Ford Fiesta, t-reg, J4 engine (1.3 with MAP sensor)Archived Message
Posted by Ian Staples on March 31, 2008, 8:40 pm
Hi there. This vehicle suddenly developed an erratic speedo (fluctating 5 or 10 mph and a few times indicating zero) and holding back and misfiring, more so under load, but is fine under gentle throttle.
Before anyone replies with years old common knowledge of setting up the throttle or adjusting the TPS or ISC valve, etc., etc., its not that. Theres no idle hangup or stalling (other than pilot error, lol). Its fine when revved hard stationary and moving the wiring has no effect.
Faults present were No2 cylinder misfire detected and VSS intermittant no signal. Replaced VSS with known working unit, no different. Checked gearbox internal speedo drive, no problems. On the road ECU live data has no VSS signal all the time even when speedo works. There is no speedo cable so considering dash fault or broken connection.
Im also gonna replace ignition leads and coil with known working just to rule it out, but i dont think its that as its only happening when the speedo plays up.
Ive searched the archives, nothing matching the symptoms or the fix has been things ive already tried.