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Old 03-13-2013, 08:54 AM   #1
AK65
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'01 325i auto poor power, excessive fuel consumption

Hi Group

Just recently bought an '01 325i auto, mileage 56000 miles (90000km).

The car is really delivering a very poor driving performance which includes:

Poor acceleration, very poor at low revs, not much better at higher revs (>4000rpm)
Poor to no throttle response on flat ground at about 2000 rpm (no acceleration just the consumption meter going into the roof)
Failure to hold speed at moderate inclines at about 2000 rpm.
Bogging and hesitation at about 1500 rpm.

Pull off is OK, but sluggish response (only moderate acceleration) even when throttle completely open.

Fuel consumption is wallet squeezing / suicide inducing at 16 l / 100km

I purchased a OBDII Bluetooth scanner, and first looked for fault codes. P1153 - O2 sensor Bank 2 Sensor 1 Volts High. Nothing else.

Although it is a good idea to change the O2 sensor, I don't believe that this is entirely the root of my problem.

While driving, I monitored the MAF and engine load parameters. What was interesting, was that the engine load parameter never went above 55%, even at 6000 rpm with the throttle wide open, in marked contrast to my friend's 330i which at the same revs and throttle was about 96%. The MAF peaked at about 90 g/s

So, questions are what is the likely fault? Should I look at:

Fuel pressure?
MAF sensor?
Double VANOS seals?

All help and opinions appreciated.
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Old 03-14-2013, 10:41 AM   #2
AK65
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As a follow on to this, for those who are interested, I no longer suspect the MAF sensor. The performance with the MAF sensor disconnected, was just as rubbish as before

So cross that one off the list.

I'm having the car tested on a dyno next week to see exactly how bad the performance is...

But maybe CAT's?

Anyone?
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Old 03-18-2013, 03:52 AM   #3
AK65
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Ok,

Seeing as I'm having a conversation with myself, I may as well continue. Hopefully a boffin will eventually chip in.

So what I've done further, is to run a compression test.

Results are: Highest 10:1, lowest 9:1 average 9.5. Spec is 10.5:1 Thoughts on this for a motor with 56000 miles?

Plugs look good, brownish grey, no carbon deposits or black soot.

I took the tappet cover off, and there's no sludge in the engine. Thank goodness for that. I did notice flat spots on the vanos cover bolt heads which would indicate that previous work had been done on the vanos unit.

Again, would a faulty Vanos unit throw codes? I mean, my motor is dead from 1000 - 3500 rpm. Bogging, flat spots and double kick downs required for acceleration or to hold speed on moderate inclines. But no Vanos or cam related fault codes at all.

If the valve timing was off by one tooth, say, would that be the reason for the lack of torque? Would that throw codes?

Other check items not yet attended to:

Fuel pressure
Blocked Cats
O2 sensor fault codes

Guru's, please help!

Cheers


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Old 03-18-2013, 04:34 AM   #4
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No guru here but check the cats and fuel pressure but it's probably not fuel pressure. If timing was off it would run like trash but more than likely throw miss fire codes. Could be a vacuum leak anywhere in the engine bay do a smoke test. Also check and make sure each plug is getting arch (pull plug leave wire attached have someone bump ignition) check all 6. Trans could be slipping but you don't state that so why would it be that? That is what I would check first..... GL
Edit: if I think of something else I will post for sure.

Last edited by Joshwa1234; 03-18-2013 at 04:35 AM.
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Old 03-18-2013, 04:52 AM   #5
AK65
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Hi Joshwa1234

Thanks for reply.

Correction to the compression figures, the numbers in psi are: Max 145, min 130, ave137.

I'm sue you meant 'spark' and not 'arch'. All cylinders are getting spark.

No trans slipping as it's an auto. Rather, engine labours in the lower rev range.

My earlier figures were bar figures but these don't exactly correspond to compression ratio. Also when I did the test I didn't hold the throttle open so I don't know if those figures are accurate...

Thanks. Car is going in tomorrow for full dyno test, so well see exactly how many horses have galloped away from under the bonnet. And what the power torque curve looks like....

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Old 03-18-2013, 05:21 AM   #6
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Very first thing to check when fuel economy is in question is the engine operating temperature.

See the 3rd link below in my signature, much view forum on a computer to see signature.

Also check the DISA closely, see first link below in my signature.

Check your long term fuel trims and post this info back for review.

Clogged CAT's can be an issue, usually only after car has been driven when running poorly for a long time. Exhaust back pressure gauge can test for this (usually around $50 USD), or some just remove the pre-Cat O2 sensors from under the hood and then drive the car a short distance.

Cam timing could be an issue. Static cam timing could be verified, then you would need GT1 or other type of software to run a VANOS test. This uses the cam sensors to monitor the cam position while the software advances and retards the timing.

