo intercooler hose festered and I burnt a coil. Since that I have had a PE test and have a (great!) 263bhp @ 6333rpm. It also hesitates when I rev from idle, dipping slightly to almost 0. When I get the Engine Warning light on I can drop the clutch and the light goes out at 500rpm, but with a chance of stalling.
I run on Ron98 and have a magnex 6x4 oval BB and DTA Blitz TDV. I will replace the TDV with the original. I am pulling 10psi normal, 12psi max, dropping to -10psi at idle.
Any guesses?

Ta. pilch

Bob Rawle

Do mean that you have a Blitz dump valve fitted ? If so this could well be part of the problem so reverting to the original is worth a try. External bov's can play some cars up.

Bob

GavinP

Pilch,

It sounds like you already suspect the BOV may be the problem - and Bob seems to agree.

Out of interest, what does "Speed Sensor 2" measure ?

Thanks

Gavin

pilch

Bob, Gav, thanks. I'm waiting for the original TDV to arrive so I can exchange back. There was no (noticable) performance increase anyway.

Gavin; I suspect it measures speed! TBH I dunno. I can't even pinpoint it in my engine. I used

GavinP

Pilch,

Sorry to hear your continuing woes...

In the back of the Possum Link manual there is a couple of diagrams highlighting where each of the sensors are - see

Bob Rawle

Link manual refers to MY99 cars but is roughly right for the early ones, pictorially not quite right though.

Bob

pilch

Gav, I will check this against my engine. Don't suppose either of you know the WRX 94 layout?? How about a way of testing the unit?

Thanks so much for help so far

Dr Hu

Speed Sensor 2 is in the gearbox. (gulp!!!)

It checks the gearbox speed against speed sensor 1 which is built into the speedo head unit, so the ECU always knows how fast the vehicle is travelling and what gear you're in roughly.

Idle air solenoid valve thingy is the big valve affair cast into the inlet manifold, this opens and shuts the valve to adjust air in the inlet manifold at idle to allow the ECU to adjust idle speed, and fast idle when cold etc.

On early cars (Legacy's especially) these valve's used to get all carbon'ed up and then stick causing cutting out, poor idling etc, the easiest way to clean it (apart from strip down) is the pull off the big black hose going into it when engine is running (only slightly though or engine will stop!) and spray in lots of carb cleaner through a straw, this will get sucked through the valve and in theory clean away the carbon, the engine revs will rise, when you spray the VERY volatile liquid in so don't worry!!, use as much as half a can to make sure its clean!

These valves are tres expensive new!!!!!!!

Your problen sounds like a very weak mixture/air leak into induction manifold when you blip the throttle, check you have no hoses leaking, could be the idle valve stuck open (unlikely) or the dump valve stuck open pulling in outside air.

Hope you don't have to take G'box out

You haven't had a clutch in recently and not reconnected speed sensor 2 wiring by any chance??????

All I can suggest - hope it helps.....

pilch

Dr Hu,

Cheers for the info (gulp!!). Yes, I did have a clutch fitted recently. I didn't do it myself, I got a garage to do it. Not a Scooby place tho'. Where is the connector for the sensor? Could I reconnect myself? Would this cause the light to come on permanently? Then again, why am I getting throttle 'dip'? This is probably the AF ratio due to idle air valve sticking, as you say. Which hose is the idle hose? I could strip a box down to clean it manually, but don't like the idea of messing with the manifold!

pilch

Dr Hu

Pilch,

I'm not entirely sure, but I reckon you should have two connections into the gearbox, one for the reverse lamp switch and the other for the sensor, just jack up the car (ramp even better) and look around for any wiring connectors by the gearbox, there's plenty of space around Sub g'boxes so should'nt be too bad. But you may be right, if the sensor wasn't connected, you'd almost certainly get the check light all the time as you ignition on, as it does a sensor check.

I'm also not sure what the WRX layout is for the idle air valve, do you know where there is a good picture of a WRX engine bay on the web which I can look at and point you in the right direction, I know that later cars havent got the external hoses as it was all cast into the manifold, whether your WRX is like this I don't know. It will have a grey box on top with about 4 wires going into it, the box is adjustable, to set the ISC figure in the SELECT MONITOR, mark it before you remove it!! - the grey box is just the stepper motor, the actual valve is below it, never taken one off aso don't know how it comes apart for cleaning, but probably a snap ring or similar.

Most engine fault codes are caused by bad wiring, check the large multiblock connectors by the battery,(they get overspill from the handily placed washerbottle!!) break them apart, and make sure none of the pins or sockets are manky, spray with WD40 and reconnect, if you've ever had the ECU out, check the connections there as well (passenger footwell).

These type of faults are a bugger to find, but really it's coming down to giving it to a specialist with the diagnostic equipment to find the faults - feeling rich..........?

firefox

Pilch...

Drop me a mail... I will try and help you...

I have dismantled gearboxs and idle valves...most things actually.. lol

I will try and tell u where the sensors are... and stuff...

Cheers,

J.

pilch

Dr Hu and all,

I found the ISC and adjusted it. Another problem solved so far, but still not the error code! The idle is now more accurate (dropping to just about 1K then levelling at 1K). There is now no real chance of stalling.
I also removed the inlet valve from the manifold/intercooler and cleaned it. So much coke in there! Engine now feels more responsive and more gutsy. Still have error codes.
Now I only get code 24 when idling along through town at 2.5K revs and -10psi. After a minute or so the light comes on, then keeps returning when I drop revs to clear it. I think there must still be a AF ratio problem at idle (hence error code!) Considering buying a Blitz conical AF 'to solve the problem The missus wouldn't like me spending 'our' money otherwise! Reckon that will solve the problem?

pilch

Dr Hu

Pilch,

I don't think a new air filter is going to fix your error codes.....I take it you're still running the standard filter box & Air flow sensor?? - The other thing to try is to spray the air flow sensor wire with carb cleaner to clean any muck off it, don't worry the aerosol won't damage it.

Adjusting the ISC has probably just masked the problem as idle should really be about 750-800 rpm not 1k as yours is now.

This actually could be a faulty ISC motor/valve, don't suppose you have access to another for testing purposes?, as I know these are megabucks to buy new.

Could also be a faulty/dirty air flow sensor as mentioned above.

Good luck, getting your hands dirty I see!!!!

pilch

Dr Y

Yup, very dirty! All very well telling me what it could be... BUT WHERE IS IT!??? Bloody engines today are too complicated <grumble> Seriously, what and where is it I should clean/check/replace?

Cheers

GavinP

Pilch,

The AFM can be found as follows:

From the air filter box, follow the pipe rightwards until you see a black cylinder with some wires plugged into it.

You need to unplug the wires and remove the black cylinder from the car.

Inside the cylinder is the AFM.

IHTH

Thanks

Gavin

pilch

Gav,

Thanks mate. I shall check this at lunchtime