Limp Home Mode? w/videos

[Lof8]

I'm still trying to get my S50 swap running perfectly. I made a lot of progress when I found I deleted my charcoal canister incorrectly. The car now idles fine.

I'm hitting what seems to be a rev limiter at 3.5k rpms. I think my dme may be going into a "limp home mode" As the car will rev to redline for the first 5 minutes after disconnecting the battery for a while.

Here is a video of the rev limiter.

http://www.youtube.com/watch?v=7rzH0v51hEk

No CELs

I have disconnected the battery and will post another video in about 15 minutes

[Lof8]

My suspicion of a limp home mode may be confirmed. I disconnected the battery for 15 minutes, came back and made the following video:

http://www.youtube.com/watch?v=pi5QsKdpJq0

Now, what the hell is causing this?

still no CEL.:(

[Spaz]

Well there must be something putting the car into limp mode, a sensor failing after heating up?

No CEL's Ever pop up?

-Cam

[Lof8]

No CELs at all since fixing my charcoal canister problem.

[Lof8]

With some searching, I have found that my dme may not be getting a vehicle speed signal.
Anyone care to chime in here?

[bwh13]

Have you done the 'gas pedal stomp' test to see if anything comes up that way? Sometimes the fault code doesn't activate the CEL...

[Lof8]

Have you done the 'gas pedal stomp' test to see if anything comes up that way? Sometimes the fault code doesn't activate the CEL...

yes, I did this. still no codes.

I think that my problem here is no speed signal to my dme.

Has anyone fixed this by connecting e30 pin 14 to e36 pin 9?

Jogfrogjog has suggested this:
"I pulled the speed signal from my gauge cluster to my harness adapter and that took care of it... if you look on the back of your cluster, there are three prongs on the green port, I think any one of the three would work and just run a wire for the prong to the speed signal pin... "

It would be easier to just connect a couple of wires in the adapter if that will solve the problem.

[Lof8]

this has also been posted as a suggestion:
"You need to connect E30 pin 14 to E36 pin 14. This is the road speed signal into the DME. Without this signal, you will not reach maximum RPM."

[87e30]

this has also been posted as a suggestion:
"You need to connect E30 pin 14 to E36 pin 14. This is the road speed signal into the DME. Without this signal, you will not reach maximum RPM."

Hmmm. Mine seems to be cutting at 5000rpm but I'm having all sorts of other problems as well so I'll keep this in mind if fixing other problems doesn't work.

[Lof8]

there are three speed signals.



- one road speed signal comes from the diff and goes to the speedometer. dont touch that.

- one ROAD SPEED signal that goes from the speedo, through the c101, to the ecu. its the same signal that goes to the speedometer, but is safer to mess with it at the c101.

- one ENGINE SPEED signal that goes from the ecu, through the c101, to the tachometer.



if the ENGINE SPEED signal is not hooked up, your tachometer will not work.



if the ROAD SPEED signal is not hooked up, vanos will not actuate, ignition/fuel ratio will be changed, your idle will not kick up to 1100 when you are rolling down the street. in essence, your car thinks you are sitting at a stop light reving the engine, trying to show off to the girls sitting at the park bench. it will not impress them, or the g-tech.

cheers, jason

for the road speed signal.......



ROAD SPEED signal comes from the cluster to the c101 on the e30 chassis:

- pin 14 blk/wht wire (for 88+ "i" cars)

- pin 14 blu/yel wire (for late m3's)

- does not exist at the c101 for most "e" cars. you will need to tap into it between the obc and cluster, drag wire into engine bay, patch to x20.



ROAD SPEED signal goes to the m50 ecu from the x20 connector:

- pin 14 blk/wht wire (for the 93-95 e36 m50tu.)

- pin 14 brn/red wire (for the 91-92 e34 m50nv.)



cheers, jason



EDIT: most people (including here on this board) want to just copy some cheesy / almost correct pin diagram off the internet. i have not seen anyone address this issue for older cars. so, i bet that there are A LOT of cars running this way.

[Lof8]

well, I pulled my gauge cluster out yesterday and found a vehicle speed signal wire coming off the the speedometer. It was routed over to the dme and had been connected to the to the old m20 wiring harness near the dme. I rerouted it through the firewall on the drivers side and will be attaching it to x20 pin 14.

Hopefully this will:
-eliminate my dme going into limp mode
-raise the idle to 1100 when the car is rolling
-give me some more ponies because vanos will be working??

[325issguy]

I think your getting there.... Not sure what diff your running but you definately should pick up some power. It seems like my m52 runs through the gears faster than that.

[Lof8]

Vehicle Speed Signal was the final piece of the puzzle. The car screams now. Thanks for the help!!!!!!!!!!! Fuck Yeah!!!!!!!!!!!!!!!

[lennon]

AWESOME! i am glad to hear that.

[Gray S.]

you dont perhaps have a picture of the wire on the back of cluster do you? I'm hunting for this on my 318is (which doesn't have cruise control). I think I may just end up buying the green plug for cruise and wrapping a wire around one of the prongs and hoping for a speed signal.