Cal Club Autocross Forums

Strange thing happened with my car last night. It tried to kill me. Driving home late on Ortega Hwy, about 10 miles from home acts like wide open throttle, able to control for a while with brakes, but when started downhill, began to fade and jut managed to get off to side and shut down. Tried to cool down, but too scary on the steepest and tightest part, so gave up. This is a 2001 Mazda Tribute, V6. So just a cable to the throttle body. Simple. In the rain on the side of the road tried trouble shooting. When I start it, immediately goes to 6k rpm. Checked cable, return spring, and took off hose and checked throttle is closed. No cruise control, no obvious hose leaks, not that much excess plumbing like newer cars. Don't see how it can do this. Finally got towed home, not sure where to look for problem. What am I missing? Guessing maybe vacuum leak, just haven't found it yet. Would help if I had a garage and it would stop raining......
Post here or 949 - two four four - 59 three two

Yep, looks like a bad hose. Of course a unique shape, different size on each end. Working on a MickeyMouse fix till I can hopefully get the correct part.

I was going to say vacuum leak.

oh, that's bad Rick. But yes, It sounds like a vacuum leak. I am going out on a limb here to say this is a MAP sensor car because MAF cars don't do this. My Omnis, yes I owned more than one- didn't learn the first time..., each had this problem when they had a vacuum leak. Another possibility, but less likely, is the idle air speed control motor going faulty and opening when it's really thinking it's closing the idle port in the throttle body.

A good temp fix for a formed hose that you cant find readily is to cut a thin piece of runner and affix it to the opening with Shoe Goo. then wrap with electrical tape or shrink wrap if you have some the right size.

Earl Merz wrote:oh, that's bad Rick. But yes, It sounds like a vacuum leak. I am going out on a limb here to say this is a MAP sensor car because MAF cars don't do this. My Omnis, yes I owned more than one- didn't learn the first time..., each had this problem when they had a vacuum leak. Another possibility, but less likely, is the idle air speed control motor going faulty and opening when it's really thinking it's closing the idle port in the throttle body.

A good temp fix for a formed hose that you cant find readily is to cut a thin piece of runner and affix it to the opening with Shoe Goo. then wrap with electrical tape or shrink wrap if you have some the right size.

The hose was definitely bad and I did fix sort of like you recommended, piece of plastic tubing that just fit inside, heated to bend to the correct angle, then electrical tape. Unfortunately, didn't solve the problem. Actually it's a MAF on this car. Have to look for the idle motor you mention.

I did a quick search and the two most common suspects were a vacuum leak and the Idle Air Control(IAC) Valve. I'd inspect all the hoses you can find and replace any that could even suggest a leak. If it still acts up, make sure to clean the throttle body and the Idle circuit before trying a new IAC. It sounds weird, but if you have a 2-3' length of vacuum hose, hold one end near your ear canal and use the other end to trace the engines vacuum hose routing for increased airflow. If I was closer I'd stop by and try to help you find it.

Earl Merz wrote:I did a quick search and the two most common suspects were a vacuum leak and the Idle Air Control(IAC) Valve. I'd inspect all the hoses you can find and replace any that could even suggest a leak. If it still acts up, make sure to clean the throttle body and the Idle circuit before trying a new IAC. It sounds weird, but if you have a 2-3' length of vacuum hose, hold one end near your ear canal and use the other end to trace the engines vacuum hose routing for increased airflow. If I was closer I'd stop by and try to help you find it.

Thanks Earl, I'll look for the IAC on Saturday. Not sure I'd be able to hear anything with it "idling" at nearly 6000rpm.
Had to rent a car to go to work today and have for the weekend if needed.

Earl Merz wrote:the Idle Air Control(IAC) Valve.

Maybe. Looked at the old one, appeared to be stuck partially open. Cleaned, but didn't really seem to make a difference. Jammed the inlet side with a paper towel to force it closed and plug it. Made a big difference, under 2k rpm instead of 6k. Got a new one, started and went to about 2.2k rpm, then started slowing down to about 1.5k, but then started back up to 6k, so turned it off. So not sure now. One of the online sources (where it was causing low/rough idle) said that after replacing it needs to idle several minutes for the computer to calibrate. But I'm not willing to let it "idle" at 6k. Not sure what's next, ran out of daylight to troubleshoot more.

Thanks to Mike Flanigan, who stopped by Monday morning with fresh eyes and some expert mechanic knowledge, he identified the issue pretty quickly as a throttle cable problem. I guess I dismissed it pretty early since the throttle return spring seemed strong and the less than ideal conditions when I looked at the throttle itself had me think it was fully closing. No dealers have the replacement in stock and want a ridiculous price, so I ended up taking it off and used a cable lube and cleaner spray to clean it out. Went from hard to move in the sleeve to sliding through like melted butter. Life is good and little money was spent.

Happy to help!