Impreza stalling issue pos vac leak ? Please read
 

I've spent the last two days trying to locate what I think is a vacume leak on my 99 type r without success ... Basicly the symptoms are : when I start the car it idles fine when I give it some gas the rev's go up as per normal when I release the pedal and revs drop but keeps dropping to the point of where its going to cut out and on accasions dose stall.

I'm now at a loss at what to do I've tried pressures testing and spraying soapy water, but cannot find anything , I've tried spraying brake cleaner in areas where I think the leak is without any noticeable diffrence in idle.

I've recently changed the maf ( about 1 month ago ) I have a apexi pfc in place with a maf reading of 104 so I no it's good but can u still get good readings and the maf be dirty ?? I've also changed the lambda sensor and icv recently so they can all be ruled out, I dose suppose the apexi has a vacume reading ??

I really don't what to have to pay a fortune for a smoke test but I guess I will have to but thought I would throw it out on the site first and see if anyone had any ideas b4 I shell stupid money at a garage..

Many thanks

On the V4 when I cleaned the ICV I noticed the screws holes are slotted that hold the unit in place meaning it can be adjusted, I marked mine to get it back in the right place. Don't know if it's the same on your car. Fuel filter dirty blocked injectors might be worth looking at mate.

Hi, the icv on the v5 / 6 is different to the 3/4 it can only go in on 1 position so its not adjustable.. :(

Make sure you've checked all vacuum hoses on the inlet manifold after the throttle body. Failing that check all hoses between the MAF and the heads, so that's all the connections on the turbo inlet hose, hoses to boost controller, hoses on the back of the intercooler. Check the gaskets on the intercooler and the inlet manifold / throttle body also. Check the PCV hoses are properly connected under the intercooler too. Sounds like you've done quite a lot of that though... long shot but you could try disconnecting the brake booster hose and plugging it on the inlet manifold to see if there is a leak on that path somewhere.

Failing that might also be worth doing a compression test, and if that comes back ok then a leakdown test to rule out rings. Alternatively take your oil filler cap off and then rev the engine, if it throws out VISIBLE exhaust smoke then that is also a pointer toward possible ring sealing issues.

Only other thing I can think of is a fuelling issue, so maybe swap your FPR for a known good one (assuming you are not using an OE FPR that is) and check the vacuum line to the FPR also.

Thanks for that nullfork ... I took the intercooler off yesterday had a good look over it and couldn't see anything suspect. Also took of the hard intake pipe with air intake on all is solid and sealed up.
I'm gonna take another peak later see what I can find but I'm not holding my breath.

Could u explaine what u meant by disconnecting the brake booster hose and putting on the inlet ... What is the brake booster hose ?

Cheers

Should be on the top right of the inlet manifold, quite a large bore hose that runs eventually runs under the intercooler and toward the master cylinder. I was suggesting taking that hose off the inlet manifold and then plugging the spiggot on the inlet manifold that the hose came off. That way you can rule out a leak along the brake booster pipework. It is a long shot though as I've never heard of it being a problem before, just thought I'd list all possibilities that I know of - sort of process of elimination.

I've been there chap, spent weeks on and off checking idle with new alcatek ecu update and found out I had two issues, one was the ICV had a sticking point, it would rotate okay-ish but then odd occasion it would stick. I cleaned it twice and lubricated it twice, until the thing would spin 100% free. I also found my FPR had a leak so I sealed the air nipple and the screw thread with sealant. Idle is so much better now and I did have your stalling issue and also sometimes revs stuck higher than they should be (suspect that's when ICV sticks). I used a vac gauge to test all the pipework that attaches to manifold, this for me was the big step forward. Wasted 3rd of a tank in testing stages.

I had a idle issue only a month ago where it would idle at a stupidly high rpm and then drop and go bk up again etc. I bought another icv which solved the problem, then the lambda sensor on my apexi wasn't reading so replaced that now this I'm at my whits end with it ! On top of that the maf I had to replace as it was on its way out according to the apexi. :( just seems to be one thing after another but I will get it back to its best I refuse to be beaten !

What year impreza do u have ?

Thanks nullfork ... Yep I no what u mean about it been a process of elimination I'm really just thinking I'm gonna have to bite the bullet and get it smoke tested as I just cannot find what the issue is. I do all pretty much all my own work but I guess when somthing like this pops up unjust don't have a choice. :cry:

Are you running a dump valve? I had symptoms simular to yours when the spring broke in my dv. Looked fine from the outside with no leaks but would try to stall at junctions. Blanked the dv off and the problem disapeared. Opened the dv up and found the broken spring.

Yes I have a dv .. The car was mapped with a forge dv in place since then I have changed to a Turbosmart dv. I thought this may have been the issue but I swapped them back over and it made no diffrence :(

Booked car in for the weekend to have the smoke test done :( not looking forward to the bill will keep the thread updated

Thanks every1