Mazda Rotary Club

Hi all. I\'ve been having idle issue for some time now. To try and help the fueling and timing of the car I have just purchased a Knight-sports ECU (Cheers Pete). The Ecu is good as Pete ran it in his car but in mine I am still having idleing problems. Without changing anything other than the ECU the car started and reved but would not hold a constant RPM and the RPM was very low so the car stalled. I have had a play with the BAC valve to try and smooth it out a bit and I can now keep the car running, But the idle is still hunting. Is there a way to adjust the screw on the UIM without taking the intercooler off? (Im not sure of the position of the screw). Also the car is overfueling even more than it was, big bangs and flames when on over-run:Giggle but could this be a cause of the idle issues?

This is a video of the car as it is now. Hope it helps.

Taking the IC off isnt that much of a job; however I can;t recall wether or not the TII has the adjustment screw on top of the throttle body like an EGi does?

Yeah I know its not a big job to take the intercooler off but how do I know what to set the screw to without the car running. Will I have to remove the intercooler, turn the screw a bit, re-fit the intercooler and try it untill I get it right?
I was hoping to be able to get to the screw without removing the intercooler so I can do it with the car running.

Turn the screw counterclockwise on the BAC valve (sorry dont have a picture) and try starting it again, alternatively get a mate to do it whilst you play with the throttle. Had to do this on mine as it wouldn\'t idle

The ECU did not overfuel or flamed........which it had though !!!  So something on your car is making it more pronounced.
The BAC valve might be worth taking off, have you checked the resistance values of the BAC ? There is an adjuster on the top of the throttle housing you can adjust, think it might be the one on the front, might also be worth checking the TPS and that the throttle cable is adjusted correctly.  I would be reluctant to adjust the throttle just yet as it might only mask another problem.  I do have another ECU you can try but the knightsports worked well in my UK S5 and JDM project car.  The idle did drop with the knioghtsports in but that was adjusted by the idle adjuster in the BAC.
Question is when did this start to happen and what have you done to date ?
Have you a cat?
running air pump ?

Been shifting through a lot of archive stuff and all seem to point to a vacuum leak of some sort,might be worth taking the UIM off and having a look. U can also check out the injector seals at the same time, they can cause this. been trying to buy some for a while but not having much luck without paying a silly price in shipping costs.

try this:  http://www.teamfc3s.org/info/articles/idle.html

I\'m thinking it might be the TPS or a vacuum leak after reading that. luckily I have a doner car which I can pinch bits from! I have already replaced the BAC valve and it was check when I put it on. The car ran fine when I bought it around 15 months ago and I haven\'t altered the intake or exhaust or really anything to be honest. Its been pretty trouble free till now, I can even live with it but its just not how it was when I bought it. I like it to be perfect. I know thats a bit much to ask but it just goes to show how good this car can be.
Where abouts is the TPS located?

TPS on the top of the UIM on the front of it,has two electrical connectors. You will have to make yourself a little 2 bulb connector. Works really well. I used two LEDS but going to use standard bulbs as they were more like little strobes which did not work too well.

Wow thanks for that Pete. looks like i\'ve found myself another job for the weekend!

Ok just had a look around the engine for Vac leaks and can\'t see anything obvious. So know i am thinking TPS is the next thing to check. But I have now noticed that when I come to a stop and the car is idleing/hunting around 500rpm if I put my foot on the clutch, the revs rise to a smooth 750-800 rpm. Any ideas what thats all about? If I can get it to do that all the time I\'ll be happy!

you are prob taking the load off the engine when you dip the clutch - so the revs will rise ( i think ?? )

Quote from: grinder;505302you are prob taking the load off the engine when you dip the clutch - so the revs will rise ( i think ?? )

With my S5 it idles at 750-800 and when i select first it increases to exactly 1k revs, it perplexed rotechnics when prof took his car to them as it does the same thing so it might just be a setting in the ECU that does that?

not sure how it affects the rotary vac system but we used to spray instant start around manifolds and certain vac lines, if the revs rise then you have a leak, however our vac lines go through check valves and the like so not sure what the consequences might be. Some holes though are just pin size ones and you may never find them.  Unless you are sure that all have been replaced it will only take an hour to replace them all, I would have a look at your injector seals as well as every single one I have removed the seals have been hard and very loose within the housing. They will squash down a bit but not a lot. I have sealed mine in with a bit of black sealant as extra security. Must admit my idle is not that good, mine starts perfect but when i select any gear when its cold it goes all lumpy, put the clutch down and i get no diference, just as soon as i engage gear. When its hot it behaves itself. Going to look at the switch on the gearbox. I disconnected the rear ones (4 wires) so will pull the front one next.

