hi reving on idle ?????

[fordy]

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[trefor]

I'd clean the stepper motor before doing anything else - seems to be the cause of a lot of idling problems. T/. Edited by Trefor on Monday 18th June 21:22

[xain]

I think that's actually good proof that it's the idle stepper. When the revs drop, the stepper should intercept it and lower it to idle gently. But as you say it's dropping suddenly then rising, indicating that the stepper is sticking, and not able to reach the correct point fast.

[xain]

Not so. I don't think that the stepper will be "high" up it's range when you're driving along, as it isn't required to do any correction. It will probably be closed. Then when the revs start to drop it must open up to hold the idle. If it does it too slowly (it's sticky) then it may have to try to *really* open it as the ECU thinks it's having not enough effect. In short it just gets bad at finding then holding a given idle. The motor itself is the plastic bit at right on the back of the plenum. Never investigated it more than that myself, but I hear it's dead easy.

[GreenV8S]

Road speed sensor will keep the idle up around 1500 rpm while the car is moving. But a dirty stepper motor is the first suspect for all idle related problems. Cleaning it is dead easy and described in Steve Heath's Griff/Chimaera 'bible'. Cheers, Peter Humphries (and a green V8S)

quote: According to the service ive just had done a Fernies - that has been done - although if it dropped straight to 1500 from say 4000, then i could believe its the stepper motor - but it doesnt it drops to 1000 (true idle) then rises to 1500 - its seems to me its more like a sensor playing up giving duff info to the ECU - but apart from temp i dont know any sensor that tells the engine it needs to rev that high on idle - any ideas ??? cheers Chris

[ozzie]

Where is the road speed sensor, what is its design and how do you access it/ check it cos my 97' 4.5 is still burning very rich and this is the last thing i have to check before I go insane!

[ozzie]

if you find out how to remove the lambda sensors....please post it here as I have the same problem and hope to **** it is the sensors!

[apache]

just had a lamda sensor go in mine, symptoms were:- coughed and died, fired up ok on the starter but would die straight after. As for removing it just unplug it and unscrew it. I get the impression though that if one goes then the motor wont run at all

[GreenV8S]

quote:I get the impression though that if one goes then the motor wont run at all

I've been through half a dozen lambda sensors, a duff sensor will often put the engine into 'limp' mode but has never stopped it running. Cheers, Petrer Humphries (and a green V8S)

[apache]

Peter, picked the car up today, interestingly half a mile down the road it started hickupping badly so I took it back and they ran a diagnostics on it found nothing, the stepper was then checked and found to be reading all over the place. Once the stepper was changed the problem seemed to go away, I was charged £174 for the new sensor and labour. If these do go where can I buy them myself. Ps i saw the emmissions readout and it seems to confirm the duff lambda. I was thinking that it would be bloody useful if Ted could run a cross reference on engine faults for us to pool our experience (which must be considerable)

[xain]

...plus, how *can* you unplug the lambda sensor? It looks like the wires are moulded into the sensor, and they get in the way of a socket spanner. It's recessed too deep for me to get a ring spanner onto it. Anyone managed to get these out?

[steveab]

Apache, Thats curious, my Chim 450 went in for the stepper motor to be cleaned. Now its idle is fine (even on short journeys) but when you start it up the revs shoot up to about 2.5K and vary between .8 and 1.5 ish for about 10 - 20 secs after starting. After that its fine and settles down to about 1K. Is that similar to what you get? - Any ideas? Also, this is probably a daft question but are you supposed to start the engine with a little gas or just leave the throttle alone. I only ask as the 'norm' for EFI cars is no throttle. I've not be told either way!! also I've tried both ways and they don't make a difference. Besides, can't do much at the momment since Webbs are rebuilding my arse! Steve

[GasBlaster]

Went in for the stepper motor to be cleaned? This takes approximately 45 seconds to do and is a lot easier than getting the roof into the boot. I hope you weren't charged too much. Full instructions are given in Steve Heath's book.

[apache]

steveab, idle never was a prob but since I bought the car every once in a blue moon the thing would hiccup and run rough, sometimes with quite alarming results, ie the other half being spun whilst on her way to work in Cambridge, (she is insured) Edited by apache on Friday 13th July 11:15