My faultless car of 4 years has developed a fault!
Discussion
My 1996 (P) BMW 323i Coupe that has been free from any problems in the 4 years I've owned it has this morning developed a fault. At any speed and in any gear, when the accelerator is pressed more than half to two thirds of the way down, the usual surge in power is not there. The car still accelerates, but it feels like only half the power is left and backing off slightly actualy restores some of the lost power. While this is happening a slight grumbling noise is coming from the engine, disappearing again when I back off a bit.
There is no check engine light coming on and the engine looks fine, oil level correct, clean and normal smelling oil, no traces of anything unusual in the coolant, sparkplugs look in top condition, no cracks or damage to the coil packs, no smoke from the exhaust, engine idles beautifully and below half throttle performs as usual. Nothing at all to indicate anything out of the ordinary.
I've booked it in for a service at the local specialist, but they can't see me till friday and as I don't have any car to replace it for the daily drive (I'm not using the MG!) I'm at a loss as to what to do. So does anyone here have a clue what it might be or what I could check? Any help at all would be usefull.
The only things I can think of that might be at fault, but that I can't check without diagnostic equipement are the lambda sensor, the knock sensor and worst case scenario, the Vanos.
There is no check engine light coming on and the engine looks fine, oil level correct, clean and normal smelling oil, no traces of anything unusual in the coolant, sparkplugs look in top condition, no cracks or damage to the coil packs, no smoke from the exhaust, engine idles beautifully and below half throttle performs as usual. Nothing at all to indicate anything out of the ordinary.
I've booked it in for a service at the local specialist, but they can't see me till friday and as I don't have any car to replace it for the daily drive (I'm not using the MG!) I'm at a loss as to what to do. So does anyone here have a clue what it might be or what I could check? Any help at all would be usefull.
The only things I can think of that might be at fault, but that I can't check without diagnostic equipement are the lambda sensor, the knock sensor and worst case scenario, the Vanos.
^^
I Wouldn't rule it out but an air leak would surely only be a problem at less than 60% WOT? Over that the MAF is redundant and therefore there is nothing metering the airflow (?)
I'd be tempted insted to go down the fuel pump route as it sounds to me more like a fuel starvation issue - which might tigh in with the 'grumbling' noise you have.
I Wouldn't rule it out but an air leak would surely only be a problem at less than 60% WOT? Over that the MAF is redundant and therefore there is nothing metering the airflow (?)
I'd be tempted insted to go down the fuel pump route as it sounds to me more like a fuel starvation issue - which might tigh in with the 'grumbling' noise you have.
Edited by ASBO on Tuesday 27th May 16:24
Hmm, fuel starvation is something I hadn't thought about. I'll look into that in the morning.
I tested the throttle position sensor through it's full range and that seems to be working fine, so that's ruled out. I also did a compression test and all cylinders are gettig a healthy 14 bar on the meter with no noticable difference between them. (Bentley manual states 10-11 bar as the minimum).
So I'm thinking it's either the knock sensor, lambda sensor, Vanos or fuel flow that's at fault. All else (as far as I can think of) checks out as fine and in top condition.
I tested the throttle position sensor through it's full range and that seems to be working fine, so that's ruled out. I also did a compression test and all cylinders are gettig a healthy 14 bar on the meter with no noticable difference between them. (Bentley manual states 10-11 bar as the minimum).
So I'm thinking it's either the knock sensor, lambda sensor, Vanos or fuel flow that's at fault. All else (as far as I can think of) checks out as fine and in top condition.
I've had a similar problem, but in a e39 530 Auto sport.
Putmy foot on the pedal and the car goes ok, but if i was to push more than halfway there would be a loss of power.
This was due to the Co2 and o2 sensor not working correctly. As soon as these were replaced the car was fine.
It might not be the same for your 328, but it's an idea.
Putmy foot on the pedal and the car goes ok, but if i was to push more than halfway there would be a loss of power.
This was due to the Co2 and o2 sensor not working correctly. As soon as these were replaced the car was fine.
It might not be the same for your 328, but it's an idea.
Sounds eerily like what happened to my E36 318ti when the cat failed. Loss of power when you boot it, restored by very gentle use of throttle.
Stop driving it right now - the reason being that you could end up with bits of the ceramic interior of the cat rattling around your engine, and that would be very bad.
Get it into the hands of the spannermen ASAP.
The bad news is that this is an expensive part - probably about £300 by the time you've added VAT and labour.
Caveat: this was all a couple of years ago for me, so prices may have gone up or down in the interim.
Stop driving it right now - the reason being that you could end up with bits of the ceramic interior of the cat rattling around your engine, and that would be very bad.
