Can I post a question re wife's car? (none MB!!)

[onefortheroad]

The plugs were changed about over a year ago, so I could change them. I don't know anyone with a diag kit I'm afraid.

I will change the plugs and go from there. I picked up the ones with the four contact points before, are they better than the ones with a single point? If you use a single point do you have to set the gap?

straight out of the box and in , but do check for damage first incase a tip has been flattened.

 

[Capra]

straight out of the box and in , but do check for damage first incase a tip has been flattened.

No, I never have before. Maybe I should have.

 

[Blobcat]

I always used to adjust the gap with a feeler gauge to the correct cap as listed in the manual at the time. Just thrown them in the last few years as they've been right from the off.

 

[Botus]

So a bad coil pack will switch on an MIL light, nothing is on.

didn't on my w221

 

[Capra]

didn't on my w221

Not sure if it makes a difference but, this is on my wife's Toyota Yaris

 

[Botus]

Not sure if it makes a difference but, this is on my wife's Toyota Yaris

yes saw that.... just mentioning mine was lumpy and misfiring (with a failed coil pack) but nothing on the dash

quite surprised 1 cyl on a v8 could have so much impact

 

[onefortheroad]

just a thought , but a miss-firing coil pack should in theory cause cam shaft sensor errors , which should show up on a fault code read .

 

[Botus]

a miss-firing coil pack should in theory cause cam shaft sensor errors , .

why and how

the cam goes round with crank (at 1/2 speed) and if the engine has VVT then the inlet and or exhaust cam timing or valve lift can change ... what's that got to do with one cyl misfiring ?

 

[Wot1]

Cylinder misfire P codes P0300,P0301-P0308 , 0300 is general misfire, 0301-0308 identify the cylinder.

The following is copied from the internet:

For the case of OBDII misfire sensing it is done by watching for small variations in the engine’s instantaneous RPM via a high resolution crankshaft position sensor. Some engines only have a single crank sensor and some have more than one.

As an example Ford used a single “36–1” (35 teeth spaced at 10° each with a missing tooth where the 36th should be) Another is 60–2.

GM has used 2 sensors, for example on the 60° V6 engines a “7x” main signal and a 24x high resolution for misfire sensing and a smoother idle.

Every manufacturer has its own system.

The crank will naturally slow down on the compression strokes and speed up on the power strokes. If the PCM notices that a cylinder fails to speed up on the power stroke it knows that a misfire has occurred.

The baseline for this sensing IE the misfire profile/pattern of each individual cylinder’s teeth on the engine’s crank trigger is learned during DFCO which stands for deceleration fuel cutoff AKA fuel cut.

DFCO happens when the throttle is closed and the car is moving fast enough for the wheels to keep the engine turning at above idle speed. The PCM stops firing the fuel injectors so only air is going through which means than none of the cylinders are firing.