Discussion
My 1990 350i idles at around 1000 rpm, (when I take it lower it is a little unstable). During the day things are pretty good, the fan cuts in my idle goes down to 900 rpm and I remain a happy wedge driver.
However at night with lights up I have a problem, idle goes down to 500 rpm when the fan cuts in and dies.
For some reason this happens more frequently when I am waiting to turn right and have the steering hard over !
Why doesn't the ECU compensate for the extra load on the altenator ? Does anyone have a similar problem ?
I can over come it with a 1200 rpm idle, but what a waste !!
Please any advise, thanks Keith
However at night with lights up I have a problem, idle goes down to 500 rpm when the fan cuts in and dies.
For some reason this happens more frequently when I am waiting to turn right and have the steering hard over !
Why doesn't the ECU compensate for the extra load on the altenator ? Does anyone have a similar problem ?
I can over come it with a 1200 rpm idle, but what a waste !!
Please any advise, thanks Keith
Several things at work here: perhaps a dying battery for a start. After that, could be lack of charge from the alternator, bad earth, decayed wiring etc.
Then you have the full-steering-lock syndrome; it's fairly common, although my car usually copes.
The ECU can't compensate because nobody told it it has to! Although it gets a trigger signal from the ignition system and therefore theoretically knows that the engine is slowing down, it doesn't actually have any means of knowing what the idle speed 'should' be.
Modern systems are closed-loop and the ECU controls fuel and ignition, so they're a lot more stable these days.
Not a lot of help, I know.
Ian
Then you have the full-steering-lock syndrome; it's fairly common, although my car usually copes.
The ECU can't compensate because nobody told it it has to! Although it gets a trigger signal from the ignition system and therefore theoretically knows that the engine is slowing down, it doesn't actually have any means of knowing what the idle speed 'should' be.
Modern systems are closed-loop and the ECU controls fuel and ignition, so they're a lot more stable these days.
Not a lot of help, I know.
Ian
Bloody hell. Forgot to say (owing to the fact that you can't see the post you're replying to!!) that 1000RPM is way too high anyway for a V8. Should be more like 800+/-50 RPM. Mine's 800 but I can get it down to about 600 with a fair degree of stability! Just that the oil pressure is then a bit low.
Sounds like you need a general tune-up, you may then find that things improve.
Ian
Sounds like you need a general tune-up, you may then find that things improve.
Ian
1,000 is not too high for all Wedges. My (very tuned) 350i used to suffer the fan cut in and die syndrome when it idled at 900. Now properly set up at 1,000 by Tower View -- excellent by the way thanks to Steve for the recommendation -- it's fine (emmissions OK, no noticable change in fuel consumption). The ECU does not appear to cope with changes in electrical load as well as mainstream cars.
My Wedge used to stall if I yanked the power steering a bit quickly. Peninsula traced it to a minute hole in the air intake tubing between the airflow meter and the plenum chamber. They said they couldn't see the hole, but it was there. The tube would be a (relatively) cheap and easy thing to try changing.
By the way - my Wedge is idling at 1400 revs at the moment and wont idle reliably below that. It's just that with my engine setup the idle is extremely lumpy; the extra revs are needed! It's all to do with the wierd setup in my engine, a suspected hot cam and standard head combination. My revs also drop when an electrical load is turned on, but since the air hole was fixed I haven't been in danger of stalling the engine.
By the way - my Wedge is idling at 1400 revs at the moment and wont idle reliably below that. It's just that with my engine setup the idle is extremely lumpy; the extra revs are needed! It's all to do with the wierd setup in my engine, a suspected hot cam and standard head combination. My revs also drop when an electrical load is turned on, but since the air hole was fixed I haven't been in danger of stalling the engine.
Hi Guys, Thanks for the imput. A few other condiderations for the pot, I can detect no air leaks, Co is 5.5% and I am running 4 degrees advance (any more and I pink badly). I have cleaned as many electrical contacts as possibly and have changed the plugs and leads. 1200 RPM at idle is such a waste, does anyone know what a Rover Vitesse idle should be ?
My wedge seems to run pretty well other than this glitch. I guess a rolling road tune would help ?
Keith
My wedge seems to run pretty well other than this glitch. I guess a rolling road tune would help ?
Keith
Keith 5.5% is rich, reduce to 3.5%max, but watch the hydrocarbons,go too low on Co and hydrocarbons go sky high. try NGK B7ECS if you haven't already, how are you checking for air leaks ? the best way is to spray cleaning fluid and see if the engine speed changes.
Tim
>> Edited by 2 Sheds on Friday 23 August 18:01
>> Edited by 2 Sheds on Friday 23 August 18:04
Tim
>> Edited by 2 Sheds on Friday 23 August 18:01
>> Edited by 2 Sheds on Friday 23 August 18:04
Sounds like you've answered your own question there: once you get the CO down it'll probably stand more advance and run smoother (and slower) anyway.
I run with the advance off the scale, I guess about 14 degrees or so, and last time I fiddled (with fuel pressure!) I got the CO down to 0.6%. Still not happy with it though; like yourself I can feel a rolling road tune coming on... ;-)
Ian
I run with the advance off the scale, I guess about 14 degrees or so, and last time I fiddled (with fuel pressure!) I got the CO down to 0.6%. Still not happy with it though; like yourself I can feel a rolling road tune coming on... ;-)
Ian
Got to say it does sound like an air leak might be the culprit - I'd agree with 2 Sheds on diagnosis. I dont really think theres anything wrong with 1000RPM idle - mine is set at 1200, similar to NACNUD - sporty cam etc and it just saves a lot of hastle when the electrics are loaded up.
Gentlemen, A further update. I have taken 2 Sheds advice and lowered the Co to 3.5 and rechecked the possible air leak situation (still can't find any !)
I now have a fairly steadly idle of 1050 which drops to 950 when the fan cuts in. Do you think advancing the ignition would be benefitial (currently 4 degrees)? Also does anyone run the full 8 degrees with unleaded ?
Thanks for the help.
Keith
I now have a fairly steadly idle of 1050 which drops to 950 when the fan cuts in. Do you think advancing the ignition would be benefitial (currently 4 degrees)? Also does anyone run the full 8 degrees with unleaded ?
Thanks for the help.
Keith
Run a standard 350i, 5,0% CO with 8 degrees.
Use only 98 Ron unleaded without any problems for 10.000 km (had the TVR only for 8 months).
Engine now on 160.000km (no revisions).
Only pinks if the fuel tanks are nearly empty under full "long time" acceleration (0 - 100 miles/hour) and high revs (over 5000 rpm). I change up and the pinking is gone.
I assume it probably takes too long for the pump to recycle the returned fuel - because it happens only when I'm below 10 - 15 liters (for UK less than 3-4 gallons?)remaining.
Rob, Belgium.
Use only 98 Ron unleaded without any problems for 10.000 km (had the TVR only for 8 months).
Engine now on 160.000km (no revisions).
Only pinks if the fuel tanks are nearly empty under full "long time" acceleration (0 - 100 miles/hour) and high revs (over 5000 rpm). I change up and the pinking is gone.
I assume it probably takes too long for the pump to recycle the returned fuel - because it happens only when I'm below 10 - 15 liters (for UK less than 3-4 gallons?)remaining.
Rob, Belgium.
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