E34 525i (Auto) Surging at speeds between 55-60mph

[iamjunior7]

Hi Everyone!

I am Junior and I've owned my E34 1994 525i (Auto) for about a year now and I love this car! My E34 has been rock solid and fully dependable and hella fun to drive, especially with the little upgrades I did to the suspension... Bilstein shocks, H&R springs and overhauled suspension components (Tie Rod, UCA, LCA and all that jazz...).

So, as of lately I've been getting this really strange SURGING between 55-60MPH. I've done some research and found this article:

http://www.bimmernut.com/forum/showthread.php/34852-Solved-my-E34-surging-problem?highlight=e34%20surging

Once this weekend is over I'll have time to check what everyone was talking about in that post. So, I'll go over TPS, O2 Sensor and CPS.

But for now... If anyone has came across this problem please let us know what you did to solve it.

Also, I've posted a video so you can have a visual of whats happening. Here is the link:


http://youtu.be/-mMgJtDuAHI
https://youtu.be/-mMgJtDuAHI

Thanks for you help in advanced!
Peace,
Jr

[632 Regal]

Wow that is some serious surge going on there!
(I edited your video link to work, on V-bullitin you have to remove the S in https)

Does this only happen at that speed or will it happen in a lower gear at the same RPMs? Sounds like the ignition is completely shutting down to 2600 rpm and then back up to 3k.

Is the engine completely warmed up? Couldn't see the guage. My M60 will do the surge thing at the same RPMs when not completely warm, some sort of rev limiter.

[iamjunior7]

Thanks for the reply and fixin' my video link!

Yeah, it's a trip when it happens haha! And it's rather smooth, no crazy vibrations or anything. You can feel the dips (loss) in power as the RPMs drop but it normalizes pretty quick. This actually does only happen at those speeds and RPMs and the car was warmed up in the video. It does happen when cold but not as obvious.

I'm looking at diagrams right now so I can figure out where the CPS is located and I can double check the "bolts" OnZone was talkin about in the thread I originally posted. I'm confident its not my O2 sensor because my car just passed smog with flying colors... So I'm leanin towards loose bolts or the TPS until I can find more info.

I've read that several people were asking for the location of the CPS. If it's in a convenient spot for me I'll snap some shots for y'all.

[632 Regal]

I think your chasing a shadow. I wouldn't bet my life on it but would bet a bad intake leak combined with O2 sensors combined with spark plug boots with the BROD. Start with checking the plug boots (and plugs) If the boots have the BROD replace them. If the plug holes are full of oil replace the valve cover gaskets.

Actually working on a slight miss myself and it's all in the air I have many issues going on. The oil pump is probably not even attached which would be half the cause plus the CCV in back of the intake leaks so I ordered a new one along with intake gaskets and a Throttle body gasket. Intake is full of oil.

As for bad O2 sensors... Nikky had almost 300K with the original and I always had stuff fixt before replacing those. I never replaced them infact. She used to pull like a freight train, was a nikasil and could have been infact a 4.0 litre. can't check now tho.

Back to basics since we don't have OBD2.

Surging is almost allways an intake leak.

[whiskychaser]

Pendulum shifting?

http://plaza.ufl.edu/rroopnar/attachment%5B1%5D.pdf

[iamjunior7]

Dang, now that you mention it... I remember a while back a friend telling me I should replace the intake boot cause of small cracks he noticed. I'll be the happiest person alive if a new intake boot fixes it. But, I'll take some carb cleaner or starting fluid and start spraying around to see if I can spot any leaks. As for the spark plugs, ignition coils and boots those are fairly new but it wouldn't hurt to pop them out and have a look. I did, my valve cover gasket last year with a couple other things... Possible premature Valve cover gasket failure? we'll see... Thanks for the info again!
I should be back in town Sunday night and ready to dive into the abyss Monday morning.
cheers

[iamjunior7]

Pendulum shifting?

http://plaza.ufl.edu/rroopnar/attachment%5B1%5D.pdf

Awesome stuff! Thanks so much.
I'll thoroughly read through this in the morning and let you know if I have any questions cheers

[genphreak]

Solenoids are a common fault on old trannies. You may be able to read a fault code for it though. The trans also has a temperature sensor in there that fails too, think about doing that if you go in.