Fixing the niggles on a 14 Year Old SE Manual

[guest5589]

So I know that this has been discussed to death in these forums but I have read most of the threads and my situation sort of sounds similar but isn't.

a. Flat Spot:
I have noticed that in 1st gear half throttle acceleration, just as I reach around 2500 there is a very noticeable gap in acceleration for a second and then it resumes with a lesser rate.

b. Bucking at Low speeds:
 Also since last week the car seems to have started 'bucking' as many threads put it and finally I know what they meant. Happens mostly on part throttle, half clutch situations when crawling in London traffic. EGR I have cleaned a few times, checked front and back plugs (2 of them at random) and they look fine so just wondering what could it be.

The air filter is about 5000 miles old so don't suspect thats the cause.

c. Noise Vibration Harshness
Although there are no knocks or bangs in the suspension, on bad surfaces the car seems to let a lot of vibration in. I have driven a lower mileage Jazz of same age and it felt much more compliant and softer than my one on same 15" alloys so I was wondering if I can do anything to improve the NVH?

[culzean]

First and cheapest thing to try for most engine woes is a good dose of redex - in an older car put a whole bottle in - it won't do any harm and better to have more for first treatment.

[gtd2000]

So I know that this has been discussed to death in these forums but I have read most of the threads and my situation sort of sounds similar but isn't.

a. Flat Spot:
I have noticed that in 1st gear half throttle acceleration, just as I reach around 2500 there is a very noticeable gap in acceleration for a second and then it resumes with a lesser rate.

b. Bucking at Low speeds:
 Also since last week the car seems to have started 'bucking' as many threads put it and finally I know what they meant. Happens mostly on part throttle, half clutch situations when crawling in London traffic. EGR I have cleaned a few times, checked front and back plugs (2 of them at random) and they look fine so just wondering what could it be.

The air filter is about 5000 miles old so don't suspect thats the cause.

Have you ever changed the rear set of plugs?

Check the electrode gaps - that may well cure both of the above.

[guest5589]

I haven't changed either set as I have done about 9000 miles since acquiring the car but checked them recently and they looked same as front but I think they are cheap to replace so will order some along with some Redex. I'm thinking of running some BP 99 just for a tank full as I have been running on Asda for a while and although my Yaris would know the difference between the two, Jazz has never complained in terms of mpg or power.

[culzean]

I would try redex first as it is cheapest option, and my old engineers brain tells me that you should never change or try more than one thing at a time as you never know which change cured the problem.

[gtd2000]

I haven't changed either set as I have done about 9000 miles since acquiring the car but checked them recently and they looked same as front but I think they are cheap to replace so will order some along with some Redex. I'm thinking of running some BP 99 just for a tank full as I have been running on Asda for a while and although my Yaris would know the difference between the two, Jazz has never complained in terms of mpg or power.

A set of plugs ( 8 ) is around £13 delivered from EuroCarParts.

Our Jazz ran perfectly and returned great MPG but then started kangarooing...went down the route of the EGR etc that everybody else says to check and it was as clean as a whistle...

I'm fairly sure many people get their Honda Jazz serviced by mechanics that have no clue about the rear set of plugs...I never knew about them either, until one lone wolf (who was ignored mainly by other posters) suggested that it could be the rear set of plugs...folks still kept going on about the problems though...and the EGR.

As soon as I pulled the plugs I could see they were worn and the gaps were totally out of spec. I re-gapped them until the replacements arrived and the car ran just fine after that - that was over a year ago now and no kangarooing has ever been experienced since.

[guest5970]

Have recently been through this exact same process - as far as the flat spot goes; agree with gdt2000 - issue was sorted the moment new rear plugs went in. I bought a new EGR because of all the chatter on this forum; but haven't needed to fit it.

NVH - 2-stage cure (NB - am on 14" wheels - makes things easier):

First stage is to fit good quality Euro tyres, of a model that explicitly prioritises quietness. I chose Pirelli Cinturato 1 Eco Verde - absolutely transformed the noise/harshness issue in a 2002 1.4 SE. Obviously wet grip is first rate as well. Most of the noise seems to come through the front struts.

