E36 Severe Power Loss Under Acceleration - No stalling, No EML, No Rough idle

**CaptainsLog** · 01-27-2019, 11:27 AM

Hi guys,

I've recently acquired a 1997 323i SE Auto with the 2.5 M52 in it. Around a month ago I sealed the deal, the engine is mint and the car in general has been well looked after. It's run 140k plus miles but pulls like a dream, that is until yesterday morning.

Given, since I have had it I have drove it pretty hard on a daily basis I like to make the most of those 2.5 litres where my wallet permits. A few days ago a rattling started from what appears to come from the centre box on the exhaust. It was concerning me, but I thought a bracket may be loose or something. Anyway, this has gradually gotten worse and I am unsure if this is related or not, but I was driving it yesterday, I had stopped at a roundabout and was about to take off to turn it and all of a sudden there was tremendous power loss on acceleration. Ironically, there was an AA van behind me.

I quickly rerouted and made my way to a local garage I know who kindly plugged me up to their Snap-On code reader and it popped a code up for camshaft position sensor. Not sure if this was an old code or not though, there was no EML on whatsoever, no rough idle, no stalling, no lumpy running, no failed starts etc. and if I accelerate slowly I can build up speed quite easily. But if I put my foot to the floor where I'd usually find my power, it groans awfully like there isn't enough air coming through or like there is a blockage in the exhaust or something.

I did wonder if the cat had broken apart and was blocking the exhaust? Any tips or has anybody had similar situations? The engine runs absolutely spot on when idle so find it hard to believe it's a sensor.

**Eric93se** · 01-27-2019, 12:29 PM

Well they are both possible. When you replace the cam sensor it has to be OEM. If the cat is clogged you should be able to use a vacuum gauge to help diagnose it

**CaptainsLog** · 01-27-2019, 12:41 PM

Originally Posted by Eric93se

Well they are both possible. When you replace the cam sensor it has to be OEM. If the cat is clogged you should be able to use a vacuum gauge to help diagnose it

Why does it have to be OEM? Does it matter? OEM will be hella expensive, no?

**marvinstockman** · 01-27-2019, 02:01 PM

Just buy something from a reputable manufacturer and supplier.

**Eric93se** · 01-27-2019, 03:38 PM

Siemens or VDO

If you can't find it cheap in your country, then these guys will ship for a decent price.
https://www.ebay.com/itm/For-BMW-323...O/351443945643

**CaptainsLog** · 01-28-2019, 06:12 AM

Bought one from my local EK brakes, Valeo or something. Guys, I don't think this is the issue though. I am almost certain the exhaust is blocked. How can I diagnose this without a pressure gauge? The accel. is fine if I lightly hold down the pedal and the car has no issues idling, starting, pulling away or any other kind. It's when I put my foot to the floor it groans so loud and sounds like pressure is building up in the exhaust. The exhaust rattles from the centre, I don't know where the cat(s) actually is on this exhaust. My mechanic friend suggested to straight pipe the car and find out if that helps.

Please check out this video, does it sound like the camshaft sensor needs replacing? Vacuum leak?

**Eric93se** · 01-28-2019, 01:22 PM

Watch YouTube vids, blocked exhaust pressure gauge

**Audi200tq** · 01-29-2019, 01:12 AM

Classic hesitation/bogging/loss of power. There's a huge thread on this. Essentially you have to start replacing things until it's fixed. The codes aren't always accurate, but start with the CPS. If that doesn't fix it, and the cat checks out, I recommend new spark plugs and new coils, in that order. If it's still not working, start changing out all the sensors: MAF, O2, TPS, temp, etc etc. Buy new OEM or from a reputable brand name. Start with the cheapest and easiest-to-access sensor, and go from there. Let me know how it goes.

**ed323i** · 01-29-2019, 08:14 AM

Tip: Find a complete exhaust from a 328i.. The 323i is fitted from factory with the single pipe 320i exhaust.. It's quite big diameter so it doesn't suffer too much, but with the dual-pipe 328i exhaust it will sound better, and, especially when you also chip tune the DME, the power will definitely increase.. I'm very happy with the combined upgrade (exhaust+dme tune). Really transformed the car, and it's a plug&play upgrade (identical fitting to 323i exhaust).

**CaptainsLog** · 01-29-2019, 11:42 AM

Originally Posted by ed323i

Tip: Find a complete exhaust from a 328i.. The 323i is fitted from factory with the single pipe 320i exhaust.. It's quite big diameter so it doesn't suffer too much, but with the dual-pipe 328i exhaust it will sound better, and, especially when you also chip tune the DME, the power will definitely increase.. I'm very happy with the combined upgrade (exhaust+dme tune). Really transformed the car, and it's a plug&play upgrade (identical fitting to 323i exhaust).