This table might give a clue - it\'s the input to output table - what sensors affect what outputs Neutral and Clutch seem to affect quite a few
 
I know when you start the car out of neutral (foot on clutch ;)) it will disable the AWS/ASV solenoids (they are wired in parallel, so it\'s really only 1 output) which is the circuit that revs the nuts off the car when you first start it to warm up the cat (which most of us don\'t have anymore).
 
I\'ve noticed the rev change when I select first as well, so I am guessing this is the neutral switch or clutch switch - and may be some kind of preload launch thing built into the ECU.
 
The PRC solenoid is tied to the IAT sensor and provides higher fuel pressure on a warm start - that might effect rev\'s in that way - may test this by unplugging the solenoid  - but that should only operate on starting - it\'s defeated after about 60s as is the AWS/ASV rev up code.
 
I know the relief/split and port solenoids are tied into the revs and clutch/reverse/5th switch, but I no longer have these and still have the rev increase on selecting 1st gear.
 
Defo needs further investigation...

Ok now your just confusing me! You guys really have a wealth of knowledge haven\'t you. Let me test the TPS and have a better look at the vac lines before I go any further.

I think Dave\'s piece was more geared towards my problem but in a way just another piece of the jigsaw in everything concerned with the idle.
Hope the TPS check goes ok, its fairly easy and defo worth doing before anything else.

Quote from: Prof;505552This table might give a clue - it\'s the input to output table - what sensors affect what outputs Neutral and Clutch seem to affect quite a few
 
I know when you start the car out of neutral (foot on clutch ;)) it will disable the AWS/ASV solenoids (they are wired in parallel, so it\'s really only 1 output) which is the circuit that revs the nuts off the car when you first start it to warm up the cat (which most of us don\'t have anymore).
 
I\'ve noticed the rev change when I select first as well, so I am guessing this is the neutral switch or clutch switch - and may be some kind of preload launch thing built into the ECU.
 
The PRC solenoid is tied to the IAT sensor and provides higher fuel pressure on a warm start - that might effect rev\'s in that way - may test this by unplugging the solenoid  - but that should only operate on starting - it\'s defeated after about 60s as is the AWS/ASV rev up code.
 
I know the relief/split and port solenoids are tied into the revs and clutch/reverse/5th switch, but I no longer have these and still have the rev increase on selecting 1st gear.
 
Defo needs further investigation...

Here\'s one thats going to mess with you-
I\'ve removed all of the solenoids and emissions stuff and the original engine loom and ecu (gone Microtech) and pressing the clutch pedal down STILL effects idle... lol

And TPS is causing me idle probs too at the moment, as it relies on the voltage from the battery to tell the ecu what the throttle position is (and the voltage seems to keep changing every time I run it) I spend most times adjusting the TPS reading.

One thing I\'ve noticed is that when the oil level is lower on the dip stick the idle seems to hunt more.  Topping up the oil so that you are between 2/3rd\'s and Full seems to help with the idle - no idea why?
 
Does anyone know how often the TPS goes out of adjustment ?

Hi Adrian,

I fitted my Blitz ecu on mine no idle probs at all... Then developed a fault with my omp and blew a power trans in my Blitz ecu:mad: Since changed the omp and ecu to a RE Amemiya and that is idling low sometimes stalling. Have\'nt had the chance to have a look at it, but I suspect tps. You will have to rig up a test light to do though mate.

Well some good news finally. I got round to removing the TPS off my donner car at the weekend. So decided to fit it on monday night. I took the intercooler off only to realize that I had left my 1/4 drive socket set at work, and couldn\'t remove the TPS cause you can\'t get a spanner in. Gutted. The UIM around the TPS was generally covered in oxidisation and muck so moved it by hand a few times to make sure it was all free. I replaced the intercooler and fired up the engine to make sure I had no leaky pipes. Only to be greeted with a lovely purr from the engine at about 1200 rpm. HHHMMMM I thought reaching for the BAC valve screw. Sure enough after a couple of turns she was purring like a kitten at 750 rpm and not hunting in the slightest :). Shes been running like that for a couple of days now so I am hoping that is the end of it.
Except she doesn\'t do the 3000 rpm cold start thing its more like 2000rpm then dropping to 1500 rpm but I can live with that.

maybe then a sticky TPS? or maybe a leak from the intercooler and you just never spotted it?  Main thing is that it works. My idle is fine now as well but still hunts a bit until its warm. Not got round to adjusting/checking the TPS but that cured it last time.