Poor Acceleration With 540i - BMW Forum

ericmalkoc · 06-30-2005, 05:41 PM

Well, my 2nd topic in day! sorry! maintaince time...

I have had 100K service done at a local European BMW shop couple months ago...

They replaced the spark plugs with Bosch brand.

But lately, may be me, the car is not accelerating from idle/zero speed as used to be. I used to feel the power and take on any car from stop ..but lately, the car gets to a certain point and then accelerates...

Has anyone had such a problem? any fixes? Thanks again!

-Eric

Eric S. · 07-01-2005, 09:10 AM

Tough call. You don't mention your car's year, but NO 540 should ever be weak on acceleration. THe only time my '99 has felt flat was when my MAF sensor went bad.

Starting in 1999, there's a whole different Bosch engine management system, with electronic throttle and many other differences compared to 1997-1998. Since you're changing plugs at 100K, I am guessing you also have a '99 or newer. In my case, I had NGK plugs as original equipment, so right there something seems a little off, altho I imagine there must be an equivalent Bosch plug.

Another thing common to all 540's is trouble with vacuum lines/hoses. I know that when I changed my plugs, I had to unplug numerous rubber vacuum hoses stop the engine. So maybe it's possible something got damaged or didn't get reconnected correctly when changing the plugs.

Another thing '99's and up have is VANOS on the intake valves. If the vanos harness was disconnected during spark plug change and then not reconnected properly afterward, then that could be your problem as well, but I imagine that would trigger a code and a SES light.

LOS · 07-01-2005, 09:20 AM

Yeap, sometimes even the pros forget to connect thing back properly. I had my upper arm bushings replaced recently and the guy forgot to tighten a few bolts resulting in funny noises...

By the way Eric, I'll be replacing my plugs/boots hopefully this weekend. I hope not to find it to difficult. This will be my first time on a Beamer! The Camaro ('92 V6) had one plug that was a pain in the rear to get to and my Fiero ('88 GT V6, transverse engine) is no picnic either. Three plugs face the firewall!! Anyway, I have my manual and tools for the job.

LOS

Eric S. · 07-01-2005, 09:32 AM

Quote:

Originally posted by LOS@Jul 1 2005, 10:20 AM
Yeap, sometimes even the pros forget to connect thing back properly. I had my upper arm bushings replaced recently and the guy forgot to tighten a few bolts resulting in funny noises...

By the way Eric, I'll be replacing my plugs/boots hopefully this weekend. I hope not to find it to difficult. This will be my first time on a Beamer! The Camaro ('92 V6) had one plug that was a pain in the rear to get to and my Fiero ('88 GT V6, transverse engine) is no picnic either. Three plugs face the firewall!! Anyway, I have my manual and tools for the job.

LOS

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It's not a tough job at all. What usually happens, though, is that you'll find that your valve cover inner gasket has been leaking oil into the rear spark plug wells and that you'll probably also need to change those valve cover gaskets (a little tougher and more involved for sure). It's really better to do it all at once if that's the case. If so, just buy your gasket sets and rubber grommets now and do both at once since you pretty much have to remove the COPs to remove the valve covers anyhow. I felt like an idiot when all the work I did changing plugs was re-done a week later when I changed out the valve cover gaskets.

You can check for oil in the wells visually fairly easily. Remove the two little bolt covers on the valve cover plastic trim panels, and then remove the 10mm bolts and covers. look carefully down into those rear-most plug wells (if you can see past those COPs). I'm betting you'll have oil in there if you haven't changed the gaskets in the last 50K miles...

PS - I once had a Camaro, a 1985 IROC-Z, and despite the stereotypes it was a good car in that I had the tuned port injection combined with 5-speed manual (not available from the factory until 1987) and a custom chip. I also had Konis and Recaros. It had been owned by a GM test engineer and so it had some other cool custom touches as well. Plugs on that car were a bear. My bud who had a 1988 Grand Prix with the V6 complained that in order to get one of the rear plugs out, the upper engine mount had to be removed and the engine rotated with a breaker bar. Thanks GM.

LOS · 07-01-2005, 09:41 AM

Thank you for your comments Eric. It's always good to know what else to look for when replacing plugs.

LOS

LOS · 07-06-2005, 11:58 AM

Eric, replaced the plugs & boots last weekend. The whole job took a bout two hours and was simple. I do recommend to buy a telescopic magnet just in case any hardware falls inside the plug well area. I dropped a nut inside and was lucky enough to have one of those handy.

I was glad to see no oil on the plugs or anywhere else. The boots were in good shape but decided to change them anyway... Three weeks ago I discovered the power steering hoses were leaking a bit. I decided to have the shop do it, it was expensive ($525.00 ouch!!).

Once again, thanks

LOS

ericmalkoc · 07-06-2005, 05:18 PM

Hey Guys, Thanks for comments.

My car is 1998 E39 built 10/97...I checked with my mechanic last week, he indicated that no accx problems. everything is Ok..I think I got used to it so fast :P