Thanks for the tip, I'll go down that route then if the sensor doesn't help.

Originally Posted by Audi200tq

Classic hesitation/bogging/loss of power. There's a huge thread on this. Essentially you have to start replacing things until it's fixed. The codes aren't always accurate, but start with the CPS. If that doesn't fix it, and the cat checks out, I recommend new spark plugs and new coils, in that order. If it's still not working, start changing out all the sensors: MAF, O2, TPS, temp, etc etc. Buy new OEM or from a reputable brand name. Start with the cheapest and easiest-to-access sensor, and go from there. Let me know how it goes.

Thanks, yeah I don't know what happened. It's gotten worse since, to the point where I can no longer drive it safely out of the cul-de-sack I live in without having to spin it back round. I'll upgrade the sensor and update you from there. It was supposed to arrive today, but I guess the delivery was delayed by snow as it is neatly 5pm now and not here

**Nanniepoo** · 01-29-2019, 01:14 PM

This might sound like an odd suggestion, but check your guibo. It's a flex disc between the trans and driveshaft. It definitely will make a lot of noise while it's failing, under hard acceleration at first, and as it worsens, normal acceleration. Can also feel like you're low on power and the car is struggling. And explains why engine sounds healthy at idle.

**ed323i** · 01-29-2019, 05:07 PM

Rereading your first post, in which you note that the power reduction happened all of a sudden..
I would think that an exhaust/cat getting clogged, won't happen in an instant. You'd expect it to be a gradual process?

So, some sensor going bad seems more like it..

Another tip: Because the MS41 DME is quite advanced, you can disconnect quite some sensors to diagnose them.
For example: Engine should run fine without the camshaft position sensor connected, and also with crankshaft position sensor disconnected, as long as you don't disconnect both at the same time of course. MAF sensor you can also safely disconnect. Should run very well without it, a bit less power, but should run fluently. That way, if, after disconnecting a sensor, you regain your power, you know where to look. Same for oxygen sensors. Coolant sensor too (but will cope better with engine already warmed up). Intake air temperature sensor can be disconnected too.

That way you can diagnose a lot of things without having to throw a lot of money at it.

Good luck!

**M3AN** · 01-30-2019, 03:18 AM

And yet nobody has asked:

What do your revs do when you're accelerating hard? Do they climb as expected (but without the resulting power to the wheels) or do they bog down?

That's an essential piece of diagnostic information that seems to be missing... especially since it's an auto.

Certainly don't start replacing parts... :-/

If you really think it's the exhaust then remove it and take the car for a (short) run, you'll soon isolate the exhaust if it's the cause.

**CaptainsLog** · 01-30-2019, 06:50 AM

Originally Posted by Nanniepoo

This might sound like an odd suggestion, but check your guibo. It's a flex disc between the trans and driveshaft. It definitely will make a lot of noise while it's failing, under hard acceleration at first, and as it worsens, normal acceleration. Can also feel like you're low on power and the car is struggling. And explains why engine sounds healthy at idle.

Hmm, ok thanks I will take a look at that.

Originally Posted by ed323i

Rereading your first post, in which you note that the power reduction happened all of a sudden..
I would think that an exhaust/cat getting clogged, won't happen in an instant. You'd expect it to be a gradual process?

So, some sensor going bad seems more like it..

Another tip: Because the MS41 DME is quite advanced, you can disconnect quite some sensors to diagnose them.
For example: Engine should run fine without the camshaft position sensor connected, and also with crankshaft position sensor disconnected, as long as you don't disconnect both at the same time of course. MAF sensor you can also safely disconnect. Should run very well without it, a bit less power, but should run fluently. That way, if, after disconnecting a sensor, you regain your power, you know where to look. Same for oxygen sensors. Coolant sensor too (but will cope better with engine already warmed up). Intake air temperature sensor can be disconnected too.

That way you can diagnose a lot of things without having to throw a lot of money at it.

Good luck!

Thanks for this info, I wasn't sure if I could start disconnecting things and running the car round the block with them off. I will take the camshaft sensor on the intake off this morning then, I've ordered the part but it hasn't arrived, but if it runs fine without can I assume that is what's causing the issue? Same with the o2 sensors. I've got no ramps so gonna be sketchy getting underneath it.

