The forum monitor (for the want of a description) asked if I really wanted to reply to an old post. Reading the replies makes me think I have relevant contribution to give.
That said, I also noted the thread "What MPG do you get?"; this is also relevant.
So the car (Jazz 2012 5dr Hatchback 1.4 I-Vtech ES L13Z1, 124000 miles) has been running OK and over the last few years I have been servicing it myself, including getting right underneath to check the items in the Honda check list. So far so good. During the early phases of this new pastime, I discovered that the garage (I assume) removed and discarded the front clips on the plastic splash shield below the engine - only to realise after replacing them, they are a pig to release. Perhaps there's a special tool...? A screwdriver does not work...
Anyway, then the dreaded service item #9 popped up - the tappets; Check and adjust same...
I note from the other replies comments like "never been adjusted; no problem" and I wonder how anyone would know without checking?
And yes, its a hell of a job to get to them - especially as the Haynes for up to 2010 is more or less irrelevant. But I got there - and there they all were - all sixteen of them aaagh...
The truth is, you must not make a mistake with tappets. And there is no guarantee that you will hear a rattly one either. So this has to be done right...
I have set tappets on anything that "tapped" from my early teens and would jump in where angels feared to tread. My (much) older self would probable now say to my younger self "leave it, don't touch it; this is how you do it but don't...". I am old and worried and crotchety now, so a younger self would just ignore me and do it when I'm not looking...
So I set to and what an awkward job... I had to bend the feelers to get them in place, and I note that the Honda intake valve gap is 9 thou +/- 0.8 thou - I would say that's unrealistic using a screwdriver and feeler gauges. So I considered a tool that would help...
No diagrams - sorry - but how about a cranked screwdriver pivoting in a calibrated circular dial and all supported by brackets that screw onto the rocker cover screw holes. As we know the pitch of tappet adjuster screw, it's possible to mark a circumferential distance around the dial such that beginning with the adjuster snug with zero gap, by turning the cranked end of the screw driver we know the gap must be the calculated amount. There is almost no need to even check it. A screw rotated a specific amount will move (create a tappet gap) a guaranteed amount. Of course the locking nut may move the screw, so I suggest mounting a dial micrometer on top of this lot and manually move the tappet to check the gapping.
So anyway, my Jazz had been looked after by Honda since 2012 and I was shocked how wide the gapping was. It was way out although I have to say I didn't check how far.
I checked the plugs too. One was noticeably wide and the others noticeably small. There was no obvious erosion, so I think Honda had chucked them in straight from the box without checking.
When I first bought the car, there was a lot of brake drag and mileage around 40-45mpg running around (I'm retired); and 55mpg on a run.
I spent a few years learning to strip the callipers an finally made them operate, what I call, properly...
About a year ago I went from Camberley on the M3 to Southampton - it's downhill by about 90m so I believe even though there are some significant ups and downs near Southampton and the display showed 69mpg. My calculations show that the reading at that milage is about 7mpg high ie 62mpg true. I drove back (up hill this time) to give 62mpg (or 55mpg true).
Back to the present - I set the tappets and gapped the plugs and did a test drive. I wasn't expecting it but I thought "it's quieter - more like a sewing machine". Within the week I drove from Camberley to Keswick in the Lakes (320miles) and recorded 62mpg (55mpg true) there (up hill again) and a week later 64mpg back (57mpg true).
What also seems to have happened is the mpg local driving rises far more quickly to the mid-50s which is nearer to 50mpg. So its more efficient more quickly but it doesn't get as high with the tappets set correctly.
Thank you for reading and I hope my findings are of interest.
