Plastic inlet manifolds have been known to leak around their seams, but would be very rare on a non turbo.
 
Just a linked question if I may? How does the obd detect a misfire? Does it only detect probs with electrical side or can it detect injector and fuel starve problems and still give a fault code?
Thanks...
 
andyfreelandy said:
Just a linked question if I may? How does the obd detect a misfire? Does it only detect probs with electrical side or can it detect injector and fuel starve problems and still give a fault code?
Thanks...
Click to expand...
I use the Delphi e150 with laptop it will tell you the pressure that it is running at
 
My scanner is very basic... I will remove the inlet manifauld and inspect for any leaks...

I know it's not coils and or plugs because they were replaced recently...

I will try to test fuel pressure as well...
 
andyfreelandy said:
How does the obd detect a misfire? Does it only detect probs with electrical side or can it detect injector and fuel starve problems and still give a fault code?
Click to expand...

The ECU is capable of detecting timing variations via the pulses from the crank position sensor. The ECU also knows the position of the crankshaft in its rotation, so if the pulses it's monitoring change in frequency around a particular cylinder, it knows there's a misfire in that cylinder. The ECU also monitors how much current is being consumed by the coils and injectors, so will flag if those are open or short circuit.

Misfires without coil or injector errors are down to the HT side of ignition, or fuel / air issues.
 
Thanks. A mate is bringing a 1.8 with a misfire for me to wave a magic wand at!! Just wanted to know what the codes are actually telling me. The clue is in his statement 'changed the plugs and now it's worse'!!
 
andyfreelandy said:
Thanks. A mate is bringing a 1.8 with a misfire for me to wave a magic wand at!! Just wanted to know what the codes are actually telling me. The clue is in his statement 'changed the plugs and now it's worse'!!
Click to expand...
I’m going to guess Poor spark due to failing coil packs and plugs that aren’t correctly gapped
 
Yes, or the plug contact springs have gone floppy! Are they really that sensitive to plug gap? My old Ford is fine as long as the gap is somewhere between a hair and a file's width! It also runs on paraffin!! Manyany years ago my Dad 'tidyed up' and put odd drops of 'petrol' into our 100e. Very sooty exhaust confirmed that he had actually poured in a couple of galls of paraffin!! Got us home though. Plugs resembled an old sooty chimney. Happy days....
 
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andyfreelandy said:
Are they really that sensitive to plug gap?
Click to expand...
Yes, and plug type too. The K series has a 10.5 to 1 compression ratio, so needs a good hot spark to fire the mixture correctly. The plug gap should be bang on 1mm, and ideally the plugs should be of the platinum type, which the OE plugs were of course.
 
Ha, coincidental I just got a set of plugs to fit as the old ones have nearly done 100,000km - NGK PFR6N-11.
 
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