Little help needed

[mickey&me]

Hi guys

wondering if anyone can help. I am having problems with my Super S, while the car is cold the revs are about 1k but after a few minutes it drops to 750-800 after the car is warm. then 30 secs later it drops to 250rpm and just about to stall when it automatically brings the rev back up again to 800. this cycle continues! it idles ok then drops then automatically comes back up again... only under no load.

while under load the car is fine, but when slowing down its at around 250rpm and stalls with i brake to a stop... she starts straight away tho..

other info i have found is that when under no load the exhaust system is popping.. like pop, pop, pop quickly while engine is running.

I have changed the t/b with another spare one that i re soldered but still the same.

Any ideas?

 

[tomwest]

what modification work have you done to the engine? air filter/back box/increased fuel pressure?

ive wound my fuel pressure up and discovered it "pops and bangs" from no throttle to back on throttle.

i would suspect the throttle body as prime target. if the cold start idle adjust has broken you need a new throttle body, or at least a second hand one off a good runner. the thing has a thermowax element, and if the casing were to crack while hot, some of the wax could escape. after this, the car could start normally, but when heating up, the revs would drop off too quickly, and too far.

 

[mickey&me]

I have two t/b.. one i re-soldered and the other is from a 89k engine

mods so far are the n15 airbox, the t/b i resoldered.. thats it on the engine side except a jun flywheel and new clutch which was installed before Christmas... all the rest of the mods are cosmetic..

i have tried both t/b's but its the same problem.. so either both of them are gone or that aint that problem?!?

got anything that i can try to test t/b's?

Thanks Tomwest

 

[tomwest]

the only thing i can think might help you out is to increase the idle, essentially by shortening it. theres an adjuster on the t/b. it will lift idle, but but it should stop the motor dipping so low in the revs

i dont think there will be a problem with the throttle body, it wouldnt make sense of it.

my understanding of this situation is that the engine isn't sensing the drop in revs. multi-point fuel injection (as seen on micras!) dont put fuel in off throttle, to increase economy. the ecu re-introduces some fuel to stop it stalling when it reaches the level it considers to be idle.

i would guess that yours is confusing itself and forgetting its already near idle.

hope ive been some help!

 

[frank]

good old antistall system eh fwn works fine on a stock engine (apart from the high idle if you coast in neutral).
but fit some mods and it has a mind of its own lol mine was always hunting up and down for no apparent reason, then would run fine for days, i gave up in the end, and binned mine last year

 

[pollyp]

it should idle 1400rpm cold and 750rpm fully warmed up.

normally with a warmed engine when the ecu senses the revs gone above 1k, the IAV opens and idles at 1k shortly after closing the throttle.
now at that point if the speedo is below 5mph or ur in neutral, the IAV would close 2sec later and idle drops back to 750.
if ur above 5mph and in gear the IAV stays open and continues idling at 1k

i suggest first warm up the engine to 80c, adjust the hex idle screw behind TB till it idle at least 750rpm, check the timings at 15deg. if not, turn dizzy till its 15deg, readjust idle screw to 750rpm and recheck timing.

once correct, let engine cool down fully cold, restart and it should cold idle at 1400rpm

 

[mickey&me]

Thanks guys

pollyp, ill try your step by step when i get a chance and ill report back

frank, you removed the anti-stall system? how did you do that? if my problem still occurs i might just ask you how to remove it too.

 

[frank]

frank, you removed the anti-stall system? how did you do that? if my problem still occurs i might just ask you how to remove it too.

took it off mate then blocked the 2 ports, but bear in mind i have no PAS etc, and my alternator runs at 1/2 speed (bigger pulley)
so my parasitic loads are very small, and need no idle correction, and i have a little lever under the steering column that gives a fast idle first thing in the morning

 

[tomwest]

took it off mate then blocked the 2 ports, but bear in mind i have no PAS etc, and my alternator runs at 1/2 speed (bigger pulley)
so my parasitic loads are very small, and need no idle correction, and i have a little lever under the steering column that gives a fast idle first thing in the morning

like this Frank!

 

[LastVenue]

Did you sort out this problem mickey&me? I've got the same thing happening to mine.