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Impreza 1999 WRX won't idle


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Hi all.

1999 WRX with idling problem.

Only had the car about 2 weeks and i will admit it didn't run right when i got it. It had an issue where if you had a light throttle applied like around town or just cruising along there was no finesse to the accelerator and it was either on or off. If you put your foot down it would run fine but then if you back off it was as though the throttle was missing a position if you understand what i mean. So i put it down to the TPS being worn out. Also it was idling quite hi (around 1500-2000 revs). I then purchased a good second hand throttle body assembly of a running impreza that had been in a rear end crash. I drove the damaged car around the yard before pulling the throttle body assembly off and it drove fine. Fitted it to mine and the throttle light running position is now fixed. But now it doesn't idle at all. When i removed the throttle cable from my car i noticed it was tight and there was no slack so i am assuming someone had tighten the cable up to mask the idle issues.

There are no fault codes present. I have replaced the MAF (twice for new ones), Lambda sensor, cleaned and checked the IACV, changed and gapped the spark plugs and done ECU reset after each item has been replaced and gone for a long drive. The throttle body is also clean.

It just wont idle and it feels like its running rich as the spark plugs are black and sooty.

Any ideas as i cannot afford to pay extortionate garage costs and want to fix this myself.

Any help would be much appreciated.

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Now you've fixed the throttle issue (tps ) the faulty tps and tight throttle cable might have been masking other issues .


If iacv was off another scoob it could need adjusting ?


You could alter the idle by loosening the screws on the top of the iacv and twisting it slightly . Just make sure you mark the original position ,so it can be returned back if it doesnt work .



Could also be the ecu temp sender or its wiring / plug , give that a visual check . As if the car thinks its cold it will enrich the mixture


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Thanks for that. I checked the voltage at the TPS before I tried what you said and it was at .21v. I rotated it slowly each way and the engine note changed but didn't help the tickover. I've also changed the temp sender at the front of the engine last weekend. Is there another one I cannot see?

Ordered a new coilpack today (expensive son of a b###h) and HT  leads. 

Next is look at the fuel pump and fuel pressure regulator.  

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  • 1 month later...

How do.. noticed with interest your symptoms as I had pretty much the same on my s turbo Forester... (after approx 10 k miles after “sti” rebuild).. turned out a new shiny set of red ht leads from the land of the rising sun sorted it right out.. only after changing maf etc..!! Hopefully yours be flying now..!!

Sent from my iphone using Tapatalk

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  • 2 months later...

Check your vac lines is a defo had similar issues with mine and was the pipe on the back of the boost guage that was split .. ive found if it was leads or coil pack the car doesnt perform .. misfires and hesitation all day at full throttle ive experienced this to 

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