My first post in this section, intermitant hesitation?

B

BobZ4

Member
After 3 weeks of ownership i have managed to avoid posting in this section, to be fair i knew it was a matter of time.

i have a 2003 Z4 3.0 Manual and I still cant decide if it is in my head or not, but on hard acceleration my car feels like it occasionally bogs down and hesitates over 3K rpm. Usually shifting up it drives no problem, here is a list of what i have checked.

1. Disa, taken out and cleaned with carb cleaner nothnig loose.
2. Ignition coils, check for resistance levels and all are around the same resistance 1.1 within level.
3. Spark plugs, took them out and checked for fouling all plugs checked out ok.
4. Cleaned the MAF with Carb Cleaner and allowed to air dry.
5. Changed air filter.
6. Scanned for codes but no fault present, even visited a local garage and they found no codes FOC.
7. No rattles from the engine at all and no visible leak from the Vanos so i guess the Vanos is ok.
8. I put in some Wynns Injector cleaner at the last top up to see if it may be clogged injectors.
9. I took off the oil cap with the engine running, there was some suction but not strong so i guess the CCV is ok.

The BMW master tech took a drive and could find the characteristics i was talking about with me in the car, he recommended bringing the car in for a DME software update though there were no guarentees this would resolve my problem at a cost of £100. Any thoughts? Could it be something to do with the throttle position sensor or a vaccum leak?
 
Thanks, I tried that turn to ignition but dont start for 10 seconds then off for 10 seconds then start. It does improve for a while.
 
Same engine, same year, same problem as you, same temporary fix with ignition reset. VANOS is the cause of this (you cannot have any visible signs of their damaged seals). Will need replacement eventually. Running high octane exclusively does reduce the occurance though in my case.
 
Thanks for the reply, believe it or not my threatening the car with a visit to the dealer did the trick. Its behaving again, I am going to leave it for now.
 
possibly throttle position sensor or crank position sensor but usually i would put this down to faulty MAF (despite you cleaning it)
Tricky one as its intermitant which means fault reader will only pick up if the offending bit is actually faulty or misbehaving at the time of the check

hummm

Jamie
 
Well, I have had a call from BMW today and they have found a problem (which in my eyes is a good thing, as it means I won't be charged!) - it's been diagnosed with (and I quote) a faulty "Nitrogen Oxide" sensor...

...now I'm pretty sure my car didn't come as standard with NOS, so I'm going to assume that I either heard incorrectly or he meant an Oxygen sensor.

Bad news is that it is a factory order part, so my car is going to be with them for the best part of another week... :( Still, if it's all sorted when it comes back, then I don't mind so much.

Will report back again once I get the car back.
 
So did the O2 sensor fix the problem?... strange thing is that I have exactly the same issue, but i replaced my 02 sensors, DISA, Vanos with updated seals, spark plugs, secondary air pump...which has nothing to do with this, and the problem is still there... The 02 sensor is for emmisions so it should not effect the drivability of the car, right?... Please correct me if im wrong. I will be searching for someone to swap a MAF for an hour or two and see if this fixes the problem. If there is anyone located in the Los Angeles 626 area please let me know and I will gladly pay a "rental" fee :thumbsup:
Please let us know if your problem was resolved
 
Well, I've finally got the car back - a week and a half seemed like a long time for it to be away!

And yes, happily I can report that the o2 sensor appears to have rectified the fault - the car now feels like it should do - pulling consistently throughout the rev range (with a bit of top-end VANOS kick) :D

When my car had the fault it only reared it's head intermittently, and when it was not hesitating I can say now almost for certain that it was down on power - feels so much better now.

SSG - I'm no technician but I can only guess that o2 sensor was sending false signals to the ECU, which in turn was incorrectly adjusting the fuelling making the engine either bog down or hesitate.

I'll of course report back again if the fault comes back, but I am a happy chappy for now :driving:
 
I recently replaced the oil seals on my vanos to see if it improved my intermitant hesitation, i thought it did at first but nope its still there. So far i have replaced the ignition coils, replaced the oil seals on the vanos and cleaned the MAF with CRC cleaner. My car is sometimes a bt chuggy pulling away when cold, no engine lights or fault codes.

Anyone have any other ideas?
 
I have the same, but much has improved with a new disa. Vanos seals are next as well as O2 sensors. Just replace both of them and youll see, costly but at least you can tick it off from your list and sleep well that they wont eventually fail you. You can also keep the old ones as relplacement if the new ones dont fix it. :) I can tell you this though - my dads touareg used to run like crap - hesitation, misfires and no power - new O2 sensors did the trick even though the dealer kept yapping that it is not at all O2 sensor related :)
 
Thanks for the reply, I am going to replace the disa next for the following reason. I took out the disa valve to inspect it and i didnt think the movement of the flap was smooth enough it felt like it was catching on the mechanism. I cleaned it and used some WD40 on the moving parts, i then put it back in. After doing this i reset the throttle with the 10 second trick, the idle \ acceleration was silky smooth after that and for most of today but after work it felt a little rough again. I recon the valve is faulty or i have a vac leak where the valve joins the inlet manifold.

The disa is out of stock in the uk and germany, i guess i will have to wait till it arrives.
 
Guys I am totally confused now, I cleaned my Icv at the weekend. Since then I also reset my throttle adaption, the car now feels smoother and the is next to no hesitation. My dilemma is do I still get the dme sw update tomorrow, what do you think.
 
Hi, webrits: how much did the re-flash cost? Can any garage do this? I'm having the exact same problems with my coupe. I am getting the P135B error (knock sensor), so I'm not sure if my knock sensors need replacing or if it is something else. My problems seemed to start one tank after starting to use V-power.
 
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