slow idle startup.
Discussion
Finishd putting car back together, not changed the engine timing at all. Now when I start the engine I need to use the accelerator, then it starts at about 300rpm and then over about a minute it creaps up to 800rpm, but no matter what I adjust etc, I cant get this behaviour to change. SO what would cause this? measured the fuel pressure its 36 psi, Tried another MAF and no change. According to Rover Gauge, the temp sensors are correct.
Whats RoverGauge telling you about the stepper position- 0 is closed, 180 is wide open and should correspond to around 2000 rpm if the air is getting through. To check the stepper is working, remove it, and then have a play with the stepper position with RoverGauge (engine stopped-ignition on) and see if the cone moves in and out. Dont go to a 0 setting, you may end up winding the cone out of the motor, and its sprung loaded so ping and its gone, or if you do at least put the stepper in a pot so you can catch the bits. Good way of getting its to bits to clean it!
blitzracing said:
Whats RoverGauge telling you about the stepper position- 0 is closed, 180 is wide open .
Idle bypass is about 75%. I tried removing the stepper and getting Rover gauge to control it and I can get it to move in and out. With the engine running, using rover gauge I can open and close the stepper and this causes the engine revs to rise and fall and then the ecu re-adjusts it.I think that it is over fueling as the exhaust is sooty, but the short term lambda is round 0.
Long term lambda is nearly -100% which I think indicates overfueling.
Fuel rail pressure is about 36psi with pump running dropping to about 30psi with pump off where it stays for at least 5 mins, so I don't think that any of the injectors are stuck open.
Just wondering now what is the next thing to go and look at / check.
Look at the fuel trims again- the readings are inverted as its a matter of trim- ie taking fuel away- so a + trim is removing fuel, a - ve trim is adding fuel. You will get a very high -ve trim value if you have an ignition fault- as it mistakes unburnt fuel for a lean mixture, so it adds fuel (or reduces the trim). Im trying to get the RoverGuage bods to change the values to "add" and "remove" fuel to clear that one up.
Edited by blitzracing on Monday 10th September 20:47
blitzracing said:
Look at the fule trims again- the readings are inverted as its a matter of trim- ie taking fuel away- so a + trim is removing fuel, a - ve trim is adding fuel. You will get a very high -ve trim value if you have an ignition fault- as it mistakes unburnt fuel for a lean mixture, so it adds fuel (or reduces the trim). Im trying to geet the RoverGuage bods to change the values to "add" and "remove" fuel to clear that one up.
Mark. I am somewhat dim. Always will be! but learning slowly. What is the RoverGauge? How useful and how is it used on the Stepper. Where can it be purchased? Thanks..............Eddie
Here is the rover gauge display when I had just started the engine. Maf reading looks good the temps look right.
Idle bypass is nearly fully open, but its ticking over at 559RPM target is 1122, also lambda is -100% so it must be chucking in fuel.
So I can only assume that the problem is on the ignition side and thus it thinks that it has a lean burn.
Id go for that, and its on both banks. Id get a strobe on each HT lead and check each lead in turn, also check the timing and spark advance. Ive seen level of correction on a car with Magnecors that was misfiring, but the engine was pretty rough as well, you could hear it missing. It cleared once we replaced the Magnecores. Also try unplugging the ECU for a while, (hot engine) and then monitor the long term fuel trim when you restart the engine- It should start at 0 % trim, and then start to correct at around 2 mins 15 seconds (hence the long term!) if it winds back to 100% you know the ECU is likely picking up un burnt fuel as lean.
Not got a couple of plug leads swapped or dizzy cap wrong????
Not got a couple of plug leads swapped or dizzy cap wrong????
Edited by blitzracing on Thursday 13th September 21:39
Edited by blitzracing on Thursday 13th September 21:42
Chris. Just had the same low idle requiring some throttle to start from cold, until I refilled with a tankful of fresh V Power fuel. The previous tankful was also V Power. Surprise, surprise! Now starts from cold without throttle and idles at 900. We have no control over the quality of the fuel.
Edited by EGB on Saturday 15th September 22:29
I have been putting in regular fuel as that is what I have always used, also it is all fresh.
Spent a bit of time today checking everything and having a good look and all seems OK, checked timing, continuity of lambda to ecu connections, ecu grounds etc. Unplugged the ecu whilst I did all the checks. Plugged in ecu and Rover Gauge. Long term and short term trim both 0. Started engine, short term stayed at 0 for 20 seconds and then over the next second it went to +100%. stayed like this until I switched the engine off a few seconds later. Started it again, short term lambda was 0 for 20 seconds and then went to +100%. I assume that +100% means mega lean. So possible that both lambdas are dead. ECU is duff, next I will try and measure the voltages from the lambda to see if they are really 0, ie lean or if they do switch and the ecu is not reading it correctly. During all this the tickover is still only 600rpm.
One thing that may or may not be related its that it takes about 15 seconds for the Rev counter in the car to register the rpm, the rev counter in Rover Gauge is instant so the ecu does know that the engine is running.
Spent a bit of time today checking everything and having a good look and all seems OK, checked timing, continuity of lambda to ecu connections, ecu grounds etc. Unplugged the ecu whilst I did all the checks. Plugged in ecu and Rover Gauge. Long term and short term trim both 0. Started engine, short term stayed at 0 for 20 seconds and then over the next second it went to +100%. stayed like this until I switched the engine off a few seconds later. Started it again, short term lambda was 0 for 20 seconds and then went to +100%. I assume that +100% means mega lean. So possible that both lambdas are dead. ECU is duff, next I will try and measure the voltages from the lambda to see if they are really 0, ie lean or if they do switch and the ecu is not reading it correctly. During all this the tickover is still only 600rpm.
One thing that may or may not be related its that it takes about 15 seconds for the Rev counter in the car to register the rpm, the rev counter in Rover Gauge is instant so the ecu does know that the engine is running.
So you have the ECU trying to remove fuel if the trim is +100. This should correspond to a lambda voltage of a volt or more showing a rich mixture, and its likely to be stuck, and not cycling. Its unlikely that the probes are not working, as you start with a zero trim when the probes are cold, and then as soon as they start working,and the voltage rises too high from the probe and you see the ECU trying to correct it with +100 % trim. Over fueling has limited options such as over high fuel pressure (missing vac pipe from the regulator?) A low temp reading from the engine, a or high AFM output. Try a simple test, and let some air into the plenum by loosening one of the blanking plugs (assuming you have one free) and just removing it it bit by bit letting in more and more air, and see if the trim starts cycling as the mixture leans off. This will prove if the basic ECU/ Lambda system is working.
I did a bit of googling today and found a couple of references to over fueling at tick over due to fuel pressure regulator. So put a gauge on the fuel rail and started the engine, 34 psi, blipping the throttle made it change to 24psi and return quickly to 34psi at tick over. So my understanding is that at tickover the fuel rail should be 22/24psi only going to 34psi at open throttle. The high pressure would result in over fueling i think. So it could be the regulator, blockage in the return pipe or no vacuum or air leak in the tube to the regulator.
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