My 1998 1.5LXi Mazda 323 (petrol) is making a diesel rattle occasionally when I'm changing up through the gears. It's the same noise that it makes if I drive in too high a gear, such as going into 2nd before the car is at a sufficient speed.
What is this noise likely to indicate?
Many thanks in advance for your advice....
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Sounds like pinking to me...
This is obviously ignition timing related, and should be checked soon before any heat damage is done to the internals of the engine.
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'Pinking' or 'pinging' is more high pitched,a tinkling sound.This will be a bearing rattle(main and big end),due to overloading the engine by using too high gears.Has it done a high mileage?If so a bit of bearing wear is to be expected .Ther is no facility to alter ign.timing on a modern engine-indeed no way for it to be wrong.
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A friends Xsara was overfuelling like mad which caused pinking on acceleration. Diagnosed by the smell of petrol under the oil filler cap, even though he had been commuting a 40-mile round trip that week. Sniffing the oil might be worth a try if you do a long-ish commute.
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Mike Farrow
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The car has only done 68k miles - mainly from short runs such as my 8 mile each way trip to work.
If it's due to bearing wear is it expensive to fix?
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Short answer is yes. But bearing replacement seems to be very unusual nowadays if car correctly serviced.
A replacement second hand engine might be the cheaper option.However first check the other things that can make a noise- like the alternator , water pump, cam chain (if it has one), drive shafts. All could make a ratle at low revs under large load. Severe pinking can also sound pretty bad and more than a mere tinkle, if provoked.
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I wasna fu but just had plenty.
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Firstly I would suspect a faulty Knock Sensorbut I would expect the Management Light to tell you there is a problem Having said that I have come across fuslty sensors that did not trigger the light as the devise was resonating at the wrong frequency due to ingrese of water. Does the make a noise on the cruise or is it OK then. Has your fuel consumption changed. Regards Peter
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The car did make the noise tonight on the way home, at 60mph in 5th gear accelerating on an incline. Fuel consumption hasn't changed. There's no engine management light as it's a 1998 model.
It has me stumped, but hopefully I can get the excellent local mechanic to listen out for it by taking the car for a spin.
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Thank you. I'll take it to the local mechanic to try to rule out all of the possible sources of the noise that you mentioned.
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Agreed, its more unusual to have pinking (or detonation) these days on a fuel injected car, which uses knock sensors to retard timing if ECU detects a 'pink'
Does the rattle disappear as revs increase and get worse with large throttle openings at low RPM?
Before you spend money on diagnosis, check simple things like the correct plugs are installed with the correct gap.
Good luck.
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Thanks Sprice,
I'll put in a new set of plugs over the weekend as it only costs a fiver for the set. The rattle does disappear as revs increase, and especially in the lower gears. But even when accelerating at 60mph in 5th the noise reappears.
If the new plugs don't fix it I'll visit the mechanic.
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'Pinking' or 'pinging' is more high pitched,a tinkling sound.
I know what you mean, but this can under some circumstances sound like diesel rattle, and I tend to agree with someone later on who said it may be a faulty knock sensor...
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