Definitive Cruise control Thread

[thedguy]

Mine is horrible, I don't use it.  I tried replacing the actuator and cable.  The only time I can use it comfortably is up steep hills.

As soon add I engage it, it pulls enough throttle to get "15mpg" and it instantly tries to gain five miles an hour.  Then completely drops throttle, losses 5mph, and starts again.

It's beating my motor mounts up and just not comfortable.  I chalked it up to being a system built for a bigger engine.

I wonder if it'll improve if I go lighter fly wheel...

Oh well, I don't really need it as much as before.

[DesktopDave]

That's really odd - mine is pretty smooth.  It's not as glass-smooth as it was in an M20, but it's close.  It has a bit of a surge on slight uphill grades or in stiff headwinds.

I'd wonder if the clip is hanging up on the interior of the cruise control housing or something like that.  BMW had a little trouble with the cable sheath too - there was a TSB about cracked adjusters and damaged cables IIRC.

On big hills it's pretty good.  I also noted that on really long steep downgrades, it tends to light up a CEL on occasion.

[meintii]

Bringing this ups from the dead but, VERY good info on here. Thanks guys.

One question though, I just pulled all the cruise stuff out of my 88 325i parts car and got the green plug for the cluster, but there is nothing actually plugged into it. Pulled the whole cruise harness out w/ computer but dont see the male plug that plugs into this.. ideas?

[keflaman]

Bringing this ups from the dead but, VERY good info on here. Thanks guys.

One question though, I just pulled all the cruise stuff out of my 88 325i parts car and got the green plug for the cluster, but there is nothing actually plugged into it. Pulled the whole cruise harness out w/ computer but dont see the male plug that plugs into this.. ideas?

There should be a single, blue/yellow wire enclosed in black (heat shrink?) tubing with a black, two-pin connector that plugs into the green connector; looks like this: http://www.theguestroom.net/car/318cruise/p1010001.jpg

(Pictures courtesy of member "jakeb" in post #57 http://www.theguestroom.net/car/318cruise/)

As mentioned in other posts, I noticed the system operating rather abruptly when starting inclines or coasting down hills. It was embarrassing when another car slowly gained on me only to have my car race ahead as we started up hills. Earlier this week I made a trip to Charlottesville and noticed the cruise control operation had really smoothed out since initial installation. I wonder if the computer has an "adaptive" mode?

[DesktopDave]

I'd be surprised if it's an adaptive system - seems like a simple stepper actuator that constantly attempts to match the set speed.

Do you think it could be the design of the M42 TB vs. the less progressive M20?  Maybe the return spring in the unit is on the way out?  I have also seen two versions of wiring harnesses off the switch - for no obvious reason I could figure out.

[meintii]

Just want to give thanks out to all that have put useful info in this thread! Another successful cruise retro fit here! About the surging on hills.. I just drove 1000 miles to move with my new cruise and that thing stayed pegged right where i set, no surging, no issues at all. All the functions work properly (de/accel, resume, cancel etc).
Thanks again guys for making my road trip more enjoyable!

[DesktopDave]

Nice to hear - glad you found this thread.  I agree 100%, a CC upgrade was one of the best mods I did on my car.  I'd rank it 2nd, only the sport seats were better as far as long-haul comfort goes.

[Gerta318is]

Finally finished mine.  Works amazing!  Between this and cup holders in the car, two of the best mods.

[DesktopDave]

Finally finished mine.  Works amazing!  Between this and cup holders in the car, two of the best mods.

Post the cup holders too!

[Gerta318is]

Dave,  These are from GearSwitch.  Hold on I will post up the link.

https://www.youtube.com/watch?v=CfpsqOAuTSw

The inventor, Ryan Carag, has a 318is as well!  I think this a well thought out product and one that I highly recommend.