Whenever i am on interstate and i hit a bump like going over a bridge or something my cruise turns off. I have my car lowered with the tein basics, i dont know if that would have anything to do with it. anyone else have a problem like this? if so what fixes it?

Maybe it has to do with it being lowered, thus being beaten more by bumps when driving fast, that the ABS system kicks in ever so slightly forcing the cruise to cut off. Never heard of such a thing though.

Do you have any other modifications done to your engine or is your check engine light on? Any fluctuation in idle will cause the cruise to kick off for safety reasons. Not too sure about going over bumps

Weird... If the springs are the only mod I would be taking that right to the dealer.. Did the dealer reflash your ECU for the '04 knock problem? maybe they boned it!? I've seen dealers do dumber things...

Any fluctuation in idle will cause the cruise to kick off for safety reasons.Idle and cruise control ON would seem to be mutually exclusive conditions, so I can't imagine how any fluctuation in idle could have any affect on shutting off cruise control.

According to this document (http://www.autocds.ru/2004%20STI/08.%20MECHANISM%20AND%20FUNCTION/63.%20CRUISE%20CONTROL%20SYSTEM%20(Sti)/01.%20Cruise%20Control.pdf), when any of the following conditions is met, the cruise control is cancelled.
(1) Stop light switch ON (brake pedal depressed)
(2) Brake switch OFF (brake pedal depressed)
(3) Clutch switch OFF (clutch pedal depressed)
(4) Neutral switch ON (shift lever moved to neutral)
(5) CANCEL switch ON (command switch pulled)
(6) Ignition switch OFF
(7) MAIN switch OFF
(8) Transmission gear in 1st or reverse.
(9) Actual vehicle speed drops below 32 km/h (20 MPH)
(10) Abnormality in the system is detected.

So I would guess that maybe one of those switches mentioned is firing (or cuts out) erroneously when you hit a big bump.

It is a safety control. If the idle flucutates due to an "abnormality" in the system, it will cause it to shut down. For instance, if the idle were to suddenly "spike" due to a mass air flow malfunction, it will cause it to shut down. This way the vehicle does not "lurch" out of control.

Here is an excerpt from the "diagnostic" manual. It states that if there is a "variation in engine speed", it will cancel the cruise. This variation does not necessarily cause a DTC though.


CRUISE CONTROL SYSTEM (DIAGNOSTICS)
22 Vehicle speed variation is abnormal.
Abnormality of vehicle speed variation is detected. <Ref. to CC(STi)-27, DTC

22 AND 32 VEHICLE SPEED SENSOR, Diagnostic Procedure with DTC.>

23 Engine-related sensor is abnormal.
Abnormality related to engine is detected. <Ref. to EN(STi)-2, Basic
Diagnostic Procedure.> DTC Item Contents of diagnosis Reference

I took my car to my local dealer today and they said the fact that i had it lowered there was nothing they could do. They said the harshness of the ride is moving the brake when i hit a bump therefore kicking the cruise off. I think this sucks because my car rides good considering the lower ride. I guess i will just have to deal with it :(

That's amazing they could just look at your car and know which switch was triggering the cruise control cancel. But, for all I know, this could be a common problem with the STi - I don't read the Brakes and Suspension forum. Maybe you should check in with those folks to hear what they say.

My 04 FXT does the SAME THING! We drove to from CT to MS back before the holidays, and the cruise was acting up the entire way there and back. It would just randomly turn off. Very weird. I took it into the dealer, and they said they couldn't duplicate the problem, but the service manager told me that he checked all the possible connections that could be loose himself, and that they were all fine. He also said that he drove it, and that the cruise control worked fine. :confused:

I took my car to my local dealer... They said the harshness of the ride is moving the brake when i hit a bump therefore kicking the cruise :(

That's just about what I suspected, either the brake or clutch switch being activated by the bump. You can adjust those switches to be a little less touchy and it may solve the problem.

My 04 FXT does the SAME THING! We drove to from CT to MS back before the holidays, and the cruise was acting up the entire way there and back. It would just randomly turn off. Very weird. I took it into the dealer, and they said they couldn't duplicate the problem, but the service manager told me that he checked all the possible connections that could be loose himself, and that they were all fine. He also said that he drove it, and that the cruise control worked fine. :confused:

Same problem on my 04 FXT as well - but I know why now after another thread on this subject a couple months ago, it's the shift lever moving slightly & probably engaging the neurtal switch. If it kicks off I can nudge the shift lever up a bit & it'll work fine again. Hard to duplicate for the dealer in my case because it's more likely after you've been on the road for a while & is also speed related - won't do it below about 75 mph.