Torque converter may be bad, but it does not quite fall into your description. The torque converter for the auto transmission would likely have a bad stator clutch causing the stall speed of the converter to be not working properly. Usually a bad torque converter will be out of the picture above 2500-3500 RPM?
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Old 03-18-2013, 06:04 AM   #7
AK65
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Hi jfoj

Thanks for the heads up. Great info.

The temp I don't think is an issue, seeing as the OBDII scanner indicates 96 deg C. Also I live in a warm climate.
I'll check the fuel pressure. Thing is, this car is 12 years old, and even with (supposedly) low mileage, age does play a part, I think.
I'll also investigate the DISA valve. Noticed a wheezing sound with the air filter off, which wasn't the usual sound I expect, certainly from old carb-fed engines. I also noticed a missing inlet manifold bolt, which says to me someone had the head off at some time, so reassembly of the inlet system may not have been optimal!?

I'm going to redo the compression test according to the Bentley manual (wet and dry). Fingers crossed, the figures I have are maybe low because of inlet restriction.....

Keep the group posted on my progress
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Old 03-18-2013, 04:30 PM   #8
AK65
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OK here are results of second compression test (wet and dry) and fuel pressure measurement...

Dry (in PSI):
1: 150
2: 145
3: 145
4: 145
5: 142
6: 135

Wet (also in psi)

1: 167
2: 175
3: 172
4: 175
5: 175
6: 165

In most cases, a difference of 30 psi or so, with cylinders that were down showing much higher gains when when wet. This does not look good, unless I overdid it and put too much oil in the cylinder, affecting the volume of compressed space too much....? He says hopefully!

Also, I measured the pressure in the fuel rail and it was 40 psi with just the ignitiion switched on, rising to about 45 psi when then motor was running. So, scratch that for the time being (although it could be a volume issue, as under load the engine will require more fuel)

So, I am left with the following avenues:

1: Rings are worn and motor is worn out (ouch!)
2: Vanos unit is faulty
3: Disa valve is faulty
4: CAT is blocked and the engine is choking....

Will keep you posted.
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Old 03-18-2013, 05:04 PM   #9
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I don't have a chart in front of me, but 90 g/s sounds pretty low. Given that running in open loop doesnt help, I would try to investigate the cats. The literally quick and dirty test is to take out the forward O2s and go.for a short drive.
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Old 03-18-2013, 05:29 PM   #10
scarede46er
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I guess it would be the O2 sensors. Your symptoms point to it. Change them if you have not already. They have a life of 100K miles. And yes, since oil is less compressible than air, your readings would be much higher if you dump a bunch of oil in the cylinders.

Last edited by scarede46er; 03-18-2013 at 05:30 PM.
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Old 03-19-2013, 03:58 AM   #11
AK65
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Hi, thanks for the reply.

The O2 sensor on Bank 1 no 2 seems to be faulty (Volts high). I've also lately got misfire codes on 4 and 5 and lean codes on that bank too. Yet the system seems to be running in closed loop using O2 sensors? How is it doing this for cylinders 4, 5 & 6?

After taking the covers off I noticed that the Bank 2 O2 sensors are not fitted, they seem to be connected to a blank units in the connectors themselves and their send value is constant 0.4 volts

Perhaps this is because we have less stringent emissions controls here in South Africa?

My colleagues 330i seems to have only one of his Bank 2 sensors connected.

Car is currently on the dyno, shortly I'll have results....

Also what I have not checked is fuel filter, which I assume may restrict fuel flow (and pressure) under load, but show good static pressure.

Still love the E46. Such a sexy car....

Next instalment soon....

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Old 03-19-2013, 04:27 AM   #12
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You need to get some form of software in order to read real time engine data and possibly record the data as well.

See this link here - http://forum.e46fanatics.com/showthread.php?t=967204

Bad O2 sensors rarely cause misfires. If you have misfires you likely have a fuel or secondary ignition problem.

As for your compression testing, this was a wise idea, however, I would not get too excited about the absolute measurement but more the variation. If your values are within about 10% of each other, I would not worry about anything.

You mentioned your fuel pressure was around 40 PSI, this is too low. Fuel pressure needs to be around 50 PSI. Do you know your gauge was accurate?

You really need to read over the first 3 link in my signature for idea and info.

If you are getting DTC's and CEL, get the freeze frame data and post it up for review.

O2 sensors could use to be replaced due to mileage, however, you need to monitor the O2 sensors with a software tool to really see what is going on.

Are you saying you have some sort of O2 sensor simulators installed??

This is a BAD thing on pre-Catalytic converter O2 sensors.

If your car has been running with O2 sensor simulators for a long time, I am not thinking you could in fact have restricted catalytic converters??

You need an exhaust back pressure gauge in order to measure the exhaust back pressure like this tool - http://www.amazon.com/Tool-Aid-33600...pressure+gauge

http://www.aa1car.com/library/exhaust_backpressure.htm

http://www.tuneruniversity.com/blog/...aust-upgrades/

You should also read over this link as well - http://forum.e46fanatics.com/showthread.php?t=954362

I assume your car only has 2 O2 sensors?? I believe most of the cars sold outside of North America only have the front 2 O2 sensors? But I could be wrong?