------

The car revs were fine, I could drive it fine even without power if I gently accelerated. But I noticed on a cold start yesterday I tried to take my girlfriend to work as she was late, the revs did not increase past 2k and there was no power whatsoever. I got to the end of my cul-de-sack road and carefully turned it back round and parked it up lol.

**CaptainsLog** · 01-30-2019, 09:59 AM

Ok, update on the car. This morning I turned it on, started it up and it was quite rough idling, I gave it some revs and the revs felt elastic, they'd go up and come back down quite faster, faster than usual. Gave it some more RPM and it started to cut out when the RPM came back down. So I turned it off. As for removing the sensor, I *disconnected* the camshaft position sensor at the intake and the car wouldn't start at all. Cranked fine, but wouldn't even try to fire. As for replacing the sensor, can't get the vanos solenoid off so wanted to come here and see if you guys, specifically @ed323i had any insight on what to try next?

**ed323i** · 01-30-2019, 12:16 PM

Can you try the inverse? So, let's assume the camshaft sensor is fine, and that crankshaft sensor is bad. So, can you disconnect camshaft sensor, and connect camshaft sensor, and see if it wants to start (cranking time might be little longer before DME understands what's happening)..

**CaptainsLog** · 01-30-2019, 02:55 PM

Originally Posted by ed323i

Can you try the inverse? So, let's assume the camshaft sensor is fine, and that crankshaft sensor is bad. So, can you disconnect camshaft sensor, and connect camshaft sensor, and see if it wants to start (cranking time might be little longer before DME understands what's happening)..

Yes, ok I will try that tomorrow. Is the crankshaft sensor connected in the same place as the camshaft sensor, just behind it? I think the actual sensor is at the front on this engine, underneath the radiator etc. bit of a ballache trying to get my hand through under the manifold. I removed the airbox earlier, gave me a little bit more room but the airbox was a nightmare to get back in.

**Nanniepoo** · 01-30-2019, 03:59 PM

Well I think you can safely disregard my guibo recommendation at this point

**CaptainsLog** · 01-30-2019, 04:03 PM

Originally Posted by Nanniepoo

Well I think you can safely disregard my guibo recommendation at this point

How come? Oddly enough, the rattling wasn't present today. Not sure if it's just because it hadn't had a chance in the 30 seconds the car was on or not but odd.

**Nanniepoo** · 01-30-2019, 04:07 PM

Originally Posted by CaptainsLog

How come? Oddly enough, the rattling wasn't present today. Not sure if it's just because it hadn't had a chance in the 30 seconds the car was on or not but odd.

Your latest posts definitely point to an engine/sensor problem

**CaptainsLog** · 01-30-2019, 05:35 PM

Originally Posted by Nanniepoo

Your latest posts definitely point to an engine/sensor problem

Okay, do you have any insight personally into what it sounds like it could be in particular?

**ed323i** · 01-30-2019, 05:48 PM

With my European M52, it's very easy to find the crankshaft position sensor, as it's on the front (radiator side) of the engine.. But with the US M52, I think it's on the firewall side and a bit more difficult to get to. Perhaps someone else with experience in that department can give some advice.

Update: Already found it. Not too much work:

**CaptainsLog** · 01-30-2019, 06:00 PM

Originally Posted by ed323i

With my European M52, it's very easy to find the crankshaft position sensor, as it's on the front (radiator side) of the engine.. But with the US M52, I think it's on the firewall side and a bit more difficult to get to. Perhaps someone else with experience in that department can give some advice.

Update: Already found it. Not too much work:

Oh, it's a European M52, so it's at the front then? Where's the connector situated?

**ed323i** · 01-30-2019, 07:32 PM

I haven't replaced it yet personally, but you can see the toothed wheel mounted on the front of the engine, and if you look around you'll see the sensor. Then follow the leads until you find a connector.

Update: The connector is under the intake manifold. If you have (or know someone with) small hands, you might get to it, but otherwise you might have to remove the oil filter, so you get a bit more play..

Also have a look at: https://www.pelicanparts.com/bmw/tec...aft-Sensor.htm

**Thomas525** · 01-30-2019, 09:18 PM

Have not read this whole thread to sorry if this has been suggested. It could be your fuel pump or a damaged fuel pressure regulator. Clogged fuel filter even. Possibly bad fuel pump relay - easily tested. Basically, fuel starvation. If after you do the sensor disconnect test you are no closer to isolating the problem, I would look at the fuel system setup before looking at the exhaust.

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Pull out the fuel pump fuse and see if it looks melted or weird even if the fuse wire itself within it is intact.