Honda Jazz flat spot / jerking during acceleration

[guest6479]

Hi Everyone,

I've got a curious problem my Jazz - during acceleration the car jerks or has a flat spot (not sure what to call it exactly). I doesn't happen seem to happen above 60mph at all, when just lightly pressing the accelerator, or if you really put your foot down, just during normal acceleration. It might happen once, or a couple of times getting up to speed.

Does anyone have any ideas of what to try? or experienced the same thing and found a solution? 

Thanks,
Ben

[Jocko]

Have the rear set of spark plugs been changed?

[guest6479]

Thank Jocko - I'll check that out in the morning. It has a service not too long ago so i'm guessing yes, but i'll check with my guy at the garage.

[Jocko]

Lots of garages don't realise that our era Jazz has 8 spark plugs. The second 4 are buried down the back of the engine and are well hidden. Those garages that do know about them often don't change them because of the PITA factor, so a recent service is no guarantee they have been done. Other, well meaning garages, will change the front plugs, see they are not really needing changed, so don't even look at the back ones assuming they will be the same. However it may be several services ago since they were in fact done.

[culzean]

Lots of garages don't realise that our era Jazz has 8 spark plugs. The second 4 are buried down the back of the engine and are well hidden. Those garages that do know about them often don't change them because of the PITA factor, so a recent service is no guarantee they have been done. Other, well meaning garages, will change the front plugs, see they are not really needing changed, so don't even look at the back ones assuming they will be the same. However it may be several services ago since they were in fact done.

+10     

rear plugs are a good place to start,  it is cheap enough to change all 8 so at least you know all plugs are good.

If the rear plugs are neglected for too long it can cause failure of a coil pack,  the coil pack will try to develop enough voltage to jump the ever widening gap as the plugs wear,  if gap has got too wide this can stress coil insulation and cause spark over,  once the insulation has been carbonised it will continue to track over, short circuiting the spark so basically the plug will no longer get a spark,

[guest6479]

Thanks everyone - had a chat with my mechanic and he said he had a look at the rear plugs and thought they looked ok so left them... So I'll get them replaced in the coming days.

culzean - So if the plugs are replaced and we still have the problem, is the coil pack next on the list?

Lots of garages don't realise that our era Jazz has 8 spark plugs. The second 4 are buried down the back of the engine and are well hidden. Those garages that do know about them often don't change them because of the PITA factor, so a recent service is no guarantee they have been done. Other, well meaning garages, will change the front plugs, see they are not really needing changed, so don't even look at the back ones assuming they will be the same. However it may be several services ago since they were in fact done.

+10     

rear plugs are a good place to start,  it is cheap enough to change all 8 so at least you know all plugs are good.

If the rear plugs are neglected for too long it can cause failure of a coil pack,  the coil pack will try to develop enough voltage to jump the ever widening gap as the plugs wear,  if gap has got too wide this can stress coil insulation and cause spark over,  once the insulation has been carbonised it will continue to track over, short circuiting the spark so basically the plug will no longer get a spark,

[Jocko]

had a chat with my mechanic and he said he had a look at the rear plugs and thought they looked ok so left them... 

To me this is a cop-out. No mechanic in the world is going to go to the hassle of checking the rear plugs and not change them. Even if they looked brand new he would still change then rather than have to go through all that again.

[guest3823]

had a chat with my mechanic and he said he had a look at the rear plugs and thought they looked ok so left them... 

To me this is a cop-out. No mechanic in the world is going to go to the hassle of checking the rear plugs and not change them. Even if they looked brand new he would still change then rather than have to go through all that again.

I agree it sounds like he didn't check or change them, maybe didn't know about them, and just said that to cover himself.

I changed all my plugs earlier this year and it was easy. Just got to make sure you take your time and don't cross thread anything. The only thing I found useless was the plug socket from Halfords. It would come off the extension bar in the hole. So I had to use a normal socket to undo the plug then a bit of garden hose to push over the top and pull it out.

[culzean]

Sounds as though mechanic didn't check rear plugs but decided to cover himself just in case you checked them and found that old plugs still fitted.

[degzi]

I recently had a mild flat spot on acceleration, I couldn't pin it down to a certain speed etc.
However I had some redex which I got on the cheap for about £1 seemed to clear it.
The other day I checked my plugs and found that they were quite oily, It looked like someone had put oil or something on the threads and it overheated and gummed the ceramic. I cleaned it off and wire brushed the electrodes while I was at it, its been fine ever since. Checked the gap and it was 1.1mm.

[guest6479]

Hi Chaps,

It took me a while to get it sorted - I ended up changing the spark plugs myself to make sure it was actually done, and done properly.

The sparks looked pretty worn to me (pic attached), and with the new plugs installed it's solved the hesitation/ flat spot problem! (Correct plugs and spacing) Yay! But... the car is still running a little rough with a bit too much exhaust noise - any ideas of what to chase? Faulty coil pack?

 

Thanks for all the help so far

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[Jocko]

With the engine running stick your hand over the exhaust pipe. This will show up any leaks. Check condition of middle box behind offside sill.
Coil pack normally shows up as an OBM code. Do you have access to an OBM reader?

[culzean]

Hi Chaps,

It took me a while to get it sorted - I ended up changing the spark plugs myself to make sure it was actually done, and done properly.

The sparks looked pretty worn to me

Those plugs have been in a long time, gap looks huge ( did you measure it ? )

I know I sound like a worn record with Redex injector cleaner but pop some in,  it is cheap enough and certainly will do no harm.

[guest6479]

The sparks gap was massive probably 2mm! Must have never been changed!

I've made a couple of videos to show what's going on.

1. Intermittent erratic idle -

2. Engine to exhaust noise - not sure if the sound will be good enough to tell what's going on.

Aslo I have one of those wifi ODBII testers, I used it before I changed the spark plugs and there were not errors. Just had a look again now and it's pulling up error "Code P1351 type Powertrain" - I've reset and take her for a spin later and see if it pulls up the same code again...

P.S i'll pick up a bottle of redex asap

[Jocko]

Read this:
http://www.hondafitjazz.com/manual/A00/HTML/98/SAA2E98K72100081155FAAT10.HTML