It is actually rather STUPID to disable most of the fuel control sensors in any car as it will DRAMATICALLY impact fuel economy, performance, emissions and possibly cause catalytic converter melt down in the end.

But this is usually done when people do not understand how the fuel control system in a car works and they "think" they know better.

Closed loop fuel control systems are actually pretty simple when all is said and done. The biggest expense and most difficult part to actually trouble shoot is the MAF and you have to be VERY careful not to put a cheap/imitation/clone/counterfeit unit on the car otherwise you will have a LOT of problems.
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Solve your misfires, lean codes, rough idle - http://forum.e46fanatics.com/showthread.php?t=897616

Fuel pump failures - http://forum.e46fanatics.com/showthread.php?t=929501

Temp Info - http://forum.e46fanatics.com/showthread.php?t=964491

Hidden OBC Menu - Check Voltage, Temps, Fuel Level - http://forum.e46fanatics.com/showthread.php?t=239619

E46/E39 GM5 Door Lock Info - www.bmwgm5.com

Lower hose fan switch O-ring - BMW #13621743299

Last edited by jfoj; 03-19-2013 at 04:35 AM.
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Old 03-20-2013, 02:03 AM   #13
AK65
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Hi jfoj

Thanks for that great info.

The 'missing' O2 sensors are the post cat. The reason I think it's factory fitted is 1. The blanks are fitted in the connector in a way that looks factory. No bodge.
2. The ECU is not complaining about the static values. It's like it's programmed to ignore them.

The car is still being dyno tested, indications are that the fuel pump is faulty. System running super lean. I've asked them to also check the fuel filter as well.

Hopefully were getting to the bottom of this.

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Old 03-28-2013, 09:17 AM   #14
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Just an update.

The car is still (!) in the shop. So far they have been very thorough and have found 1) Both pre-cat O2 sensors faulty, 2) Short circuit fault in the heater circuit for Bank2 sensor. Now it seems that the injector o-rings are messed up because the car is still running too lean. I presume they eliminated the MAF sensor as being faulty. So hopefully it will deliver the proper horses and torques by the time they are finished. They also checked fuel pressure and nothing wrong there.

Can't wait, getting very anxious to get my car back.
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Old 04-08-2013, 11:19 AM   #15
AK65
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More update:

Got the car back from the shop. New O2 sensors and injector seals certainly improved the situation, but the motor is still down on power. Torque is max 180 Nm, should be 240, and power is max 112kW, and should be 140kW.

I suspected VANOS seals, and changed them. The old seals were shot, but this did not improve the situation to my satisfaction.

I checked the DISA valve, it's working perfectly.

While I had the valve cover off, I noticed scuff marks on the torx nuts that set the VANOS timing. Further inspection of the engine reveals it's had a new cylinder head gasket fitted. Which leads me to believe that the valve timing has not been set properly on reassembly.

I'm sending the car in to have the timing set, this is the last roll of the dice. If this doesn't improve the power output, I'm out of ideas.

Thoughts? Here's hoping....
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Old 04-08-2013, 11:27 AM   #16
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Improper cam timing can and will impact power and fuel economy.

It is amazing how easily someone can screw up the cam timing when changing the cylinder heads on these cars!

Hopefully this will resolve your problem if they get the cam timing correct.
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Solve your misfires, lean codes, rough idle - http://forum.e46fanatics.com/showthread.php?t=897616

Fuel pump failures - http://forum.e46fanatics.com/showthread.php?t=929501

Temp Info - http://forum.e46fanatics.com/showthread.php?t=964491

Hidden OBC Menu - Check Voltage, Temps, Fuel Level - http://forum.e46fanatics.com/showthread.php?t=239619

E46/E39 GM5 Door Lock Info - www.bmwgm5.com

Lower hose fan switch O-ring - BMW #13621743299
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Old 04-11-2013, 01:49 AM   #17
AK65
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Latest Update.

Shop that checkedvthe cam timing said it was spot on :-( . They also test drove the car and said it drives like it should.

I must admit that there has been a marked improvement since the fuel issues were sorted, and minor improvement since I changed the vanos seals, but to me it's lacking something. I never noticed a lack of torque, power or bogging when I had the E39 523i manual with the M52TU motor, which had 20kW less than this motor.

So, I'm still looking and am all ears....I will be doing a 0-100km test to see where we are against the benchmark

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Old 04-11-2013, 02:11 AM   #18
frostbytez
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just a thought.. have you reset/cleared the adaptations lately?
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Old 04-11-2013, 03:21 AM   #19
AK65
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Adaptations? Could you elaborate further?


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Old 04-11-2013, 03:44 AM   #20
frostbytez
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you will need to hook it up to a pc or tool to do it...



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