Hi all,

My wife owns a 2003 Mazda 6, 4 cyl, 5 spd. Lately the engine is intermittently racing (up to 3000 or 4000 rpms) when she stops and disengages the clutch (such as at a traffic light). It behaves as if the gas pedal were stuck part way down, but this doesn't seem to be the case. A trip to the dealer found no problems/codes. Any thoughts on possible causes for this?

 

What is the mileage on the car? I would start by removing the throttle body, clean it properly & reinstall it. The T/Body on our cars are known to act up.

 

Disconnect the pedal cable linkage at the throttle body end and hold onto the wire while somebody works the pedal. If it doesn't move freely and smoothly, that's the problem. While you're in that area, check the throttle cable clamp, return spring, and cruise control linkage too.
If that seems OK, the next most likely candidate is a sticking Idle Air Control valve which needs to be cleaned up, followed in turn by collapsed, split, or disconnected vacuum hoses in the throttle body or inlet manifold area.

 

What are you talking about??? The T/Body on these cars are a sealed electronic unit. There are no cables or anything that runs to it. Just an electrical plug. These cars use Throttle By Wire.

 

Sorry, I didn't realize the wired throttle went back that far. In that case the gas pedal has to be mechanically linked to an accelerator pedal position sensor.
Since the car is showing no codes, it leads me to suspect something outside the electrical loops, so the pedal transducer/ linkage and the throttle butterfly actuator are the suspects. Since the PCM has been able to detect (most) throttle position anomalies and throw TPS codes for 10 years or more, I would opt for the pedal side (which is also simpler to work with anyway). As for the interconnect between the wired pedal throttle control and its interface with the cruise control, I pass.

 

OP, just clean the T/Body & see what it does. Let me know if you need further help.

-Sheldon.

 

try cleaning it as sheldon said. then while you have it off. look at all your vacumm line and make sure there are no cracked, loose or broken vac lines.

as sheldon said the TB on the 6 is problematic...especially from 03-05, mostly 03's and the early 04's

also, one thing you can try is simply resetting the ecu. to do this the proper way you would...

1. disconnect the neg. terminal of the battery
2. remove the plug from the TB
3. press the brake pedal for 30 seconds and release
4. plug back in the TB connector
5. re-connect the the neg. battery terminal
6. start car, let idle for 10 minutes
7. turn a/c on full blast, let idle for 10 minutes
8. turn off a/c
9. drive the car around like you would normally.

NOTE: the car is gonna run a lil erradtic from the reset for a lil while. may stall on you once or twice coming to a stop or even after you have already stopped. no worries, this is normal. drive the car around for about a half hour.

if all vacumm lines are good, your problem should be fixed short of the TB actually having an internal issue.

Oldeng.........

these car dont always throw codes for the issues unless there are SOOO SERIOUS and BLANTANT. so you cannot rely on a code to be thrown for every issue you may experience with the 6

 

Thanks for the suggestions everyone!
(the care has 65k miles on it)

 

Looks like Mazda has never heard of Failure Modes, Effects, and Criticality Analysis.
Some of those untrapped snags can have potentially serious repercussions, both from the perspective of safety and in cost of neglected repairs.
What a bugger: we are being used as (expendable and affluent) guinea pigs.

 

Cleaning the throttle body seems to have fixed the problem. Thanks again for the help.