Bouncing Idle
 

hey guys, i have a problem with my 13b 6 port N/A, it stars fine and idles about at 1700, but then when the thermowax pushes the fast idle roller off the cam it steadily bounces between 900-600rpm. ive replaced the TB, rebuilt the new one (so i know nothing is sticking on it), adjusted the TPS acording to the FSM, checked out all the solenoid valves, relays, fuses, vacum, lines, electrical connections.
ive have also disconnected several things one at a time when the idle is bouncing, BAC, intake air thermosensor, ect
i have a fuel gauge on it and it reads correct pressure in all peramiters acording to the FSM.
ive have also changed the plugs, plug wires, oil, coolant and cleaned and oiled the K&N thats in it (but i might have to much oil on it).

has anyone had similar problems, or heard of similar problems?

o ya i identified the engine but the car is a 1990 GXL with 85xxx miles.

That kind of an idle problem is almost always a vacuum leak or a bad TPS.

hey thanks a lot. I suspected the tps but don't have an extra 200$ at the moment

vacum
 

i have a problem with a high/bouncy idle(if you read my post in the past)
the idle bounce made me instantly think vacumk leak, so i changed aws + gasket, bac + gasket, tb, oring on tb, all vacum lines, secondary injectors lower grommets and upper oring, gasketbetween dynamic chamber and uim,gasket between im and uim, the hoses for the aws and bac.
the only thing left that could cause a vacum leak,i think, is acv + gasket, primary injector lowwer grommets.
am i overlooking something else that couyld cause vacum leak?

1500 rpm idle
 

i now i have asked SEVERAL question on this subject, and learn every time
now starting my car coldit warms up at 3k rpm then drops to 1400-1600 and bounces evenly there. when the fast idle roller seperates from cam (i have verified because no dashpot instaled rght now)but when it warms enough and seperates the idle bounce stops and the idle settles at 1400, checked clearence between sidewall and throttle plates, BAC, TPS(and adjusted), AFM, AWS, intake thermosensor(AFM and engine), "burped" the coolant several times, changed all vacum lines all intake gaskets and orings, changed ECU's.

but nothing i have done will decrease the idle speed. :scratch:
someone please help me ive been trying to combat this for 3-4 months. :(

I've combined 3 of your threads on this. Rather than making new threads every time, just bump this thread with new info.

Adjust your throttle stop slightly. On NA throttle bodies the adjustment screw is going to be on the lower back side. It's not the easiest thing to adjust on NAs, but a mirror may help. Just don't turn it too much, since a partial turn will change idle speed by at least a few hundred RPM.

hey thanks, can i bump them or dose a moderator have to do it?

ive checked the resistance of several sensors a the ecu connector (female) they are the same as testing the sensor itself. is there a way to bench test my ECU?

per the FSM the gap between the wall and primary trottle valve should be .5-.7mm, i have mine at .6mm. simulating the thermowax seperating the cam from the roller, the primarty throttle valve closes but is open ~.2mm, and has a little pin hole through the valve, should the pin hole be there? should the prmary valve be completly closed at this point?

my fc does the same excact thing and i was told just to clean the vaccums. havnt gotten to it yet.

By bump I just mean reply to your own thread. The tech sections all have a "no bump" rule, but as long as you're posting something relevant it's fine.

There's no bench test for ECUs unfortunately.

The plates should never close completely, and the pin hole is normal. There's always a small amount of air that is allowed to bypass the throttle butterflies. You might be within the FSM spec for butterfly gap, but the bypass screw (top of TB) and BAC will also be working to allow more air through. I'd say unplug the BAC, dial the bypass screw all the way clockwise (closed), then warm the car up. Figure out what your baseline idle speed is going purely off the throttle butterflies. Adjust the throttle stop to bring it down it necessary, then tweak the bypass screw and plug the BAC back in. Make sure the intial set coupler is jumped before making adjustments. If it's not jumped, the ECU will attempt to adjust BAC duty cycle to compensate for RPM changes.

ill try that, but i cant get to the throtttle stop screw unless i take the TB off.

so there is no way to check if the ecu is bad other than various things not getting correct signal and changing the ecu for a "known" god one?

i adjusted the idle sto screw to let the lever a little more in.
and set the narrow range tps to 975ohms at rest while simulating the thermowax extending, then 1 of my secondary injectors was leaking from the o ring, so i cant test it untill those orings come.

but how long should it take for the thermowax plunger to seprate the roller from the cam on a cold start? mine takes 8+ minutes from a cold start just lettng it idle. :(

8 mins. at idle sounds normal to me. It takes awhile before the idle speed drops all the way down.

after getting a new intake air themosensor my car runs much better but still not 100%. it will fall below ~1500to about 550 (im pretty sure that is cause i moved the throttle stop screw to let the buttefly close more) but the idle bounce is gone.

im having trouble adjsting my TPS, i have the two led mazda tester. let the car warm, grounded the initial set coupler, plug the tester in and turned the ignition on. turn the adjusting screw all the way cclockwise, no lghts, turn it clockwise~10 turns, green light only. and the green light only will stay on the complete travel ofthe adjusting screw, never red? might that inicate anything?

I've never liked the two light method. It always gave me odd results, so I set the TPS by voltage. The top pin on the plug should be set to 1.0V with the engine fully warm. Just back probe the pin and ground the other lead from the multimeter.

im not following?, there is six pins 3 for each potetiometer.
im thinking you mean te top/rigt pin according t the fsm.

Nevermind, you have an S5 don't you? S4s only have the narrow range TPS, so it's a single plug w/ 3 wires.

You could still set the narrow range side to 1k Ohms. This link explains it, but for whatever reason the pictures disappeared: http://howto.globalvicinity.com/gv_w...i=58&co=1&vi=1.

off subject but i have seen this website several times, but how come the pics never show up. do they for you?

Whoever was hosting the pictures took them down, or their access to some webspace was lost etc...

ive fixed everything i can so that the ecu only throw code 32(switching solenoid).
will the switching solenoid sytem not working cause the engine to run/idle wrong? ive checked, per FSM, the solenoid, continuity through solenoid , when i put a 9v battery on the connector for the solenoid and read the voltage at the ecu connection and it read ~1.5v(with the ecu disconnected of course)

my license is revoked for another month so im not driving it daily, just through my gated neighborhood for test drives. does the engine require some kind of break in period after messing with all i have?

also could somthing not be working right enough to hinder the engine oporation but not tell the ecu a code?

The switching solenoid just switches the air path from the exhaust ports to the split air pipe and vice-versa. I think the default is the exhaust ports, which is where most of the work is done anyway. The split air pipe is fairly useless actually. The solenoid has nothing to do with idle or engine performance. It's just part of the emissions system.

The S5 codes are a lot more extensive than S4s, so I think Mazda covered all the sensors/electronics pretty wells.

thanks, more knowledge!
but do you know if my car should be run normally for a while to get the adjustments and some new parts time to "settle in"?

hey bring your car by and ill help you out :) im out in gilbert

Vaccums, then check out your ignition coils/spark plugs.

after figuring out how to acess the idle stop screw(dashpot removed and long, skinny, flexible screwdriver) i started the car to warm it up, and noticed the usual light smoke at startup was very thick this time! so im thinking i should just rebuild the engine soon.
when warm and idleing the ~200rpm bounce is back(but the car didnt do it in the warm up stage...?) the bounce starts at ~100 and gradually increases the amount of bounce till ~600. i assume this is a vacum leak but have never seen a engines idle bounce increase so evenly?

if i rig a party smoke machine to pinpoint vacuum leaks, do you know if the smoke residue will harm any sensors or the engine itself or anything?