Get it into the hands of the spannermen ASAP.
The bad news is that this is an expensive part - probably about £300 by the time you've added VAT and labour.
Caveat: this was all a couple of years ago for me, so prices may have gone up or down in the interim.
Edited by CommanderJameson on Thursday 29th May 07:56
Shropshiremike said:
Is it idling OK when you stop quickly at a junction?
Does it start OK?
Yeah, everything runs fine, starts and idles as normal. Just a loss of power as described and nothing else. I'm taking it to the specialist tomorrow, so I'll see what they say. I'm willing to bet it's the lambda sensor though...Does it start OK?
Ravell said:
Shropshiremike said:
Is it idling OK when you stop quickly at a junction?
Does it start OK?
Yeah, everything runs fine, starts and idles as normal. Just a loss of power as described and nothing else. I'm taking it to the specialist tomorrow, so I'll see what they say. I'm willing to bet it's the lambda sensor though...Does it start OK?
Right, got a phone call yesterday and it turns out the catalist has actualy melted, forming an obstruction. At low revs and load the exhaust gas can get past it relatively normaly, but at high loads it's not flowwing right obviously.
They've quited me 500 pounds for an original BMW cat or about 200 for a decent reproduction, but I'm guessing that the engine must be running rich for the cat to melt, which would mean the O2 sensor is needing replacement too. Which would be weird as the sparkplugs didn't seem to indicate a rich mixture or any other abnormality when I took them out to do the compression test.
I'm tempted rather then get a new cat, to buy a full used exhaust system from a breakers or something from an M3, including the tuned length manifold. Might cost about the same be sound better and free up the breathing. Not sure if I'm right about the cost or weather an S50 system fits straight onto an M52 block though.
At least it wasn't a Vanos problem!
They've quited me 500 pounds for an original BMW cat or about 200 for a decent reproduction, but I'm guessing that the engine must be running rich for the cat to melt, which would mean the O2 sensor is needing replacement too. Which would be weird as the sparkplugs didn't seem to indicate a rich mixture or any other abnormality when I took them out to do the compression test.
I'm tempted rather then get a new cat, to buy a full used exhaust system from a breakers or something from an M3, including the tuned length manifold. Might cost about the same be sound better and free up the breathing. Not sure if I'm right about the cost or weather an S50 system fits straight onto an M52 block though.
At least it wasn't a Vanos problem!
Right, got the car back this morning and found a cheap 328i exhaust system in good condition from a BMW breakers. Just need to undo the bolts that hold the whole lot onto the manifold.
Anyone know any tricks to getting these b
ds off? Their very coroded and although a 13mm socket still fits nicely once the scale is removed, I'm scared to death of stripping them and finding myself up st creak without a paddle. I've already soaked the bolts on the whole system with WD40 but I doubt that will help much.
Anyone know any tricks to getting these b
ds off? Their very coroded and although a 13mm socket still fits nicely once the scale is removed, I'm scared to death of stripping them and finding myself up st creak without a paddle. I've already soaked the bolts on the whole system with WD40 but I doubt that will help much.Conclusion to the whole escapade:
I've finally fitted the 328i system I found after a LOT of hard work! Fitted just fine, needing no alterations or other parts appart from a slightly bigger cutout in the lower bumper pannel. Weighs a ton, but so does the old system, there really isn't any difference.
The engine does sound so much better with the double pipes. Maybe a bit quieter than I would have liked, but it sounds much smoother and more basey than with the single pipe system. Maybe I'm imagining it, but it feels like it's pulling better through the gears too.
Some pics for anyone interrested in the differences:
I've finally fitted the 328i system I found after a LOT of hard work! Fitted just fine, needing no alterations or other parts appart from a slightly bigger cutout in the lower bumper pannel. Weighs a ton, but so does the old system, there really isn't any difference.
The engine does sound so much better with the double pipes. Maybe a bit quieter than I would have liked, but it sounds much smoother and more basey than with the single pipe system. Maybe I'm imagining it, but it feels like it's pulling better through the gears too.
Some pics for anyone interrested in the differences:
CommanderJameson said:
Stop driving it right now - the reason being that you could end up with bits of the ceramic interior of the cat rattling around your engine, and that would be very bad.
How does it get into the engine? Is the cat upstream of the turbo?Edited by CommanderJameson on Thursday 29th May 07:56
crackedfinger said:
CommanderJameson said:
Stop driving it right now - the reason being that you could end up with bits of the ceramic interior of the cat rattling around your engine, and that would be very bad.
How does it get into the engine? Is the cat upstream of the turbo?This may, of course, just be grist to the "allow CJ to touch nothing under the bonnet" mill...
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