'91 535i running great, but hitting rev limiter at 5500 RPM?

[paanta]

All,

My new-to-me 535i seems to be hitting the rev limiter at 5500 RPM. It pulls very hard from 3K-5K, then tapers off fairly quickly and hits a hard limit at 5500 RPM. I've not tried actually holding the car there and trying to drive past it, but I know what a rev limiter feels like.

So...
A) The tach is off by almost a thousand RPM. I've got an indicated ~85mph when it hits the limiter at 5500 rpm in 3rd. Is that the normal road speed you'd expect at that engine speed?

OR

B) The chip/dme is wacked out. It's got a Mark D'Sylva chip in it from the previous owner. Maybe it's bad?

OR

C) There's some sort of fuel problem that is happening consistently and abruptly at 5500 rpm, given the impression of a rev limiter. That doesn't seem the case, since the car is really strong and running fine otherwise.

Not being super familiar with the fuel injection in these cars (though I have lots of experience with the E28 + VW/Audis) I don't know if there's some common avenue for this sort of freak out.

It really almost feels like the tach is off. The whole power band seems shifted a thousand rpm compared to the feel of my e28 535is w/ Jim Conforti chip which is still accelerating pretty hard at 5500 or 6000 rpm.

Anyone have this happen before?

[paanta]

Fault code 1222 Lambda Control 1 after a hard drive. Cause of problem, caused BY problem, or unrelated? If the chip were messed up, suppose it could throw the mixture off enough to cause that?

It's definitely limiting itself to 5500-5600 rpm. It'll hold at 5600rpm if you floor it third and just leave it there....I hate doing that sort of test to a 220K mile old engine, though.

[Ross]

If the method of limiting the revs is cutting off spark then it might explain the code, raw fuel being dumped into the exhaust stream.
I can't think of a mechanical fault that would cause that symptom and fuel starvation from waning pressure would be more gradual I'd think.
Do you have another ECU available to swap?

[paanta]

Yeah, it definitely feels very abrupt. It will _not_ rev past 5600 rpm.

I don't have another ECU now, though the previous owner is hopefully mailing the stock eprom to me.

I've been in touch with Mark D, and he suggested it might be a wheel sensor even though there's no traction control? What all do those get fed in to on this car?

Thanks for the help. This car is a bit of a black box to me right now. Hopefully it's reliable enough that it always is.

[632 Regal]

Limiter could be ignition related. What do the plugs look like? Check the plug boots and coilpacks for signs of arching. Oil in the holes can cause shorting also.

you say the tach is off 1000 rpm, think its flaking out at 6500 and not 5500?

Just throwing some ideas out there for you.

[paanta]

Yeah, I dunno if it's off a thousand RPM @ 5500 RPM. That was just a theory that'd explain why it seems like it's hitting the limiter at 5500. Seems unlikely, though. Never had a tach that was off like that.

I'll give the plugs and wires/boots/whatnot a check tomorrow. The car's in the garage but even that is DAAAAAAAAAAAMN cold right now.

[paanta]

Hell, dude, you're practically local.

[632 Regal]

no kidding! about an hour I'd guess...

Hell, dude, you're practically local.

[paanta]

Today it'll go up to about 5800 rpm before the limiter hits. Definitely starting to think I might want to get a whole DME to swap in...

I got a hand held tach, and it looks the one in the dash is reading spot on.