High idle...

Swanny_UK · February 02, 2008, 12:21:50 PM

Guys,

Im getting a high idle on my \'95 FD. Its running stock twins with a street port, Apexi filters, Apexi PFC ECU and decat exhuast. I recently swapped a cracked boost pipe between the turbopack and intercooler, and also recently replaced the power steering/aircon belt.

I start it up and it\'ll fast idle at about 21-2200 rpm until it warms, then drops to 1800 and then to around 1400 before settling at about 1200rpm with a water temp of around 85 deg. If the engines under load, it\'ll sometimes hunt at about 1200rpm up and down say 100rpm. If I put the aircon on it hunts around but between 1200 and 1600rpm.
The PowerFC Commander shows the settings for fast idle to be 1200 and idle to be 850 with 900 for aircon on.

From the searches Ive done, the first thing to check seems to be the boost pipes, which I have done, but I\'m going to go over more thoroughly this weekend. I was wondering if the tightness of the PS/AC belt might affect this? - I havnt got the specialist tension tool it shows in the workshop manual, so had to tighten best guess, but im thinking it may be too tight.

Is there anything else I should check? one of the pipes to one of the solenoids int he \'rats nest\' perhaps? if so - which one?

a.tapos · February 02, 2008, 06:03:24 PM

hello mate,i had a similar prob with mine after i rebuilt it,cover the inlet port on the manifold and the engine should die,if it doesnt you have an air leak,if so use squirt parts cleaner or easy start around the manifold if you catch a leak the engine revs will drop,mine was throttle body gasket which was typically the only gasket i didnt remove,the other two things are the warm up system on the throttle body or the idle screw below the throttle body mite need adjusting as they do work loose especially the warm up lever,id check for a air leak first though mate.and let us know how you get on. :Thumbs-up

Swanny_UK · February 03, 2008, 01:37:35 PM

Quote from: a.taposhello mate,i had a similar prob with mine after i rebuilt it,cover the inlet port on the manifold and the engine should die,if it doesnt you have an air leak,if so use squirt parts cleaner or easy start around the manifold if you catch a leak the engine revs will drop,mine was throttle body gasket which was typically the only gasket i didnt remove,the other two things are the warm up system on the throttle body or the idle screw below the throttle body mite need adjusting as they do work loose especially the warm up lever,id check for a air leak first though mate.and let us know how you get on. :Thumbs-up

Okey doke - a which point do I cover the inlet though? Do i cover the pipe leading to the throttle body?

As for the easy start/parts cleaner - squirt where? Into the inlet manifold to see if vapour comes out?

Swanny_UK · February 03, 2008, 02:25:03 PM

Right - I removed the rubber boost pipe between the intercooler and inlet manifold. Started the engine and covered the end of the plastic pipe which leads to the throttle body. Despite visions of my hand being permanently stuck to it, I held it over until the engine sucked, spluttered and stalled. So - Im presuming that anything from that pipe to the engine is fine?

Swanny_UK · February 03, 2008, 02:51:25 PM

Ive tried adjusting the idle screw, and its at its minimum, it wont go any \'lower\'. The throttle body arm is at its furthest point, so its not that.

Where do I go next? Which bit is the warmup lever?

a.tapos · February 04, 2008, 12:00:50 AM

okay.doesnt sound like a leak then,as you look at the throttle body there is a coolant hose on the right going into it,this feeds a metal plunger below it as the engine warms the wax expands and pushes the lever at the end of the plunger down,when the car is cold and runningyou can move the lever yourself and feel it click,this will drop the idle,so when its hot the plunger pushes the lever and essentially takes it off a choke.so if you let the engine get hot the lever should have switched over you cn check his by moving it again with your finger,if it makes no difference it means its disengaged and is working.if the idle drops i suspect the plunger/wax is faulty.as for the idle screw make sure your checking the flat screw under the throttle body not just the throttle stop screw.i have heard of apexi pfc creating idle probs on singles so maybe worth plugging your standard ecu in.maybe woth trying another idle air control valve to as these go wrong on all cars.

Swanny_UK · February 04, 2008, 12:20:12 PM

Quote from: a.taposokay.doesnt sound like a leak then,as you look at the throttle body there is a coolant hose on the right going into it,this feeds a metal plunger below it as the engine warms the wax expands and pushes the lever at the end of the plunger down,when the car is cold and runningyou can move the lever yourself and feel it click,this will drop the idle,so when its hot the plunger pushes the lever and essentially takes it off a choke.so if you let the engine get hot the lever should have switched over you cn check his by moving it again with your finger,if it makes no difference it means its disengaged and is working.if the idle drops i suspect the plunger/wax is faulty.

Well the thing is it seems the wax plunger is working as when its cold and fast idles its at about 2100rpm, and then drops to 1200rpm when its warmed up. So its moving as the engine warms, but just in the wrong range.

Quote from: a.taposas for the idle screw make sure your checking the flat screw under the throttle body not just the throttle stop screw.i have heard of apexi pfc creating idle probs on singles so maybe worth plugging your standard ecu in.maybe woth trying another idle air control valve to as these go wrong on all cars.

Ah right - I think ive seen a picture, I\'ll have a look at that - i think I had a look at the throttle stop screw. Im also running stock twins, and I dont have my standard ECU.

As for the idle air control valve - good point i\'ll look into it.

Swanny_UK · February 04, 2008, 02:20:42 PM

Im currently going back around the induction system double and triple checking everything. Ive noticed a hole with an adjusting screw, on the bottom of the throttle body as you look at it on the bottom right hand side when the TB is on the engine.

...on this image its upside down, and the hole is above and slgihtly to the left of the single openning - below the coolant pipe. Anyone know what this is?

Swanny_UK · February 04, 2008, 02:27:02 PM

Quote from: Swanny_UKAnyone know what this is?

S\'ok - found out - its the air adjusting screw! ...now - what does that do? Does this alter the idle range? Theres a page on AutoZone which refers to it on older models...

I dont want to lean things out or otherwise mess up the fueling y\'see...

Swanny_UK · February 04, 2008, 02:41:48 PM

Well - just adjusted the air-adjusting screw, and while it did reduce the idle, it was only down to a 1900rpm fast idle when i turned it as far right as it would go. So - I moved it back to where it was before. So Im assuming I *must* have an air leak!

a.tapos · February 09, 2008, 06:32:56 PM

that is indeed the idle screw mate,how odd,id agree with air leak but youve already tested for that,maybe worth another lap with easy start,did this happen over night or after it was worked on,

a.tapos · February 09, 2008, 06:35:33 PM

id still be tempted to try a a idle air control valve,where abouts do you live

Swanny_UK · February 09, 2008, 06:57:54 PM

This is rather embarrising. Went to see Pip at WGT today, he was ace. He had a look and the throttle stop screw hard worked loose. Its something I\'d not even touched and I was sure was fine when I check it, but all is sorted now, it was a subtle adjustment.

Thanks ever so much for your help though a.tapos.