Intemittent high idle. Stock UK FD

[ianelvar]

Hi guys

She\'s running beautifully 400 miles after my rebuild, but I\'ve got one small problem with the idle that I just can\'t nail.

I can set it up all properly in diag mode to 750 revs, then take it out of diag mode and let the ECU do its idle thing and it\'ll settle down to it proper idle speed. However, if I rev the engine, it will settle back down to idling at about 1200 revs until its put in gear, at which point it\'ll settle down again.

It\'s not an air leak - it wouldn\'t be intermittent, and wouldn\'t settle down when put in gear. All hoses have been replaced and cable tied anyway.

I\'ve checked and double checked the TPS.

throttle cable isn\'t holding the butterflies open, it sits on the stop every time.

Reset ECU many times.

Only thing I\'ve just this minute thought of is clutch switch. Anyone got any other ideas? It\'s doing my head in.

[DR SCHNITZEL]

Have you tried unplugging the Iat? "black thing at the back of the UIM"
 
Also if the nut on the small thread at the front of the tb isnt tight that can cause problems as teh thread vibrates forwards as you drive and you will never get a stable idle.
 
It may not be either of these tho, good luck

[ianelvar]

Thanks bud. Nut\'s tight, but I\'ll se what it\'s like disconnecting the valve.

[DR SCHNITZEL]

You could try screwing that little nut away from the bit o metal it pushes on too say half a turn.

[ashc]

mine does this intermittently too, despite commander idle settings - i usually just press the aircon button, it goes higher still to about 1350 then settles right down again after a second or so when i switch the aircon off again. i have cleaned the tps and done all the idle testing things as you have, never found why it does it, i then decided it might be normal !!!!

[SmbFD3S]

Are you running standard ECU?  and is it doing it when hot or cold or both?

[ianelvar]

mine does this intermittently too, despite commander idle settings - i usually just press the aircon button, it goes higher still to about 1350 then settles right down again after a second or so when i switch the aircon off again. i have cleaned the tps and done all the idle testing things as you have, never found why it does it, i then decided it might be normal !!!!

That\'s interesting. It\'s a weird one - if I disconnect the idle valve so the ECU has no control over the idle, it still behaves the same way, so there\'s obviously something else going on. I checked some of the one-way check valves yesterday and found that most are leaking. Popped them apart, and a quick run over superglue round the joint and they\'re good as new. Didn\'t help the problem though.

It\'s like there\'s an intermittent vac leak, but it\'s going to be a bummer working out where.

Are you running standard ECU?  and is it doing it when hot or cold or both?

Yes, standard ECU. Seems like only when hot, but that could be because it\'s masked by the wax valve warmup. Why Mazda couldn\'t settle for the ECU hiking up the idle on warmup I\'ll never know. Most other manufacturers seem to manage just fine, rather than having another piece of kit in the idle loop.

[neil_jdmr]

When i was on the stock ecu i had a very similar idle and fixed it by accident really by blanking off the solenoid that prevents positive boost whilst the engine is cold, cant remember what the name for this sol was but that was its function.
 
Idled fine after that and i always give it a good 15-20 mins before any real boost anyway.
 
Get a pfc as the stock ecu is a POS anyway

[SmbFD3S]

Deffo sounds like something to do with the AWS system but not sure what.  I\'ve bypassed was valve as i\'ve removed the throttle body heater to help the inlet temps...
 
I would change the one way valves for the viton ones to be honest, react and hold much better than the originals....
 
You say you think it\'s a vacuum leak, but if it was it wouldn\'t settle down when you put the clutch in so it has to be ECU/Electronic related i\'d have though...
 
I remember when mine was stock and had the 3000rpm warm up until the water reached 50+ and then when hot it used to idle at around 800.  Started from hot it used to do as yours does but used to drop eventually in gear or out of gear.
 
Maybe it\'s just how it is on the UK cars?

[SmbFD3S]

When i was on the stock ecu i had a very similar idle and fixed it by accident really by blanking off the solenoid that prevents positive boost whilst the engine is cold, cant remember what the name for this sol was but that was its function.
 
Idled fine after that and i always give it a good 15-20 mins before any real boost anyway.
 
Get a pfc as the stock ecu is a POS anyway

His car is standard tho mate, and the standard UK ECU is actually pretty good and also has det protection which the Apexi doesn\'t.  Can also run on 95 RON fuel.....

[ianelvar]

Deffo sounds like something to do with the AWS system but not sure what.  I\'ve bypassed was valve as i\'ve removed the throttle body heater to help the inlet temps...
 
I would change the one way valves for the viton ones to be honest, react and hold much better than the originals....
 
You say you think it\'s a vacuum leak, but if it was it wouldn\'t settle down when you put the clutch in so it has to be ECU/Electronic related i\'d have though...
 
I remember when mine was stock and had the 3000rpm warm up until the water reached 50+ and then when hot it used to idle at around 800.  Started from hot it used to do as yours does but used to drop eventually in gear or out of gear.
 
Maybe it\'s just how it is on the UK cars?

It\'s a really funny one. It used to drop down when I popped it in gear. After I\'ve fiddled it now doesn\'t. I tried blaking off the double throttle too, which didn\'t help. I can move it manually while it\'s idling and it makes no difference.

I can now get it to idle fine for a while, rev it, have it drop back correctly. Rev it a bit harder, then it\'ll drop back then pick up again. Then after another blip it might or might not settle down.

One thing I did find was the second throttle butterflies (not the ones to stop boost on cold engine) didn\'t have their stop screw adjusted. It was just hanging in open space. I set that up and it got a whole load better. It\'s also less jumpy when driving going from closed throttle and back on, which is something.

If I disconnect the idle valve while it\'s revving high the revs die down a bit, but not to where they would if I disconnected while it\'s idling normally. Frustrating! Oh Yes! I can only assume there\'s another path air can take into the manifold, and it\'s taking it!

Maybe it is a UK thing, but it\'s definately weird if it is. I\'ll investigate some viton valves. Where can I get them?

Thanks for all the input so far guys.

[ianelvar]

I looked into the Accererated Warmup Valve too - the one that makes it rev its nuts off when started from cold. I can black the air feed to that right off and it makes no difference.

[ozzyvelcro]

I got my Viton valves from rx-7 guru on ebay took about a week from the states, send him a message and he\'ll put a buy it now up http://myworld.ebay.com/ebaymotors/rx-7guru/

[ianelvar]

:cheers I\'ll look into that

[ashc]

to be honest, mine isn\'t a problem to me really, i\'ve just come to expect it sometimes - my ratsnest has been fully vitoned and siliconed, and the airpump removed, and various blanking plates put in, i\'ve replaced, checked or cleaned all the solenoids - i think my problem is something electronic, for me probably tweaking of the pfc rev/idle/fuelcut settings - there is quite a lot on rx7club about it with the PFc. Doesn\'t help your problem with a standard ecu though, sorry!