Rattle and flat spot at around 2000 rpm

[rooser]

Hi,
 I've recently purchased a 2010 Jazz EX that's on about 75K miles. All seems fine other than a strange rattle like a loose heat shield or something when going through 1800 to 2400 rpm in all gears. It seems to coincide however with a bit of a jerking flat spot though, especially in 2nd.

Not sure if they are related, but it's been recently serviced, had new plugs too and I've runa few tanks of Redex through it to try and clean it out.

Has anyone had or come across something similar?

thanks

[coffeecup]

I'd put a new set of ignition coils on, could just be a dodgy one.

Mike

[springswood]

There was a post recently saying it's easy to check ignition coils. Try removing the 12 volt plugs on each in turn with the engine running. If the coil is OK the engine will run rough, if it makes no difference the coil's gone. Of course it could be intermittent, which is always difficult to trace.

[Jocko]

A new set of coils is an expensive way to fault find. It's the sort of thing your Honda dealer would do!

[MartinJG]

I have the same 'rattle' at @ 2000 RPM ish though not aware of any flat spot in power. Only occurs under way. Cannot replicate it stationery so difficult to diagnose. We had a look at the exhaust on the ramp and could not find anything. Came to the conclusion that is some sort of resonance possibly occuring in the exhaust bracket/joint. Irritating

[dave.dakar1]

I have a 2009 and have a similar flat spot issue but without the rattle. I believe my issue is something to do with the Exhaust Gas Recycling valve not working properly or being gummed up with carbon. Your EGR may be knackered?


Sent from my iPhone using Tapatalk

[rooser]

Thanks for all the replies,

I've been looking around and have ERG valves cause the flat spotting before so that could be that, would a dodgy coil show up in the fault codes?

One thing I have been told is that the rattling could well be the input shaft bearing in the gearbox which kind of makes sense as the rattle doesn't happen when revving in neutral. I'm kind of dreading how much that could be!

[Jocko]

Doesn't sound in the least like the gearbox bearing. Mine did it at all revs, the higher the louder. Cost me £324 for a gearbox rebuild including bearings and seals.

[culzean]

Gearbox bearing is a whine that normally first notices in lower gears and than moves up to others if left unfixed, but it is just an annoying noise, will never actually break down and leave the car unusable.... Rattling is more likely fo be broken cat heatshield or heatshield on exhaust further along - rattling can also be knocking or pinking, especially when under load up hill or accelerating.

[sparky Paul]

As others have said, you can rule out the gearbox, that's a whine or grumble, not a rattle.

If it only happens around 2000rpm, have a play with the throttle around 2000rpm and see if you can affect the noise. If the noise comes and goes, it could be engine related, if it's reasonably constant, then it's probably something loose and resonating as culzean suggests.

There are lots of reasons why you could be getting an engine rattle, but best to try to work out where it's coming from first.

[guest334]

First step take it back to the garage, if bought privately then you need a step by step approach as other members have commented.

[Jocko]

Sounds like exhaust heat shield. Could the Atkinson cycle be the "flat spot"?

[culzean]

Sounds like exhaust heat shield. Could the Atkinson cycle be the "flat spot"?

Pretty sure MK2 never got Atkinson cycle,  but VTEC changeover is variable depending on position of loud pedal and revs IIRC

[stesjazz]

run the petrol low until the light comes on, then pour in a bottle of cataclean, and take it for a 20 mile drive using lots of revs, and that should help with any carbon build up in the egr or injectors. i do mine twice a year, as its mainly town driven, and it works wonders for £12!

[madasafish]

You need a systematic approach to find rattles.

As mentioned above, heatshields are a favourite.. Easy to check : try moving them by hand. Ones under the car require car on ramps/pit/lift..

Failed coils should throw up an error code and red light on dash. Failing coils may not.. test as descibed.

Fill car with BP Ultimate petrol and Italian tune up - drive eeverwhere at 5,000 rpm... preferably motorway/dual carriageway for 20 miles without stopping.. Add Cataclean/Forte fuel treatment before.
That will clean valves etc.

If the car has not been serviced regulalry and the plugs changed when due.. all the above is a waste of time.. get it serviced first..