I've been getting this same misfire since I bought the car over a year ago. Seems to happen at load and it's only usually the 1 misfire that happens.
I've changed the ignition coil, spark plugs and coolant sensor. I've ran a bottle of RedEx. Still misfires.
I've begun checking the Lexia logs.
1000Mb manifold pressure? Is that 1000 mega bar? Doesn't sound right to me! What do you guys get for usual manifold pressure?
Last time I checked the Lexia log it was 890Mb pressure and it's always around that kind of height.
Makes sense that it will be 1000 millibar. Must just be an error in the Lexia program that it displays as Mb.
I took a real time log of manifold pressure, O2 sensors, engine and vehicle speed this morning while dropping the Mrs at work. The manifold pressure reading above doesn't seem erroneous. I'm thinking now that I may be looking in the wrong area for solving this.
So far I've fitted a brand new ignition coil and spark plugs and a brand new coolant sensor so I'm going to cross them off the list.
I was thinking that there could be a vacuum leak but the manifold sensor readings don't indicate that.
Other things that control ignition timing are the crank sensor, cam sensor, throttle sensor and O2 sensors. I might start looking at replacing those sensors.
Have you changed the HT leads, the symptoms you describe would suggest a too wide spark gap at the plugs or a breakdown of an HT lead, check the leads or try reducing the plug gap by a thou or two, but no more.
Man is, by nature, a lazy beast, he does not need twice encouraging to do nothing.
The ignition coil on this engine (EW10 J4, 2 litre petrol, 138Bhp) sits directly on the spark plugs so no HT leads.
Will maybe try another brand of spark plugs. Currently got Champion REC9YCL plugs which are one of the 3 types listed on Autodata for this car/engine.
addo: Here's my sensor data. Does the manifold pressure look funny then?
There are some odd MAP sensor readings (note especially the 17-13 MPH deceleration about 75% down the page), however it could be an issue with the supply constant voltage (5V IIRC).
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addo wrote:In a healthy N/A petrol engine you should be pulling 16+ inches of Hg. That's 550-odd millibar.
IIRC, 21 inches HG is the maximum theoretical manifold pressure at idle. I once got my old Triumph Vitesse idling at 21 and it ran like a dream. 17 inHg is more normal.
addo wrote:There are some odd MAP sensor readings (note especially the 17-13 MPH deceleration about 75% down the page), however it could be an issue with the supply constant voltage (5V IIRC).
Cheers addo. I'll clean up the plug with some contact cleaner and check for oil on the sensor and if that doesn't work I'll get another MAP sensor.
To be sure isn`t O2 sensor faulty unplug it and the car will work on a emergency map without misfires. If the problem goes away replace O2 sensor.
Dont worry if Antipolution faulty will came up on screen. You can delete it after doing this test.
