Uncontrolled Revving

[SF0059]

I searched for this, but couldn't find anything similar. For reference, I have a 2004 3s 2.3 MT w/113,000.

This weekend, my wife and I took my Mazda 3 from southern VA to NJ. Just outside of DC my car started to jerk in cruise control at 65 mph. After continuing to jerk, I unengaged the clutch at 60 mph and took my foot off the gas. The engine continued to rev back and for between 2500 and 3000 rpm within 5 seconds. I could not get it to stop. Even at a full stop at the gas station the engine continued to rev back and forth. Turning off the car rectified it for about 15 minutes, then the problems started again.

I parked the car in DC and got a rental car to NJ. I decided to drive the Mazda back down to southern VA afterward. After about 100 miles, the same as the last time, the engine began to rev uncontrollably between 2500 & 3000 rpm. The only thing that would fix this for about 15 minutes was turning the car off.

Has anyone had this happen before? The car is not throwing a code and is not missing. When it goes through the revving issue I notice that the car has MUCH less power. I recently changed the spark plugs to Autolite Iridiums and changed the coil the coil boots and springs. Because it is not missing I do not think this is the problem. Any thoughts?

 

[GumbyJarvis]

Check your spark plug wires?

 

[Barkleymut]

Idle control valve, TPS, or vacuum problem are the places to start. Buy me a 12 pack and I will be there and fix it....really.

 

[Colt45ws]

Ignition has nothing to do with it. Have to be something along the lines of what barkelymut is suggesting.

 

[Warstud]

With the vehicle running and the hood open...have someone shut the vehicle off while you listen for a hissing sound from a loose vacuum hose.

 

[SF0059]

I also am leaning toward a vacuum issue. I'll happily buy a 12 pack for an answer! This is almost exactly what I am experiencing, although the video provides no solution...

http://s15.photobucket.com/albums/a392/XCNuse/?action=view&current=c10eaa6e.mp4

 

[Dave Hess]

Didn't the Mazda 3 have problems with the intake manifold ?

 

[SF0059]

Vacuum and intake manifold would yield the same results. Any one have a similar experience?

 

[bdcardinal]

Something either in the fly-by-wire throttle body or the shutter valve on the intake.

Vehicle does not have plug wires or an IAC.

 

[The_Eric]

I too agree that it sounds like a vacuum leak could be the issue. If possible, start pinching closed various vacuum lines while this is happening to try and isolate what's going on/where the problem is.

 

[Barkleymut]

I just watched the video, I would bet a lot of $$ that its a vacuum leak. spray carb cleaner around each vacuum hose connection. When the engine acts differently than that surging you have found your problem.

 

[bdcardinal]

FWIW we have seen a lot of intake manifolds warp on these where the mate to the cylinder head. Since the intake is plastic, there is no fixing it, except for a new intake.

 

[vssjim]

you also may need to have some type of scan data to help to be sure temp sensors are ready correctly as in ambient air temp and coolant temp. If this car has a MAF sensor most of the time vacume leaks make them idle slow not high unless it is an internal air leak like PCV system because outside air not going through MAF will lean it out and make it stumble and idle low and rough.

 

[mechtech2]

Vacuum leaks would also affect idle.
Probably the idle air motor is OK, too.

This is most likely a cruise control thing. The unit or the computer. Maybe power or grounds.

More info, [instead of what state you are in or what car you rented] would be useful.

 

[SF0059]

Happy to give more info!

The idle is fine. No noticeable miss at all. The power on takeoff is slightly less than it used to be and there are occasional stutters on full throttle takeoff. Gas mileage average is off by about 1 mpg.

I recently replaced the spark plugs with Autolite Iridiums and also replaced the coil over boots. This was prior to the problems starting. I made sure that they were correctly gapped and torqued. I'm positive that is not the problem.

Maintainance has always been regular and I only use the best oils, filters, and parts. I knowmthatnI used Autolites instead of NGKs, but it was a matter of availability.

Do you need any more information? Let me know if there are any gaps that need filled in.

Thanks!

 

[OVERKILL]

Sounds like it could be the TPS.

 

[Highline9]

You can spray some carb cleaner around possible vacuum leak areas and see if engine rpm changes. If it changes theres your leak spot.