FC3S help - high hunting idle + fouling plugs

[yasiryassin]

hi everyone,

a few weeks ago my FC started acting up.
 
background story
during the recent snow i took the fc out for some sideways action. during that night i stopped the car once, and it struggled to start up. the next morning the car wouldnt start at all.

took out the plugs and they were black as coal. so cleaned them up and car started to run again.

however spark plugs are constantly getting fouled everytime it is driven. and struggles to start up. I have new plugs bought but dont want to put them in yet until i figure out whats going on.

since that - the idle has now had become way higher at 2k on idle. was previously just under 1k.

so got a 2nd hand throttle body, cleaned it up and got it put on.
bought a new TPS from mazda, think i set it correctly. as was told when bought the car these would need replaced.

now the idle is around 1.5k, but when warms up it will go hunting.
 
i hooked up a timing gun and found that one of my trailing coils is not firing. so 2nd hand coil pack bought but just waiting on it arriving. and bought new leads, again just waiting for them to arrive.
The spark plug to this corresponding coil is the only plug that isnt fouling for obvious reasons.

my questions
how do i lower the idle?? firstly because i want the high hunting idle fixed lol, and secondly i want the idle down so i can check the timing, to see if thats whats fouling the plugs.

the BAC valve on my car is blanked off, so that can be adjusted.
and i cant seem to find a picture of the idle control screw anywhere. been searching loads but no one seems to have a picture to show what screw to turn.

if anyone could give me some advise it would be much appreciated,
cheers Yas

[yasiryassin]

also i decided to test the injectors to see if they were leaking or clogged, never done this before. so spent all day today figuring out what the hell to do lol.
took out the primary injectors and they didnt seem to be leaking or clogged. i youtubed how to videos and managed to make a simple set up to test them.

they seemed fine so i didnt bother with the secondary injectors.

[yasiryassin]

wee clip of the car idling when up to temp.
and a quick look at the intercooler pipe - makes working on TPS easier

http://img689.imageshack.us/img689/3527/e1qkjjitqquadbflwatrck.mp4
 
the idle surg stops if the TPS is deconnected. but i have set the TPS and it is within correct range, check and reset several times. just cant get it to stop surging. and idle will remain high with TPS out.
 
from what im find online - the idle is controled by the BAC (which mine is blanked off) and the throttle body stop screw ( which mine isnt actually interfering with the throttle!

[the hat]

With looking at the throttle body spindle in the pic it\'s not somethingbsilly like the throttle cable is too tight and holding throttle open slightly

[yasiryassin]

unfortunatly not that simples

the car will rev low if you ride the clutch in gear. so the cables defo not holding the throttle up. i also checked and theres slack on the cable.

even with the throttle cable not attached, thats is where that screw will sit. it is just turned so much to not interfer with the idle/ cause high idle.

will try clean the MAF senor next and see if that makes a difference.

[richrx]

Hi

 Think the plugs may be fouling up and going black because there well beyond there best, this happened to me with my turbo 2, the plugs were black to I cleaned them up. Next day they were black again. It was sorted by the new plugs.

The idle sounds like the tps needs adjusted, 10 minute job and should sort the idle out.

Thats my monies worth

RIch

[richrx]

Sorry just noticed the TPS has been set, how did you do this? With the engine running or with a voltmeter?

Rich

[yasiryassin]

the spark plugs were newish, less than 1000 miles. so i dont wanna stick in the new ones when engine still not running well as dont want new ones to foul up and waste more money.
 
i set the tps with a multimeter. took car for a 10 min run to get up to temp. then tried setting it by 2 methods - testing resisitance in the narrow range - engine off, and then testing voltage in the narrow range with the car switched on, but not with engine running.

resistance i got it to 1k ohm.
voltage method got close to 1 v.
 
im pretty sure im setting it properly, as have read many "how to" threads on rx forums.
 
had a quick check for vac leaks but couldnt find any obvious. was spraying carb cleaner to see if revs would drop during the idle phase where the idle woulnt surge. the surging only starts when the cars up to temp.
i tried to do an inhouse smoke test for vac leaks also lol, but didnt show anything