Second stage for me was to replace rear shockers with KYB Excel-G, & the springs with KYB - these combined transformed the choppy ride of my 85K miler to a nicely damped ride as good as or rather better than a chum's low-mileage 2007 model. KYB are a huge Japanese manufacturer of OEM suspension parts and specifically tune these replacements to the dynamics of an old vehicle.

So I know that this has been discussed to death in these forums but I have read most of the threads and my situation sort of sounds similar but isn't.

a. Flat Spot:
I have noticed that in 1st gear half throttle acceleration, just as I reach around 2500 there is a very noticeable gap in acceleration for a second and then it resumes with a lesser rate.

b. Bucking at Low speeds:
 Also since last week the car seems to have started 'bucking' as many threads put it and finally I know what they meant. Happens mostly on part throttle, half clutch situations when crawling in London traffic. EGR I have cleaned a few times, checked front and back plugs (2 of them at random) and they look fine so just wondering what could it be.

The air filter is about 5000 miles old so don't suspect thats the cause.

c. Noise Vibration Harshness
Although there are no knocks or bangs in the suspension, on bad surfaces the car seems to let a lot of vibration in. I have driven a lower mileage Jazz of same age and it felt much more compliant and softer than my one on same 15" alloys so I was wondering if I can do anything to improve the NVH?

[guest6326]

I have issue with bucking when crawling.....

No idea of previous owners ever use redex or not.

I've put about half bottle in a full tank, and left it out on the second full fill. 
I'll be putting the last half in next time I fill of at least half a tank...

I had a service done when I got it, along with the MOT...

But still see to be jumping.

Any other suggestions on what to try?

[guest5970]

I'd go up the ignition tree: plugs, then coils, then leads . . .  if all OK, then switch focus to the EGR valve - there's enough anecdotal evidence here that replacement/cleaning can be a cure.

[guest5589]

I had a deep look at the engine bay and observed whats happening. took the intake off to see the condition of the TB and it wasn't too bad but cleaned it a bit with electronic contact cleaner but finally swapped out my old and throuhgly worn earth strap with one supplied by TG and I don't know if it was due to battery off that the idle got reset or because the earth strap was held together by just a couple of strands of wire but now the car runs beautifully.. no bucking whatsoever..

haven't done enough mileage to confirm but things can only get better from here..

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[guest5970]

  . . . well, 14 years is long enough for *anything* to go. Yet another thing to check/replace . . . .

[guest5589]

Just came back from a 50miles round trip @58.7mpg.
Absolutely no bucking or similar symptoms... crawling in traffic the car behaved very well and the throttle response was wonderfully linear :O

This might have done the trick tbh..

[guest1372]

I think a reset and throttle body inspection/clean are probably the cure rather than that earth strap.  I have no idea without going out to look but don't think it's the sole earth connection between engine/gearbox and body.  Every earth on the block would be well interconnected, if not all sort of ECU issues could probably arise.

Looking at the earth strap I wonder why they didn't cover the whole thing in conduit.

I notice that after a battery disconnection the area near the throttle body is very clicky or ticky until the car has had a decent run.
--
TG

[guest5589]

I agree that a simple strap can't be the only thing responsible for this. I do know  that after disconnecting battery the car needs to re-learn idle and one needs to let it figure that out by leaving it alone. First start after re-assembly the car sounded very weird and had a bit of hunting idle but now it has settled between 1K & 5k mark.

Previously on aggressive throttle in 3rd gear the car would be slow to respond but now it just pulls.

[culzean]

You have to give redex time to dissolve off accumulated crud on injector nozzles etc. Especially if car has gone a long time without such treatment, I have found found over the year's that good oil and redex are an engines best friends - and are money well spent.  There are several earth straps running from bodywork to engine but first thing I do when I get a car is to run a braided strap direct from battery negative to the engine block and this bypasses all the dodgy rusty connections between straps and steel body work,  Halfords  do a plated copper braid  one 24" ( 600 mm long) for about £7 - it does not need to be insulated.