rb25det wierd idle

[paulr33]

Hi everyone,

Tonight driving I would pull up at the lights clutch in, shift to nuteral and the revs would stay at 1300 (ish) and never drop to the normal idle point of 700 or 800. SO driving at around 80km/h in 5th, coming to a red light shift into 4th works fine, shift into 3rd works fine and shft in nuteral idle drops to 1300 and stays there until i take off. This happens and doesn't fix itself. So I get to the servo eventually and pull up. go into nuteral, handbrake on. the second i do that the revs go from 1300 to 700 and i get perfect idle. i turn my lights off and the apexi auto timer lights up with the a/f ratio correctly and it actually starts showing it, norally it just says --- and flashes red/green. i saw it go between 17.8, upto 18.1 and upto 20 and down to 17.xx and back up agian, so it seemed to read it fine and correctly, light would go green for a while, then red, and back to green. Until i turned the car off to get fuel.

Refuel and turn back on and the idle problem is gone and the auto timer doesnt show the af again, it hasnt showed the af for a about 9 months now, last time it did work like this it just "worked" by itself then vanished again when the power to the car was turned off. I havent adjusted any wiring or anything so im really confused

Has anyone seen wierd stuff like that before? I dont know if theres something about to die or its just the ecu being wierd. Never seen the idle problem before. Car has just passed 100,000ks and the timing belt was done at 94000

Any ideas would be great - Im getting a consult serial cable this week so Ill check ecu errors and stuff but any ideas would be cool as a start

[paulr33]

The problem occured again the other night (revs high, but no a/f ratio on the apexi timer). The revs would just stay at 1100 no matter what. I even tried to make the engine stall by coming up to a stop in 5th and just letting it go until it got to like 500rpm then clutch in, instant 1100rpm. if i turn aircon on 1400 odd and off again 1100. sometimes if i turn the series 2 spotlights off the idle would got back to 800 odd but not always only sometimes it would drop from 1100 to 800

i reset the ecu tonight and idle seems perfect at 720

Anyone else seen this wierd problems?

[paulr33]

anyone what the normal voltage should be? mine hovers around 15.2

[Steve]

Where is your TPS voltage set? It should be around the 0.48-0.50V mark. In range for throttle shut is 0.4 to 0.6V.

If it is too close to the point that indicates open (above 0.6v) it may be fluctuating and cause the engine to think you have applied accelerator.

It did it with mine.

[Steve]

oh, and the 15.2 isnt voltage, its AF ratio, or 15.2:1. Stoich is around 14.5, under boost will be from 11:1 (or less if stock) to around 12:1

During cruise, the car should run a bit lean (>14.5) as this is how it improves economy. But note, if your O2 sensor is old, it may well be giving false readings.

Oh, and the O2 sensor voltage is in range between 0.0 to 1.0V.

[paulr33]

not sure what the tps is currently, im getting a consult cable hopefully next week so will be able to post back then. The 15.2 is voltage from the apexi timer. the a/f is always --- and never works, its only ever worked twice. The o2 sensor is about 3 months old and i can see its values, goes from 0.00 to 0.20 odd and floats around there

[Steve]

Well, maybe the 15.2 is the charge voltage from the alternator? not sure.

the O2 sensor should go from over 0.9 to around 0.02/0.04V. If its not, something aint right.

[paulr33]

yeah im not sure where the voltage comes from but it sits near 15.2 and is green

i noticed today i had my keys in the iginition cos i was packing shit in the car and didnt want the doors to keep relocking by them selves so i had it on ACC and the auto timer was displaying a/f ration as "---" like it always friggin does

after about 10 minutes it decides to show the a/f ratio, ffs!!!!!!!!!!!

so i start the car, voltage goes to 15 again and no a/f anymore

is the battery making stuff angry?

[ltcree]

If it is 15+ volts that is way to high, sounds like a faulty voltage regulator on your alternator. If you have or can get a multimeter put it across your battery and see what your voltage is with can running and not. should be around 14V running depending what is on and 12V when not running. If it is 15V it could freak out a bunch of things.