My Cruise Control Died!

[higaran]

I have a mostly-stock '92 Laser Turbo AWD 5-speed. About six months ago, my cruise system went dead. The little orange light on the cruise control column "stick" comes on when I try to set it, but the cruise light in my dash never turns on. The system doesn't "grab" my gas pedal, and seems to have no effect on my engine or my speed.

It's a royal pain in the you-know-what, because I do about 10 hours of highway driving a week and I'm getting nasty foot cramps.

When the problem first occured, I took the car to a local gas-station grease monkey. He checked the obvious stuff and then told me he'd need more time to properly diagnose it.

So then I decided to take it to a more expert mechanic about two hours away that makes a business out of working on exotics - Porsches, Ferarris, BMWs. I'm not a techie myself, but I trust these guys far more than my local Chrysler and Mitsu dealers - they have never misdiagnosed anything on this car before, and have "undone" a lot of botched repairs made by the clowns at my local dealerships, whom I no longer trust at all.

They spent about four hours under the hood testing everything there was to test. In the end, they told me the problem must be my ECU (?) because everything else functions just fine.

Chrysler wants a thousand bucks to for a new ECU, and I can't find an exact replacement wrecker part anywhere - even on eBay. But I did contact a couple of shops that rebuild DSM ECUs. Each shop I've spoken to insists that rebuilding my ECU won't fix the cruise - they say the ECU has no interraction with the cruise.

The other day I pulled my ECU out and examined it - no stinky capacitors, no damage of any kind visible. Everything else on the car operates just fine.

BUT I WANT MY CRUISE BACK!!!! Can anyone help me?

 

[ddavisaf]

Check your VSS, your Reed switch (located inside the instrument cluster), cruise control throttle cable, and the cruise control solenoid.

 

[higaran]

okay:

1. I am, as I said, a non-techie - that's why I spend about $5,000 bucks a year paying mechanics to do anything more advanced than changing my oil or rotating my tires. When I start monkeying around under the hood myself, I generally wind up taking the pieces to a professional. Where exactly are these parts located? What (and how much) stuff am I gonna have to remove to get at it? And once I've found the parts, how exactly do you check them? Just make sure the connections are OK? As for the VSS, shouldn't this be the same one used by my speedo? 'Cuz it's working fine.

2. Wouldn't these be the first things an experienced mechanic with eight gigabytes of DSM-specific info would check? I mean, after four hours (and $350) worth of tinkering, I feel reasonably sure that the electromechanical stuff is functioning as it should.

I guess what I want to know is this: Is it possible that the ECU does have any interraction with my cruise system? If so, could it, in fact, be responsible? Or is he out to lunch. I don't want to spend $400 rebuilding my ECU to find out that it's no different than before.

Your thoughts?

 

[badas93tsi]

I have all the necessary underhood parts for a 93 awd. They work perfect, I just took them off for the extra room, and used a 1.8 non-cruise cable. Let me know man, I havent listed this stuff yet.

 

[ddavisaf]

okay:

1. I am, as I said, a non-techie - that's why I spend about $5,000 bucks a year paying mechanics to do anything more advanced than changing my oil or rotating my tires. When I start monkeying around under the hood myself, I generally wind up taking the pieces to a professional. Where exactly are these parts located? What (and how much) stuff am I gonna have to remove to get at it? And once I've found the parts, how exactly do you check them? Just make sure the connections are OK? As for the VSS, shouldn't this be the same one used by my speedo? 'Cuz it's working fine.

2. Wouldn't these be the first things an experienced mechanic with eight gigabytes of DSM-specific info would check? I mean, after four hours (and $350) worth of tinkering, I feel reasonably sure that the electromechanical stuff is functioning as it should.

I guess what I want to know is this: Is it possible that the ECU does have any interraction with my cruise system? If so, could it, in fact, be responsible? Or is he out to lunch. I don't want to spend $400 rebuilding my ECU to find out that it's no different than before.

Your thoughts?

I've schooled a couple "master technicians" in the world of DSM's, so.. it's possible they didn't know, or they did and checked everything. No, I cannot see your ECU being the cause of your problem. Simply because the cruise control is an electromechanical system. Meaning, it relies on electricity to activate the solenoid, which in turn sets the cable at a certain place.
VSS - Vehicle Speed Sensor, on the top of the transmission
Reed switch - switch that operates the speedometer located inside the intsrument cluster
Yes, both of these affect the speedometer. However, if the cruise control is not setting as it should, it may be due to a problem with either two switches. I have a couple more ideas, but I don't want to throw them up yet until I get a chance to see if I may be right.
When the CC was working and you applied the brakes was the CC automatically disengaged? If so, the switch that controls that operation may be bad as well.

 

[kscott]

The cruise isn't controlled by the ECU. It's got its own separate little
electronics box that's located somewhere above the fuse box,
buried inside the instrument panel.

The first thing I'd look at would be the switches for both the
clutch pedal and brake pedal.

 

[BoostActionBob]

you may also want to check to see if the sensor that connects to the "crusie control brain" under the hood is plugged in. i was messing with some things under my hood and unpluged it and had the exact same problem as you. pluged it back in and it works just dandy.

my .02

 

[higaran]

Thanks to all for replying:

You say there's another electronics box for the cruise system? I wonder if that's what my guy was talking about then (although I could have sworn he said "ECU"). Does anyone know if this box has an "official" part name? Perhaps I've been getting price quotes for the wrong thing from Chrysler.

Knowing these mechanics as well as I do, I expect they have already checked the VSS, reed switch, and the disengage switches for the clutch and brake pedal. But it probably couldn't hurt to ask and make sure. I will maybe give them a call to find out more.

Thanks!

 

[higaran]

you may also want to check to see if the sensor that connects to the "crusie control brain" under the hood is plugged in. i was messing with some things under my hood and unpluged it and had the exact same problem as you. pluged it back in and it works just dandy.

Yes, that happened to me a couple of years ago. Just after I bought the car, the cruise stopped working. I drove without it for a few weeks, but one day when I was monkeying around with something else under the hood, I found this connector just dangling there. It only took me about five seconds to figure out where it was supposed to go, and I had my cruise back. The cheapest DIY repair job I've ever done!

If only it were that easy... this time I'm pretty sure it's something else.

Thanks anyway - much appreciated.

 

[TURFNNSURF]

Check your vacuum lines to the cruise control unit under the hood located on the firewall. Trace the line to the Vac canister on the drivers side wheel hump. My cruise control stopped working on me on the highway, just like you described. I found the original Vac line had hardened and cracked from 14 years of engine heat. I replaced the vac line and everything was good as new.

 

[higaran]

Thanks - will have a look at it also.