Bad hesitation below ~2K rpms

[ronpapworth]

I have been having a hesitation, no matter what gear I am in in my 5 spd 98 328i. It seems like it's running on 3 or 4 cylinders until I get to about 2200 rpms and then it comes to life. Typically I would think it's the AFM, but does anyone know what else to check? Im getting no check engine light. It seems to be worse when the air is on also.

[Waveho]

Seems to be a sudden epidemic. I'm having the same problems all of a sudden. Virtually the same symptoms. See other string on this site.... Good luck.

[Pirate_copy]

I had this on my 328i too, it drove me mental.

I added a custom CAI (K&N), added a mongoose exhaust and switched to Iridium plugs. they all made a little difference but was still there (and still is to some extent).

One day i was messing around in the engine bay (as you do) and i noticed there was a small rip in the intake boot (black, ribbed pipe between the airfilter and the throtle body), i replaced it, which cos like $30 and it is MUCH MUCH better.

I dont think you will ever get rid of it completely unless you get a power boost vavle to up the pressure in the fuel rail. I have one sitting in my workshop as we speak so will let you know if it helps when i get it fitted.

Check your air-filter and intake boot is my advice. Straight 6 engines are known for their low power below 3k revs apparently. I would say "keep above 3k revs" but that is impractical and in most cases.....impossible!!

Also, i know i KEEP saying it, but are you sure it is not the stupid bloody CDV. it is a valve that lets the clutch engage slowly no matter how hard you boot it off the line. i suggest this a lot because many people dont nitice it does it until they are told....me included.

check this for a better description - http://www.bmw325i.net/rev_cdv_removal.shtml

[Waveho]

I have a date for a complete tune-up later today. Problem is getting worse, and seems to be running on only three or four cylinders now, noticable during accelleration at any speed. The car probably never had a tuneup, as the previous owner took lousy care of it. I'm hoping that's the problem. It was running so well after I replaced the fuel pump relay and O2 sensor. I hope it's not the fuel pump now....

I also noticed a tear in the mass air intake boot (seems to be a common problem), and also replaced that when I replaced the O2 sensor. I just don't understand this sudden problem, as it was simply running beautifully after the fixes....

[ronpapworth]

I hate when I do 2 things to a car before test driving it because now I am not sure which one of the two fixed it. I have a feeling it was the ORIGINAL plugs in it (that had 86K miles on them.) I did the fuel filter too and it had 13K on it, and was pretty clogged, but I have seen worse.

I have a folder of what was fixed on the car from 1998 to early this year. It appears the dealership wanted to do plugs 13K miles ago but "customer declined". I think I see why, the work order estimate was $665! Probably the reason the guy sold it. I have no idea if the plugs were done prior to 1998 and the 33K miles that were on it then but I doubt it. The plugs that I pulled out looked good, but they were NGKs that were made for BMW (they had NGK BMW R4 written on them)and they were 4 prong. Hell of a plug if it made it 86K miles. I replaced them with regular single prong NGKs I bought for 2.25 each. 14 bucks sure beats $665. Dealerships should be ashamed of themselves.

[Waveho]

Whew! Only $149 and 6 plugs, timing adjusted, and an fuel filter later and she's a dreamboat again. That was the problem for me: Apparently the plugs were pushing WELL over 100k miles, and the fuel filter, well, several years and untold miles. Shoulda checked these things earlier but there were other pressing things. Thing runs like brand new now, and earlier today it was Yugo-esque. That's a relief. I would have put good money that it was the fuel pump, or worse.