E36 328is Crazy high fuel consumption

[czerwiec]

Very good read, lots of useful info here. How can you tell if your cat is blocked? How do you check it?

[sidpinup]

OptiManc said:

Well it has been a good number of days since i changed the cam sensor and 2 days later i reset the ECU by disconnecting the battery for a short while.

Verdict, i think the problem has been resolved partly. performance has recovered, now its great from standstill, doesn’t seem or sound laboured and is prompt as it used to be around a year ago. However, fuel consumption has improved also but still fluctuates. My driving style has changed since the issue became apparent, so i rely on the Range on the OBC, and that seems be to more stable than counting down the miles like a stopwatch like it used to. However, it is temporal so i think the problem is only half resolved. I am going to change the o2 sensors too (after pay day) and monitor again.

Like for like driving with the issue and now partially resolved, i would summarise to say we're nearly there.

Thank you to everyone for their contribution, knowledge sharing and support in this thread, your input has been very much appreciated.

I'll update again after changing the o2 sensors.

Great, glad you have made some progress. Also dont forget there are two cam sensors so doing both will make sure you have that area sorted. It was the input cam on mine which is a fiddle to do but I changed out both to be sure. I think I have a spare exhaust sensor if you need one? I know it's an obvious one but have you checked the spark plugs? If not it's worth popping a new set in.

[OptiManc]

sidpinup said:

Great, glad you have made some progress. Also dont forget there are two cam sensors so doing both will make sure you have that area sorted. It was the input cam on mine which is a fiddle to do but I changed out both to be sure. I think I have a spare exhaust sensor if you need one? I know it's an obvious one but have you checked the spark plugs? If not it's worth popping a new set in.

2 cam sensors? Where is the other one positioned? i changed the one to the front of the engine next to the VANOS solenoid.

Thanks for the offer its very kind but i've already bought the O2 sensors.

Plugs have been changed 3 times, once myself then again on Inspection 2 and again on Inspection 2 - desperate times!

[sidpinup]

It's in the same position but on the other side of he head. As you look at the front of the car it's on the left of the engine just by the radiator or is on the 7 series. There is a lead into it so you should be able to spot it. It's likely to be gone also as there is more heat on he exhaust side. It's a different configuration of sensor to the input one you have replaced but easier as the cable plugs in rather than being attached.

[OptiManc]

sidpinup said:

It's in the same position but on the other side of he head. As you look at the front of the car it's on the left of the engine just by the radiator or is on the 7 series. There is a lead into it so you should be able to spot it. It's likely to be gone also as there is more heat on he exhaust side. It's a different configuration of sensor to the input one you have replaced but easier as the cable plugs in rather than being attached.

Cant spot it, i see one going into the radiator and plenty of leads around the engine bay but nothing on the lfft of it that looks like a sensor fitting...can you offer any more clues? We are talking about an M52 straigh 6 right?

[sidpinup]

I just checked and not all have 2 sensors only the later twin vanos version. Sorry for the bum steer.

[OptiManc]

sidpinup said:

I just checked and not all have 2 sensors only the later twin vanos version. Sorry for the bum steer.

Thats OK, checked with mechanic too and single VANOS only has one. Thanks anyway!

[OptiManc]

E30M3SE said:

Are you refering to the crank sensor as per #9..



?

Nice diagram! Yes exactly that, i replaced it over a week ago and its made some improvements to performance and help improved fuel consumption but only yesterday and today o've noticed its gone downhill again, performance and mpg.

[E30M3SE]

..and you've read codes,

Any coming up?

[OptiManc]

E30M3SE said:

..and you've read codes,

Any coming up?

Had codes checked a few times by mechanic on his computer. Only MAF sensor so replaced that but still nothing.

Besides O2, radiator temp, cam position sensor which other engine sensors are there that are involved with fuel, combusion and exhaust? perhaps its worth changing them all?

[kavman0]

Sorry I haven't read the whole thread but I did read this recently. Worth a try maybe.

http://forum.bmw5.co.uk/topic/65604-poor-starting-...

[OptiManc]

kavman0 said:

Sorry I haven't read the whole thread but I did read this recently. Worth a try maybe.

http://forum.bmw5.co.uk/topic/65604-poor-starting-...

Very helpful kavman, thanks. The temp sensor was suggested to me at the start of the thread but the cam sensor carried more momentum so i went for swap on that, will try and get atemp sensor sorted for teh weekend.

[OptiManc]

Can anyone advise on where the inlet air temperature sensor would be located on the M52?

[E30M3SE]

On the underside of the inlet manifold.

Part #14




Which sensor have you replaced to date, the cam or crank?

The sensor in the diagram I posted previously is the crank sensor, the cam sensor is located in the rhs of the head, part #17

Edited by E30M3SE on Friday 11th May 15:18

[OptiManc]

E30M3SE said:

On the underside of the inlet manifold.

Thanks, is it easily accessible or does it need the entire assembly to be taken apart?

[E30M3SE]

Remove the air filter housing (airbox) and you should be able to reach it without taking off the entire inlet manifold.

[OptiManc]

E30M3SE said:

On the underside of the inlet manifold.

Part #14




Which sensor have you replaced to date, the cam or crank?

The sensor in the diagram I posted previously is the crank sensor, the cam sensor is located in the rhs of the head, part #17

Edited by E30M3SE on Friday 11th May 15:18

Great diagrams, thanks. To date I have changed the cam sensor, Part #17 only, is crank work a go too? I am planning on changing the O2 pre and post this weekend weather permitting and now possible the AIT sensor if i can get hold of one before the shops close.

[E30M3SE]

How many miles are on this car?

I just find it somewhat strange that if all these sensors on your car are 'goosed' it does not bring up any fault codes..............

Your way of actually measuring fuel consumption leaves lots of room for errors, have you actually filled the tank to the brim run the car until almost empty, refilled then calculated your mpg over the distance covered?

[OptiManc]

E30M3SE said:

How many miles are on this car?

I just find it somewhat strange that if all these sensors on your car are 'goosed' it does not bring up any fault codes..............

Your way of actually measuring fuel consumption leaves lots of room for errors, have you actually filled the tank to the brim run the car until almost empty, refilled then calculated your mpg over the distance covered?

Exactly! It has passed the MOT with flying colours and I've had the emission tested numerous times.

I have filled it from empty, i mean from being stranded in the middle of a junction to i think 65ish litres or more until it would taje no more. Casual driving with some motorway, to empty again and stranded again at the same junction.

Mostly I keep the Range on the OBD and even when driving like a good boy its still counting down in big jumps, sometimes i've looked at the guage while stationary and the finger is on say 1/4 of tank, as i've moved off its clearly past the 1/4 mark! Since changing the cam sensor it began to improve but last night and now today its gone back to exactly how it was, although performance hasnt been affected as dramatically.

[E30M3SE]

So how many miles did you get on the '65ish' litres?