cab idle problems..again

[richrx]

Hi

my FC cab has another idle problem ... ive used the search facility but i cant find any similar problems. Any hints on where to start would help.. im almost tempted to strip as much as possible off and have a play, its just TOO COLD!!

so here it goes...

Basicly the car starts and runs as normal when its cold and the engine settles into an 800rpm smooth idle when the water temp comes upto normal. However after aproximetly 5 minutes the idle will drop to 100 rpm, before the ecu will kick the revs to 1500rpm to stop it stalling, the revs drop again to 100 rpm before being kicked up... and this continues untill it finally stalls.

its not overheating, going by the stock water gauge at least.

i\'ll pull the plugs and put in new ones/clean them up.

and i\'ll go round the bay with wd40 looking for any air leeks too, but i dont think it\'ll be this as it seems to idle fine for a period, and the symptoms would relate to a large leak.

it almost seems to mis behave when the oil comes upto temp, or this may be a coincidence.

has anyone had anything similar, or any systems to start on?


thanks

Richard

[m1tch]

Have you had a look at the BAC valve, it is responsible for the idle and is heated by the coolant, which changes between hot and cold, ie when its cold it has a higher idle (seemily \'normal\' idle on startup) and then reduces idle from the high idle to normal idle when its warmed up. In your case, high idle seems to be normal idle and normal idle seems to be stalling if you get what I mean.

I know that the BAC valve can get gummed up and stuck, but there is an idle screw that you can tweek which might be your first port of call unless you have already tried that?

[Prof]

That sounds like a really exagerated case of TPS adjustment being out.  When the TPS is out it works like this:
 
It thinks the revs are too high for the throttle position, so it cuts fuel, this brings the revs crashing down - the ecu detects this and then stops the fuel cut - sending the revs back up again and the cycle repeats.
 
Nornally you see this behavior after the initial warmup higher revving phase, as the was pellet device keeps the plates open and the revs up until the water warms up enough for the wax device to shut the throtle plates.  If the TPS is out, it will start to oscillate - usually around 1500 rpm until the system is fully warm, where it should find a stable idle.
 
If the TPS is badly out - it could be doing this when it should be stable idle.
 
I\'f you\'ve checked for obvious vac leaks, then this is the next thing to set - it means warming up the engine thouroughly to set it - which is going to be fun in this freezing cold weather - may need to keep your foot on the gas a little.  Engine doesn\'t need to be running to set TPS - just warmed up.

[richrx]

ive got a spare bac valve lying around so i\'ll clean it up and put it on tomorrow!

i\'ll get the TPS adjusted, correct me if im wrong, but to set it you bend it slightly? is that correct?

i also forgot to mention there is a ticking noise comming from under the intercooler... i dont know what the ticking thing does but if you take the intercooler off, it sits on the intercooler bracket on the right hand side((standing at the radiator looking towards the windscreen) just to the right of 4 or 5 multi coloured check valves i think). not sure if that makes sense :s

thanks for the quick replies though :Thumbsup!


thanks

richard

[Prof]

Hi Rich,
 
TPS Adjustment - there is a small screw with a spring on it - that\'s underneath the intercooler and behind the alternator. You can see it if you look thrugh the gap there.
 
Basically it adjusts the position of the TPS sensor relative to the throttle position. Most adjustments should be made there - but it\'s possible the thing is so far out that you may need to adjust it by moving the hole throttle positon sensor using the 2 screws and giving it a jiggle - but that\'s an intercooler off job for sure.
 
There are various methods for adjusting it - but the one most of us seem to find works best is to measure the resistance of the narrow range sensor on the 2 wires along one side of the 6 way plug. You are looking for approx 1K on them (it means unplugging that 6 way connector). From memory one of the wires is green - but if you follow the narrow range sensor - you can identify that by the fact that when you operate the throttle by hand, one of the sensors completey disengages from the throttle assembly - there is no contact - that one is the narrow range - the one that always stays in contact (the one towards the back of the engine) is the full range. Anyway, 2 of the wires from the narrow range sensor go to pins on the short side of the 6 way plug - it those you measure.
 
I can post up pics when I get into the garage again - maybe a day or two.
 
Oh - by the way - that clicking thing - if it\'s on the oil filler neck - it\'s the stock boost solenoid.

[dthebuk]

I had a similar problem with my old Egi. Prof and mitch seem to have put up a good bit of info but here\'s my original thread, it may help.

http://www.mazdarotaryclub.com/forums/showthread.php?t=52610

hope you sort it

[pdtaylor18]

Remember to adjust the TPS when the engine is hot and then adjust idle when its hot. The two are very closely related.

[Adam fc]

im suffering from something simular at the moment,interested to see how u get on.

[richrx]

still not had a chance to check this out yet my headlights stopped working!

luckily it was the exact symtoms of Grinders and the fault is only 8v going to the switch!

so this thread http://mazdarotaryclub.com/forums/showthread.php?t=32221 had been a god send! great info. just to clarify, you take the new feed from the cold side of the 30a fuse and wire it to the switch?

(i thinks its time to get my full membership paid! too much great info!)

thanks

Richard