[yasiryassin]

not much input on this thread lol, but for those interested i figured out what was wrong today

coolant passage in the throttle body was blocked. so that was messing everything up! so i cleaned it out, and adjusted the cold engine idle so that it doesnt work.
 
so i had to screw the idle control thingy out a bit to sustain revs. and re adjust tps.

got the idle to below 1k, not the smoothest idle, however hopefully this will change when i stick the new plugs and wires in.

noticed coolant leaking from some of the small hoses around the upper manifold so had to stop work to allow the pressure in the coolant system to go away.

plan
change plugs, wires, try fix coolant leaks. then see what the timing is like.
 
so if anyone has high hunting idle issues, and are sure TPS is set correct and no vacuum leaks. id advise to look into the coolant passages in the throttle body.

[TiddlesRX7]

Well done finding the problem. Idle issues on these can be a major PITA. Good to know this fault for future!


Ade

[jimmydanny]

I would stick a BAC on again. When I got a BAC on my S5, albeit a S4 N/A one (without idle adjustment) I got much smoother idle. Worth mentioning my throttle valves are shut 100% so I can\'t idle without the BAC. I got the idle down by putting a jubilee clamp over the hose and just screwing till the idle was where I want it. Steady at 800 now, no hunting at all.

[yasiryassin]

stuck the BAC back on, the idle hunts a bit. so maybe need to adjust TPS and the BAC valve screw a bit to get it 100%
 
however i have now got another problem.
car drives fine and producing power throughout the rev range. however on very light throttle, say when just coasting. the engine sounds awful, as if its running on one rotor. then if i press the throttle more, it will run fine.
this happening with new spark plugs and wires. i think the spark plugs are still fouling as it sometimes doesnt start up well and needs rev\'d up to start running both rotors smoothly.
 
just wondering id anyone else experiences this during partial throttle?
im thinking i must have a fueling issue?
 
cheers,
Yas

[Prof]

I was going to say without the BAC you\'ll have trouble adjusting the idle down to 750 and stable.   But with it on, you have to go round the loop of adjust idle, warm up engine, adjust tps, adjust idle, and so on.  When you get as close as you can - then adjust your timing - the leading pulley mark off either of the plug leads ( they both fire at the same time on the front coil pack as it\'s wasted spark) needs to line up with the pin on the front housing - undo the 10mm locking nut on the cas and twist it to alter the timing.  You\'ll find the trailing timing should be spot on - 2nd mark on the pulley - lines up with the pin when you have the clamp on the front trailing plug.
 
The trailing coil pack cleans up the emissions and ensures a more complete combustion, but the car will run ok with the leading coil only.  However, the ECU has a feedback for the trailing coil so it will throw an error if it\'s not firing.
 
There is a wax pellet device on the throttle body, which gradually closed the throttle plates and sets the low idle when warm - you can adjust the stops for this setup on the back of the throttle body, but the main idle adjustment is the screw in the BAC valve and of course setting the TPS so it doesn\'t hunt - which it will do around 1500 rpm - that maybe where you are hitting rough running - gradually increase revs till you get to 1500 - if it\'s hunting there, the TPS still isn\'t right.  You can only set the TPS properly on a thoroughly warmed up engine - if you don\'t you\'ll be forever finding it needing setting!

[yasiryassin]

cool thanks prof!
yea i originally set the tps and idle with the throttle body stop screw, but the BAC was blocked off. the idle was quite low and the engine sounded like it was about the die while idling. checked and adjusted timing at that idle also.
was in the middle of tinker with the throttle body stop screw to get the idle set better, but the then neighbour came out and went ape :censored::censored::censored::censored: at me for making too much noise lol. so had to leave the idle low.
so stuck the BAC back on and the idle came up to 750ish, but hunts a tiny bit. like maybe hunting by up to 750 - 500.
im pretty sure the TPS was within range. but i guess i just need to re do the whole process again now the BAC is back on, and adjust that also.

cant work on the car much atm, have to wait till the granny beside me is out any time i want to run the car in the drive way lol. which seems to be never!