Problem fixed, but what caused it?
Discussion
Hi,
Car is a 2004 Mazda 6, 1.8 Petrol. 98K, Fsh. No EML / Fault code showing.
The revs would not drop below 1500 / 2000 during driving, so when at the lights in neutral the car would sit there idling at 1.5k then after a second drop to 1k rpm. This had been going on for a while, and when I drove along then dipped the clutch to coast, the revs stayed high. Sitting and revving the car dropped the revs down from 5k to 2k quickly , then from 2k to 1k after several seconds.
After lubricating the entire throttle assembly, cleaning out the throttle body and checking for leaks I did a bit of reading, apparently a battery disconnect for a half hour might fix it, so that's what I did and that's what it did. Car is fine and dandy now. Behaves perfectly and no over revving issues.
Could it have been down to bad fuel? and the disconnect forced the ECU to re learn?. The car is a bit of a shed so I filled it up at a local indy garage (applegreen) last couple of times, but most recently it was Tesco, and my partner says she noticed the problem about a month or so ago (which ties in with the cheap fill up).
Did the ECU compensate for lower octane or crap fuel and then throw up the issue?.
If it is fuel then it serves me right for being a cheapskate and hopefully there's no further problems as a result. I know supermarket fuel has it's critics, but the stuff I put in was even cheaper than that. From now on, if it does sound like it was fuel, I'll no longer be a tightwad. Pinkie promise.
Car is a 2004 Mazda 6, 1.8 Petrol. 98K, Fsh. No EML / Fault code showing.
The revs would not drop below 1500 / 2000 during driving, so when at the lights in neutral the car would sit there idling at 1.5k then after a second drop to 1k rpm. This had been going on for a while, and when I drove along then dipped the clutch to coast, the revs stayed high. Sitting and revving the car dropped the revs down from 5k to 2k quickly , then from 2k to 1k after several seconds.
After lubricating the entire throttle assembly, cleaning out the throttle body and checking for leaks I did a bit of reading, apparently a battery disconnect for a half hour might fix it, so that's what I did and that's what it did. Car is fine and dandy now. Behaves perfectly and no over revving issues.
Could it have been down to bad fuel? and the disconnect forced the ECU to re learn?. The car is a bit of a shed so I filled it up at a local indy garage (applegreen) last couple of times, but most recently it was Tesco, and my partner says she noticed the problem about a month or so ago (which ties in with the cheap fill up).
Did the ECU compensate for lower octane or crap fuel and then throw up the issue?.
If it is fuel then it serves me right for being a cheapskate and hopefully there's no further problems as a result. I know supermarket fuel has it's critics, but the stuff I put in was even cheaper than that. From now on, if it does sound like it was fuel, I'll no longer be a tightwad. Pinkie promise.
Anything that upset the ECU could cause that - might be a wiring fault, dirty sensor, or maybe a misfire from dodgy fuel triggering a fault condition. It's quite possible that the initial problem had relatively mild symptoms from the driver's point of view but it was enough to put the ECU into a 'limp home' mode which is what you noticed. If the original problem is still present, the ECU will probably notice it eventually and pull the same trick again.
Hi,
Thanks for the reply. I'm going to fill it tomorrow anyway, some of the old cheap stuff is probably in the tank mixed in with the other Tesco, so I'll just chuck a full tank of Shell's finest in and hopr it doesn't resurface.
There was no EML code or light though which I thought strange.
Thanks for the reply. I'm going to fill it tomorrow anyway, some of the old cheap stuff is probably in the tank mixed in with the other Tesco, so I'll just chuck a full tank of Shell's finest in and hopr it doesn't resurface.
There was no EML code or light though which I thought strange.
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