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E46 325i lacking power :(

1.7K views 9 replies 5 participants last post by  Spindle  
#1 ·
I have just ended up owning my friends E46 325i auto. The car is in real good condition apart from the one issue that he has been trying to fix with me helping him.

To start with it had slow starting issues but always fired up. I spent a lot of time chasing down every air leak it had which seemed to be the majority of normal ones- we fitted a new air intake, new vacuum lines, new genuine BMW inlet manifold gaskets, new PCV, I had the injectors tested and cleaned (1 and 3 were a bit bad but all six are now perfect). It has also had fitted by him - fuel pump, air flow meter, intake vanos solenoid and possibly a few other bits that I cant think of right now. Also had a new starter motor as that decided to give up during all this issue chasing.

After all of this the car now runs but still has the slow start as well as the much more annoying severe lack of power. It rev's freely, during driving if you put your foot down it revs right up to 6k but the speed doesn't follow... I reckon a 1.0 something or other is faster than this 325 at the moment. It feels like it has a punch to start but then after a few meters is just flat.

So I am currently thinking that maybe the cats are blocked? Or the fuel pump he bought is a bit lacking in quality and therefor pressure? I do need to run it with the air flow meter unplugged to see if that makes a difference.

Currently it has no fault codes. It was throwing up E3 and E4 fuel trim above permissible range (for bank 1 and 2) although these have not been seen for a long time now.

Any ideas guys and girls? I'm open to suggestions on what to look at as its now a case of getting it running or breaking it to sell which I'd rather not do.

Cheers.
 
#4 ·
Thanks for your replies.

I was wondering about the torque converter but everything I have looked up says a faulty one results in a juddering movement, this is smooth as you like just very lacking. I have never had an auto and it does remind me of a slipping clutch in a manual so have been wondering if its gearbox related although that would not explain the original e3 / e4 fault codes and the slow starting issue it has would it?

I literally got the car yesterday so no, I've never had it dynoed. I don't think it would help at this point as it struggles to put power down on the road so it's not going to do much on a dyno other than tell me its lacking power and waste my time and money. I will get it on the dyno once its fixed though as I have a friend with one.

The slow start issue makes me think it is not gearbox related but as I am new to autos maybe I'm wrong? It turns over no problem but does not fire up until a few attempts of cranking the engine.
 
#6 ·
The point in taking it to be dyno'd wouldn't be to tell you that it's lacking power, but to study the running values which would hopefully tell you WHY its lacking power.
You get a good look at the torque/power curve, check out the AFRs etc. With the car hooked up to a computer you can observe every running parameter accross a variety of load and RPM condition which is exactly what you want in this case.
Or just take it to a BMW specialist and ask them to do a diagnostic on the car out on the road.
You say "waste of money" but how much has been spent on throwing new parts at the car and still not fixed the issue? I would bet 99% that the problem is electronic not mechanical so clearly more thorough diagnostic work is required before undertaking any further work on the car. Around ÂŁ40 is not a lot of money really.
 
#7 ·
The point in taking it to be dyno'd wouldn't be to tell you that it's lacking power, but to study the running values which would hopefully tell you WHY its lacking power.
You get a good look at the torque/power curve, check out the AFRs etc. With the car hooked up to a computer you can observe every running parameter accross a variety of load and RPM condition which is exactly what you want in this case.
Or just take it to a BMW specialist and ask them to do a diagnostic on the car out on the road.
You say "waste of money" but how much has been spent on throwing new parts at the car and still not fixed the issue? I would bet 99% that the problem is electronic not mechanical so clearly more thorough diagnostic work is required before undertaking any further work on the car. Around ÂŁ40 is not a lot of money really.
So far I've spent no money on the car, the previous owner has. I'm merely collecting ideas of what could be causing it as like you I think it is going to end up being something electric not mechanical. I'll let you all know how I get on as and when I get time to investigate it and if it ends up on the dyno to see whats going on.

Thanks for your advice and help .
 
#9 ·
No fault codes, revs all the way to 6k but slow. Most of the usual problems would show up a fault code.
I'd be looking at the transmission to be honest. Have you done a fluid change? Might be a good start?
I'd get it on a dyno or a decent specialist to get a better idea.
Last time I had an M54 that was slow it turned out to be a failed cam position sensor but that threw a code. I knew something was up when my 330i got out dragged by a Fiesta ST (2.0 N/A one, not Turbo)
 
#10 ·
Ok just so this is not one of those forum threads that someone in the future finds with the same issue and the answer was never posted......

Problem solved! So its been this whole time since I started the thread until yesterday that I've been way to busy to even look at the car. I went to the basics and checked fuel pressure first - very little pressure both at ignition on and idle. Thinking this is odd as the previous owner fitted a brand new fuel pump and I'd already changed all the vacuum lines as my first port of call I looked at the fuel pump. Took it out, the terminals were loose so I took the pump into my garage to give them a squeeze with pliers and while doing that I noticed that there was no jubilee clamp on the hose from pump to fuel pump housing outlet.

Long story short - I put a clamp on, got a bucket load of glorious fuel pressure and a perfectly running engine.

The fuel had been going up the pipe from the pump and leaking out around the edges and just going back into the tank due to a lack of hose clamp. I think that originally it was running badly due to broken vacuum lines, and air leaks which I fixed for him when he owned the car but shortly after his original pump failed, he fitted a new one but missed off the clamp causing a massive loss of fuel pressure and a bunch of issues. He then gave up n the car after the starter motor failed which is when I was given the car.

So I got myself a 325ci in exchange for half an hours work and a jubilee clamp that I found in my toolbox. I'd say that's a win. Now I just have to tell him that it's cost me nothing to repair and he basically gave me a car because he didn't fit a hose clamp......