peejay

I've never heard of this happening on *any* car.

I'm sitting at a light. All of a sudden the redline buzzer buzzes momentarily, and the engine starts revving up all by itself. I kill the ignition just as the needle sweeps past redline and the buzzer goes off again.

What the hell?

I start it up again. Idles rock steady at 800 like normal, for about a second, then the engine makes for redline again.

Shut it off again. What the hell?

Light turns green. Start it up, put it gear, accelerate (without touching the throttle, mind you) into the parking lot at the light, kill ignition, coast into a parking space.

What the hell?

Pull the air cleaner lid off. Yep, throttle blades are shut. Peering under the air cleaner, the secondaries linkage seems to be hooked up okay, and it's such a production to remove the air cleaner (what with the vacuum hoses, air pump hoses, and fuel pressure regulator bolted to its side) that I leave it on and think. Checked the vacuum cap covering up the hose nipple over the exhaust manifold. Yep, still intact. (Got tired of the hose failing) Then I chide myself - it can't be a vacuum leak, it runs just fine, it's just possessed.

Hmm. I know some of the electricals are starting to fail. Last week I finally unplugged the coolant level light module. The light would come on and off at random, the sensor wire was physically disconnected and grounded. I remember my rule: Fix something and something else will break, there's always ONE thing wrong.

I start the engine. It performs its now-customary idle for a second and then reach for redline. Shut it off.

By now the people at the auto parts store are looking at me kinda funny. I dunno whether they expect a sale from me or will prevent me from entering the building.

Well, let's think. SOMETHING is pulling the throttle open. The carb linkage is okay. The hot start assist does NOT have that kind of motion - it can only raise revs to maybe 1500rpm max.

Cruise control? Normally I leave the cruise armed and just hit the stalk buttons when I want cruise, since the button is pretty hard to access. I hit the button to turn it off, and start the engine.

Rock solid 800rpm idle.

Hit the button again. Revs skyrocket. Hit button again. Drops to idle.

Curse, swear, go around to the other side of the car, unplug the cruise control. Restart engine, play with button, cruise control now has no control of the engine.

Dammit, I *like* having cruise control. This is only my second car to have it and I enjoy using it. But at least my car isn't possessed anymore.


- Pete (Philosophically speaking, now I don't have to hook it up to the Holley or whatever carb(s) I decide to go with)

mazdaverx713b

iTrader: (91)

do you think something got by the aircleaner and wedged itself in the carb causing the throttle to stick open. i had that happen to me. i had a piece of gum in my carb. i bought an 85 and drove it home. when i finally got home, i took off the aircleaner assy. no aircleaner element present. i carefully inspected everything. found the gum sticking in there and causing the rpm massacare. i fished it out and replaced the aircleaner and had no problems. perhaps you have something wedged in the carb?

gsl-se addict

iTrader: (3)

Sounds like your cruise control is possessed. It may be the controller module under the drivers storage bin, or possibly the switch itself. I would lean toward the cruise control module though.

peejay

I would also, however the liklihood of getting known good parts cheaply approaches zero. Never trust used electronics.

What makes me think it's wiring or module instead of switch is that the engine would rev with the clutch and/or brake depressed, both of these *should* disable cruise. So it's not, say, something worked loose in the combination switch and shorting the "set" button (which will accelerate the car if you hold it down).

Jeez... my car is turning into an FC with these elecrical failures. First the headlight contacts in the combi switch started dying, that was fixed easily. Then the coolant level light problem - finally fixed that last week. Last month the trailing ignitor *seemed* to start dying - tach would jump around under load when cold and accelerating. That kinda self-repaired before I could confirm, but that would make it the second ignitor in 15k if that's the case. (I have only one spare left) And now I'm cruiseless in Cleveland.

I sure hope the emissions controls are working okay - I need to throw a cat on the car and E-check it soon.

smnc

I have a spare control box if you need one... PM me if you're interested...

cdrad51

Yeap, as I was reading your post I was thinking, I bet is the cruise control. I know because once made the mistake of putting the engine in neutral without using the clutch while using the cruise control and of course as the car lost speed the mechanism increased rpm to try speed up, and kept doing so as the rpms didn't result in increased speed. It took me a few seconds but then realized what it was, pushed the clutch in and the cruise control of course disconnected. So you have narrowed down the general area that is failing.

Hope this reference helps

http://www.wankel.net/~krwright/file...Electrical.pdf

page 47

Siraniko

iTrader: (13)

hey pee-jay
need a mechanic?? j/k get a 12-pack and think it over. you will figure it....

smnc

It actually beats my wierdest failure.

I was sitting at a stoplight and *BOOM*
*hissss.......*

THIS happened to my upper rad hose...

Anex 570

Alright, i'll admit, thats impressive.

LongDuck

There are also 2 vacuum solenoids attached to the passenger side of the firewall that are used when you press the 'resume' and 'accelerate' buttons on your cruise control system. If these vacuum solenoids go out, they could be allowing additional pressure into the speed-sensing diaphragm making the cruise control think that your car is decelerating.

Check these via the instructions in the FSM, and you may not have an electrical problem with the control box under the driver's bin, or the stalk controls. Good luck, that is a weird problem,

peejay

Yah, have been poring over the FSM about this.

But - remember Rule #2: As soon as a problem is fixed, something else will break. (Rule #1 is: If it ain't broke, wrenches only make it worse)

I think I'll leave it alone. Now that I'm working again, my driving has shifted back from "cruise at 70mph" to "drive at 85 until there's traffic, get through traffic, drive 85 until the next traffic clump" so the cruise isn't as necessary as it was before.

But it's nice to have when cruising through the park...

riofrio

That's weird... the same exact thing happened to me, only in the highway (I hit the button to turn it on only when i want to use it). It was working just fine for a while, and all of a sudden it just wanted to accelerate constantly. It kept happening every time I tried after that (just being curious), then I forgot about it for a while... and yesterday I tried it again and it worked fine.
I don't get it!