No it does not seem to hesitate when cold
Yes, this makes it begin to look like the lambda sensor is the cause of the problem.
|
|
|
These 6 cylinder engines suffer with a split/fractured breather hose that can cause erratic function of the lambda sensors.Remove the top plastic engine cover and locate a flexi rubber pipe that runs from #1to #6 cyls along the inlet manifold and is usually attached to the fuel injection rail.Lift it up and have a good look for any damage.hth
|
SQ
Well I have checked and there is a split in this rubber pipe....now all I have to do is get a replacement and see if it makes a difference!
Edited by Pugugly on 09/03/2008 at 12:46
|
|
OK, I've replaced the split section of pipe and the car seems to be a bit smoother....however, I can still sense a slight regular hesitation when at constant speed...any other ideas....my feeling still is that the Lambda sensors are lazy and need replacing
|
>>slight regular hesitation
Yes, again, this is a symptom of slow switching, another pointer towards replacing the sluggish lambda sensor.
|
|
OK...my next step is to replace the lambda sensors....will have to sort this out during the week...thanks for all your help on this topic....will let you know how it works out.
|
Guide here for BMW e39
www.m5board.com/vbulletin/showthread.php?t=59612
Note the torque wrench settings - I don't know if these are true or will apply to your car!
|
I'd want a long, hard, look at the short [and long] term fuel trim figures before spending hundreds of pounds on oxygen sensors. If they sweep at 1Hz @2500 revs and the emission figures are correct, then there's not much wrong with them.
Cyclone breather boxes fail in droves on these.
|
I'd want a long, hard, look at the short [and long] term fuel trim figures before spending hundreds of pounds on oxygen sensors. If they sweep at 1Hz @2500 revs and the emission figures are correct, then there's not much wrong with them.
Since I replaced the split pipe, the car seems to be running better the further I drive it....does it take a while for the ECU to reprogramme itself?
The sensors were not sweeping at 1Hz but at more like 2-3 secs prior to replacing the damaged pipe althgouh the emission figures seem ok and the computer is indicating that the senors were within spec....I will try and recheck the operation of the sensors when I can get my hands on the diagnostic computer again.....will not be for a few days however.
I would rather not replace the sensors if the problem was just down to the spoit pipe.
|
If the long-term fuel trim was well off-centre; then it will take around 20 miles of varied driving to correct it.
The short-term fuel trim will show instantly if there's an O2 sensor fault as it gives a running average of fuel correction in real time. In layman's terms; the percentage difference between the amount of time spent rich and the amount of time spent lean as compared to the "expected" figure. The actual period length is less important than the overall balance.
At what revs were you seeing the 2-3 second sweeps? Can you hear a hissing sound below the front of the inlet manifold?
|
Average fuel consumption has been around the long term figure of about 31mpg and has not really varied.
The 2-3 second sweeps were certainly evident at idle and I think at higher revs...we did a couple of tests reving the engine to aroudn 4000rpm and I seem to remember that the sweep as still around 2-3 secs....certainly our conclusion was that the sensors appeared "lazy"...I will need to put the car back on the computer to be sure and I cannot do this for some days now.
No appreciable hissing noted below the inlet manifold.
|
The long-term fuel trim is a bit different from a consumption figure.
It's the percentage deviation from the centre of the current fuelling block. If it stays at one extreme of that block for long enough, the ECU ratchets up one and sets a fuel-trim code to alert to what it's had to do.
|
|
OK...I see....however, the ECU had not stored any alerts or codes and the computer could not find anything wrong apart from the slow cycling of the lambda sensors. we did not look at the fuelling data in detail as there was nothing obvioulsy wrong with it.
|
I have a simialr problem on my BMW E46 328I. On the diagnostic machine it raised Air flow sensor problem. I was just about to buy a new one for £230. However read this message and I have a hiss under acceleration from idle sounds like its coming from below the front of the inlet manifold.
Do you have any ideas?
SNIPQUOTE
Edited by Dynamic Dave on 27/06/2008 at 19:27
|
Eamon
If you have a hiss from under the front of the inlet manifold, then there is a very good chance that the cyclone breather has split. This will usually flag a long-term fuel trim code like P0171. [Or many similar ones.]
What was the code recorded?
|
I cant actually remember the code but it deffinately said either AIR SENSOR or AIR MASS. I will be putting it back on the diagnostice machine tomorrow. I actually had the cyclone valve replaced last year so shouldnt be that.
When I accelerate/rev from idle between 800-2000 I can hear the engine trying to suck. The car then gurgles a little.
Recently in traffic whilst my wife was driving 50mph-60mph the car started to judder loose power and either the EML or ENGINE light came on. Turning the ignition off and restarting seemed to work. I then drove it in drive and there seemed to be a hesitation when accelerating from low revs. The vehicle is automatic with steptronic so I drive it in sports or manual trying to keep the revs up.
The car doesnt stutter when idling and still easily gets inot 3 figures mph. However there is a slight hesitation constantly when driving. There are know problems with gearchange.
Just want to get it sorted ASAP but dont want to replace parts that dont need changing.
I have read on another website that it could be a vacume leak before the throttle body, it states that this is causing an airleak after the MAF. Have tried to check but cant see anything obvious.
|
|
|
