scoobyster

Hello All

I had some problems with my MY95 GL after cleaning the engine with CD2 and hosing. These were discussed in this thread, and seemed to be resolved after drying everything out and resetting the ECU (which had been throwing error codes for the 4 injectors, the idle air control valve, and the throttle position sensor).

The car runs smoothly and as normal in driving at all times now, the only problem is the idle speed varies. Around half of the time it goes to its usual 700rpm, but often it will stick at around 1100rpm before gradually coming down to normal (usually over a period of a minute or two, but sometimes suddenly, and sometimes it refuses to come down to normal). A few times the idle has stuck up at around 2000rpm, usually after a period of hard driving some way into a long journey.

ECU diagnostic checks still give the all clear and have done ever since the original reset. In fact I never got a CEL light even after the engine clean.

What should I do then folks? MAF seems to be the answer to most idle related issues on here, but usually when running rough. Disconnecting the MAF while the engine is running stops the engine still.

Can I discount the idle air control valve and throttle position sensor seen as they are no longer showing errors to the ECU?

Any advice would be much appreciated.

Cheers,

Ben

scoobyster

Anyone with any advice to offer?

Also, does anyone know if the MAF sensor from a MY95 1.6GL is the same as a MAF sensor from anything else? I believe they're different for N/As and Turbos, but are they the same for all phase 1 N/As for example?

On the MAF housing it says:

22680 AA170
AFH70 01
3910
Hitatchi

Cheers,

Ben

disoy

I have been getting the same thing resently, so i too would be interested in a solution.

Dark Blue Mark

ISCV and TPS faults can often occur in pairs from my experience. If one goes faulty, the other can try and comabt it, resulting in a fault. The ISCV can be cleaned by squirting cleaner into the air inlet pipe on the top, with the engine running. Bit tricky as it will stall if you let too much air in. You can also take the lid off it and check the spindle is free to turn. It should be very free. You need to mark the bolts on the top, as it must go back in the same position, as these, are used to adjust the idle.

The TPS is best checked with a testmeter, or select monitor. when closed it should show 0.5v (plus or minus 0.5) and 5v open (plus or minus 0.5) You can check it with a testmeter by taking the plug off it, and setting the testmeter to Ohms. Use the middle pin as ground and the outer plug on the turbo side to take the signal. Again, should read 0-5.

It should also be linear throughout the throttle travel. If its a faulty, you cant repair / clean it, and will need a new one.

Maf's normally give erratic idle, not sticking at high revs. Would suspect the ISCV need cleaning, or the TPS is shot.

MB

scoobyster

Many thanks for the reply MB.
Could you clarify I have the right idea about doing these tests? I have a feeling from your description that I might have the wrong idea about where the idle air control valve actually is.

In the pic below, is the part marked pink the IACV/ISCV bit that I need to remove? i.e. I'd need to undo the two screws on the flange and pull the ISCV away to the left? Where would I squirt cleaner, and would it be brake pad cleaner that I should use?

And is the bit coloured in red the plug for the throttle position sensor?



Thanks again for your help.

Cheers,

Ben

Jamie_B

After switching the iginition off and then on again does it idle correctly?

scoobyster

It will idle correctly for a while after switching on and off, yes. But the fault it intermittent anyway so it's quite hard to tell. Also at the end of a journey I try to let it idle long enough to eventually go back to the normal level so as not to have problems starting with a flooded engine.

I forgot to mention that the ECU reset fixed it for a couple of short journeys. The problem returned on a long journey, it had been fine for 70 miles on the motorway, but as only a few miles into a spirited run up the Snake Pass the problem returned.
It hasn't had any long journeys since, only up to 10 miles, but the problem now occurs around half of the time.

I'll try to experiment with switching off and on again and give a more definitive answer. What are your thoughts Jamie?

Cheers,

Ben

Jamie_B

I have a similar problem, its idles at around 1000 rpm after a spirited run. If I switch the iginition off and then on again it idles correctly.

I've had both the maf and lambda checked and they appear to be ok. I was also told that there were a few spurious error codes and so they did an ecu reset.

It seemed to behave fine for a couple of weeks, but now its returned.

Dark Blue Mark

Jamie, again, possibly a sticky ISCV, try cleaning it.

Ben, im not familiar with the layout of your particulat car, but the bit you've highlighted is the throttle pos sensor. The bolt either side is used for the adjustment of the sensor body, to adjust the voltage when the throttle is closed.

ake a pic further to the right and down a bit, and you should see the ISCV. On turbo cars, it has A B C written on the lid, and has a cream coloured lid on it.

MB

scoobyster

Thanks again MB.
Could you point me in the right direction on these pics? I'll ask on ImprezaSport.net too seen as they'll be more familiar with the N/A engine layout. I can't spot the ISCV following your description, may well just be missing it though. I know the part number is different for the turbos though so it might be a completely different layout.



And a view of the whole engine:


Cheers,

Ben

Dark Blue Mark

Ta for the pics. Ill have to pass im afraid, as I cant see it on there. Let me know how you get on.



This was when my engine bay was a bit dirty but the ISCV is on the bottom right of the intercooler.

MB

Dark Blue Mark

PS, trace the pipe coming vertically off the inlet of my air box, next to the coolant tank, it goes parralel with the I/C and into the top of the ISCV.

MB

vulnax999

iTrader: (7)

So THATS the ICSV... been looking for that!. Took the top off it, strong magnets in there I found when removing, but could not see what to clean?? Do I need to pull something out from under the cream cap??
MY94 WRX wagon if that makes any difference?

TA

V

scoobyster

Many thanks for the pic MB. I'd gladly swap you my clean engine for your dirty one

I still can't find my ISCV, but have been given a link to a screenshot of the workshop manual for a MY02 N/A 2.0. http://users.pandora.be/impreza/GX/i...r-cs-valve.doc
The bit labeled as IACV looks similar to what you identified as my throttle position sensor.

Will keep you updated, many thanks for the advice.

I'm going to try to get my suspension geometry done done at scoobyclinic soon so hopefully I'll get to pick their brains and get them to show me around under the bonnet if I don't have it sorted by then.

Cheers,

Ben

Jamie_B

Thanks DBM,

I've already had the ISCV cleaned and it did seem to improve for a while,but now the probs returned.

It's odd that after a spirited run it idles @ 1200rpm and you can hear the solenoid clicking loudly, but if you then switch off the ignition for a couple of secs and restart its fine or a while??

Looks like I'm going to have to get the garage to take a look at it again.