bad hesitation / lumpy acceleration

[ccr32]

Afternoon all,

My 3.0si has all of a sudden developed some bad hesitation under throttle in any gear and under any load. When accelerating in any gear (most noticeable in lower gears from low rpm), the car noticeably flat spots and then picks up again at several points throughout the rev range, a bit like as if the TCS was cutting in on a slippery surface.

I initially attributed this to a bad batch of fuel, as having filled up the tank from a particular filling station, the problem appeared within a few miles, and then went away again once I refilled the car from another station.

However, after another long drive at the weekend and using most of the “good” fuel, the problem has reared it’s ugly head again.

I have subsequently booked the car in to be looked at as I really would like any major issues rectified before the warranty runs out in June! I have also carried out a throttle reset as is described on here – xxxxx. After doing the throttle reset, the problem was still there, though for no explainable reason, it didn’t seem to be there the following morning when going to work!?

Doing a bit of research through older problem posts on here, it sounds as though it could be any one of the following:

1) Faulty DISA
2) Faulty VANOS
3) Coil pack on the way out
4) Dodgy fuel pump/bad fuel

Does anyone have any words of wisdom for me before I am put in the hands of the ever-helpful-and-knowledgeable folk at my local stealership?

Not sure if this would be related to it either…. (hissing noise my car also makes when the engine is warm) - http://www.z4-forum.com/forum/viewtopic.php?f=3&t=13191&p=197935#p197935

Thanks in advance,
Calum.

 

[jamiez]

Number 3 based on the symptoms your describe

 

[ccr32]

Number 3 based on the symptoms your describe

Thanks. Should this have thrown a fault in the OBD? I haven't seen any lights appear on the dash as yet...

 

[AlanJ]

Agree - go for No 3 first

 

[Shipkiller]

Based on your write up, the DISA would not cause this issue, due to the fact that it happens at all RPM's and gears.

Your VANO's could do this.
It is possible that you have a bad coil.
You still could have some bad fuel in the tank.
It also could be a faulty Crank Position sensor or a faulty MAF.

The real factor is that is does this under all loads and RPM's. If a coil were to go bad like this, I would expect a CEL light since it would cause a misfire.

Since it is under warranty, don't do anything to fix this issue.
Let the dealer see how it is driving and responding, then they (the dealer) can read the DME and see if there are some minor error codes stored but are not throwing a CEL.

 

[Zedrider]

Have you checked the obvious like a bad plug and loose plug leads? How long have the plugs been in?

 

[ccr32]

I had a quick poke around the engine bay to see if I could spot anything obvious though couldn't find anything that stood out - I'll check the plugs and leads again though.

As had been said though, I shall not be performing any major surgery myself as it's under warranty still. The slightly annoying (or good, I guess) thing now is that it's seemingly stopped doing it, and so will be impossible to show anyone at BMW what it was doing.

Thinking that I'll run it down on fuel then fill it up again from somewhere different just to try and eliminate bad fuel, then see if the problem is still there.

Thanks for your help thus far though, I'll keep you updated on what happens next!

 

[jamiez]

Very much doubt this be bad fuel in this instance as a decent amount of fuel has been allowed to go through the system
Also highly doubt it to be a "loose plug lead or bad plug"

Im confident on a bad coil

as for OBD errors - you may get something on the dash either the ENGINE or EML light if i remember correctly.
When i had this very same issue in my old e46 (3 series) i got lights on the dash intermitantly

good luck and keep us posted

What the year and whats the mileage on your 3.0si?

Cheers
Jamie

 

[ccr32]

it's a '07, and has done 21k miles.

Thanks.

 

[brucelee]

Hi, I'm suffering from the exact same issue with my coupe - did you resolve this problem?

 

[Scooba_Steve]

Hi, I'm suffering from the exact same issue with my coupe - did you resolve this problem?

Buy a code reader and check to see if there are any thrown up - cheaper than paying someone else to do it your issue could be unrelated and you wouldn't want to replace anything unnecessarily.

 

[brucelee]

No codes being shown! I once got a knock sensor code thrown back but I put this down to bad fuel and cleared it and it hasn't shown since. But the hesitation I find only seems to appear during damp weather and it doesn't feel like a misfire, more like the ECU is stopping fuel or something. I've attempted the reset the throttle position in the past and I can't tell if it worked or not as this issue is fairly intermittent

 

[brucelee]

Anyone? Feels like a kind of pulsating surging

 

[brucelee]

So i just checked for codes with my obd reader and I have p135b (knock sensor) and p1554 (one of the vanos solenoids). I've had both errors before. When i I had the p1554, I cleaned both solenoid and the error went away. When I got the knock sensor error I just cleared the code and put it down to bad fuel, plus, I could reach both knock sensors to inspect them.

Any idea what the next course of action is? Could one code be causing the other? Ultimately I guess I could buy new vanos solenoids...

 

[Scooba_Steve]

I had a VANOS solenoid issue, cleaned it and it went away for a while then came back. £80 new from BMW so replace it, no issues since.
The workshop procedure is to swap the solenoids to see if the fault follows then replace. I didn't bother with that and I only did one of them rather than both.

 

[Ed Doe]

Scooba_steve what were the vanos issues you had? I've always had a slightly lumpy idle on my coupe, and recently the throttle has seemed a bit hesitant. Switching the AC on seemingly has quite a noticeable effect too - the throttle seems more laggy...

Just considering getting mine done now I've read the above!

 

[Tr1ckster]

Scooba_steve what were the vanos issues you had? I've always had a slightly lumpy idle on my coupe, and recently the throttle has seemed a bit hesitant. Switching the AC on seemingly has quite a noticeable effect too - the throttle seems more laggy...

Just considering getting mine done now I've read the above!

I just did a post on this in the main forum mate. Mine was vanos.

 

[brucelee]

Ah ok, so the VANOS issue only seems to affect the pre-facelift engines (not N52)

 

[Scooba_Steve]

Scooba_steve what were the vanos issues you had? I've always had a slightly lumpy idle on my coupe, and recently the throttle has seemed a bit hesitant. Switching the AC on seemingly has quite a noticeable effect too - the throttle seems more laggy...

Just considering getting mine done now I've read the above!

My VANOS solenoid symptoms were a hesitation at steady speed and throttle setting, for a fraction of a second it was as if the car cut out.

 

[brucelee]

So a bit of an update from me. Today I replaced the oil filter and oil. I also cleaned the MAF and both VANOS solenoids (and swapped them round afterwards) and so far code p1554 has not reappeared. Although the p135b(knock sensor code) keeps coming back. I also added some injector cleaner to my tank of fuel.

Any more ideas? I took it for a drive earlier and I couldn't recreate the hesitation or surging but the presence of the error code still worries me.

Oh, another thing: I checked the o2 sensor voltages for both pre and post cat and neither seemed to be oscillating when checking the live values... That doesn't seem right?! My car has done around 74k miles by the way, now.