Strange behavior after cam change

[wcelliot]

Hi!

Long time lurker; first post. I apologize for the basic questions, but my mechanical skills are old-school and low tech...

Subject is an '89 325i. Mechanically stock except for a Dinan chip and Ireland Eng. exhaust. About 140k on it.

To get a bit more performance, I was prompted by a local shop (that does mostly European restos, but has a young BMW guy on staff) to do up a fresh head with some minor porting and a slightly stronger cam (a Schrick "280"... which I assume is actually a 284), rockers, springs, etc.

Well, all of that was done and I picked up the car last night. It does not at all perform like I anticipated.

The bottom end is very strong... stronger than before... but the car seems unwilling to rev. It will pull to redline, just not very quickly.

It feels for all the world like a much larger/stronger engine, but one pulling a trailer.

My first thought would be that the cam is off a tooth, but the shop says that this is unlikely because the car would not run as well as it does. They are recommending that I unplug the computer for an hour or so then later unhook the battery for another hour or so.

Thoughts as I move forward with this?

Thanks!
Bill

[browntown]

I would think your chip needs to be programmed for such a change, but I know nothing.

[pdx 528e]

Your mechanic's suggestions will reset the ECU, which may help. However I would think that anyone changing a cam, going by a factory shop manual, would have disconnected the battery as its just a good practice.

What condition is your O2 sensor in? Did the engine have any driveability issues before this upgrade? Momentarily try swapping ECUs or chips (to stock maps) if you have one to rule out the issue of a faulty control unit. Test your TPS sensor per Bentley, along with coolant temp sensor and AFM.

I mostly know motronic 1.0 basic, so I doubt I can be as helpful as some of the others on the board who have B25s.

PS: Don't give too much credence to the idea that a timing belt a tooth off won't allow the engine to run very well. Someone on the Mye28 board has an 83 528e which a dealer had serviced. They were off 1 or 2 teeth. It ran fine but was less powerful and smooth.

[wcelliot]

Thanks... I would have thought that as well and was a bit surprised by the suggestion.

As far as I know, the 02 sensor is okay. Except for a slightly unsteady idle the car pulled strongly at all points...

I do have the stock chip I can swap back in... and I appreciate the other troubleshooting suggestions (which I can also do...)

It sounds like I shouldn't be worried about the cam being a tooth off?

Thanks!
Bill

[pdx 528e]

Thanks... I would have thought that as well and was a bit surprised by the suggestion.

As far as I know, the 02 sensor is okay. Except for a slightly unsteady idle the car pulled strongly at all points...

I do have the stock chip I can swap back in... and I appreciate the other troubleshooting suggestions (which I can also do...)

It sounds like I shouldn't be worried about the cam being a tooth off?

Thanks!
Bill

To be safe, pull the distributer cap and check the alignment arrow for the cam with the arrow on the harmonic balancer. I have a smooth balancer so I can't tell you exactly where to look, however I assume the gap in the teeth might be Top Dead Center on yours.

I added an anecdote about the belt on my last post.

Good luck!

[StereoInstaller1]

In the old school Chevy world, cams are usually cut to provide as much as 12 degrees advance, and the sproket can be used to advance or retard 4 degrees, or left stock.

The point is that virtually ALL aftermarket chev cams are NOT cut to stock cam timing specs. Makes me wonder if the same applies to Shrick.

What you are describing sounds more like a cam timing issue than anything.

I cannot seem to find much info on Dr. Shricks' cams...everyone says "They are the best" but no one says why. They list 272 and 282, but no 280.

I wonder if they are cut to provide additional advance or retard, and then your tech got fooled...I dunno. Maybe an adjustable-timing cam sprocket?

Keep us posted though, OK?

Luke

[StereoInstaller1]

Oh yeah, and as far as an ECU reset...I say no chance. If it is that far off, something else is wrong.

Didn't the tech test drive?

[wcelliot]

Update: Reseting the ECU made a LOT more difference than I thought it would. The car pulls much more strongly, but still feels kind of flat once it gets "on cam"... but at least now I can feel it get "on cam"....

Of course, now the idle is all strange... dropping to 500rpm, being bumped to 1000, then falling back to 500....

Definitely is running better/stronger, but still feels "restrained".

The tech admits to only driving it around the block a couple of times and never really getting on it....

Bill

[nando]

a chip programmed to work with your cam would help, but otherwise I would check to be sure that the engine is running properly (no vacuum leaks etc.) and that the valves are adjusted correctly. as far as the idle, with a hotter cam you want to idle higher; the ecu is just trying to adapt to the cam and is having a hard time - the idle should get smoother over time though, and not wander as much. it took mine about 2,000 miles to stabalize..

I still stand by my statement that regrinds are a waste of money, I'd rather have a stock cam than a regrind...

[Erick]

My god, they put an eta engine in your car! o.O

[StereoInstaller1]

I still stand by my statement that regrinds are a waste of money, I'd rather have a stock cam than a regrind...

He said it was a Schrick.

Luke

[wcelliot]

Thanks much for the info... the more I drive the car, the better it's getting... I assume the ECU is "catching up"?

However, since I'm driving it a lot, I've realized a new issue (one that I had noted on the first drive but thought it was because everything was new...) I'm getting a large cloud of smoke on startup... even if the car has sat for only an hour or so. This was not an issue before... and I wouldn't expect valve seals to leak by that much in only an hour... thoughts?

Bill

[pdx 528e]

Thanks much for the info... the more I drive the car, the better it's getting... I assume the ECU is "catching up"?

However, since I'm driving it a lot, I've realized a new issue (one that I had noted on the first drive but thought it was because everything was new...) I'm getting a large cloud of smoke on startup... even if the car has sat for only an hour or so. This was not an issue before... and I wouldn't expect valve seals to leak by that much in only an hour... thoughts?

Bill

Head gasket might be leaking oil into cylinders. What color is the smoke? If your injectors are leaking, it could explain the startup cloud. Also, do you smell gasoline in your oil?

[wcelliot]

Smoke is grey/white. Now that I think about it, it sounds a lot more like burning coolant (epecially after just an hour shutdown)... there is not a strong smell of coolant though... nor oil. Just changed the oil today (even though they changed it twice during the install and cam break-in) and it was nice and clean...
Bill

[JRowe]

White smoke = water. You're probably losing coolant somewhere. Keep an eye on your coolant level to see if it drops.