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What could cause a loss of power ????

3K views 20 replies 8 participants last post by  ztitans1 
#1 ·
My 97 528i with 220k has been a project....its never not ran or had any major issues, its just an aging car. I've done all the usual preventative type stuff (transmission service, O2 sensors, CCV , alternator , belts and hoses, replaced a broken header and gaskets, front wheel speed sensor, new plugs, ect). I do believe I need a VCG as I had oil in the plug channels and the car will sometimes smoke a little bit. My concern is that my car used to really respond to the gas pedal. Now it seems that rather Im at 1/4 pedal or 3/4 pedal its picking up about the same. Its not so much "lagging", its just not responding with the same "oomph !!! " as before. What might cause this ? Thanks for taking the time !
 
#3 ·
The two things that would usually affect engine performance are the DISA and the VANOS. The DISA modifies the intake length and the VANOS adjusts the timing, both to increase low end torque. The 97 engine engine does not have a DISA and I think it has a single VANOS. The seals should be replaced to restore the variable timing system. See the Beisan website for more info.
 
#5 ·
When the cats get bad enough, they typically cause random multiple misfires, due to back pressure.

One tends not to notice the performance loss due to VANOS seals, as well as failing cats. Do the cat rattle when struck with a rubber mallet?

A back pressure tester can be fitted to the pre-cat bungs.
 
#6 · (Edited)
The first thing I would do is New MAF and Air Filter because they are cheap and very easy DIY. If that doesn't work start doing the vanos and hard stuff.

In my 540i my Maf died twice so the engine goes flat around 200 hp instead of 282 hp
 
#19 ·
+1. Just because its a new part does mean you have a GOOD part.

I would also replace the rubber boot going from the MAF to the throttle body/housing. They always crack and cause vacuum leaks.

Only other thing(s) is maybe your fuel filter(with built in fuel pressure regulator) and maybe fuel pump not delivering enough fuel when under load. ?
 
#7 ·
MAF done about 6wks ago....air and cabin filters at the same time. I need to do the vcg so Im gonna go ahead and do vanos. Now , do I wanna do vanos seals or rebuild the entire vanos system ? I called an indy that I trust to check their price for doing vanos and vcg ....he says around $400 . Does that sound right ??? I know I could do it myself, but after parts and tools Im probably lookin at around $200. It may be worth the extra $200 for that warranty ....and plus it seems like a bit of a headache.
As far as my cats .... I don't know, I guess I'll grab a rubber mallet and give em a smack. What are the pros and cons of aftermarket cats ? I mean, if my cats were bad and I installed magnaflow or Walker cats would it be an improvement ????
 
#11 ·
Now , do I wanna do vanos seals or rebuild the entire vanos system ? I called an indy that I trust to check their price for doing vanos and vcg ....he says around $400 . Does that sound right ??? I know I could do it myself, but after parts and tools Im probably lookin at around $200. It may be worth the extra $200 for that warranty ....and plus it seems like a bit of a headache.
There are only two things you can replace on the Vanos (single or double). One is the seals, which are all bad due to the material issue. These must be replaced. The second is the bearings. These only need to be replaced if the Vanos is rattling, usually on cold startup. This is a bit more work. Another option is the Dr. Vanos, which is a complete rebuilt Vanos. It's just a straight swap. That's $250, after core charge, but saves about 2 hrs since you don't need to replace the seals or the bearings.

$400 sounds a bit low for a Vanos seal replacement. It takes me about 5-6+ hrs to do this job and I have done it multiple times. I cannot see anyone doing it in under 3 hrs, given the amount of parts that need to be removed. The parts (seals $60 + VCG & grommets $45) are over $100. That leaves less than $300 for labor. Here in NE, that'll buy you about 2 hrs of work. So it seems low to me.

Honestly, I would recommend doing the Vanos job yourself. Yes, it will take you 6 hrs but then you get to see the inside of your engine. For folks that don't get to do these kinds of things, it is kinda neat looking inside that I6. The only special tools required are the fan clutch tool and 32mm wrnech (~$30). You should have everything else. While the $250 savings is nice, the satisfaction is immense. :D This is my favorite DIY as the benefits are usually very noticeable. And the Beisan instructions are amazingly goof. A very high ROI!
 
#8 ·
Any code? Could it be a vacuum leak? When you did the head gasket did you get the head milled Down? Heads can get warpped when they are taken off
 
#9 ·
Haven't done head gasket ...had a broken exhaust manifold header that I replaced. My cats look bad. the heat shields are just kinda hanging on for dear life lol....it looks like the previous owner maybe tried an adhesive to hold them (heatshields) on...from rattling maybe ??? Or they're spooging some whitish, rusty lookin crap outta them lol... I don't know man... its dark. I'll check again tomorrow, Im beat...long day. Thanks for taking the time everyone. I'll update soon.
 
#15 ·
Well...actually what you said was only special tools needed were tools to remove fan , which I have, and according to beasian diy I will need the timing tools .... Im just wanting to make sure I get everything that I need ordered . Thanks again !tools.....
 
#17 ·
Definitely has crossed my mind.... I definitely have a leaky vcg and a couple deteriorated plug boots so this is a possibility. I plan on doing the vcg when I do vanos seals so I guess we'll never know what the actual cause was :cry: , but as long as it's fixed I'll be happy :bigpimp: ! I appreciate the inp:thumbup:ut
 
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