dci eng. rattle

[onlydiesels]

hi,been reading through a few old posts+found one by sk40 about 1.5 dci eng. rattle (may 2005),and webcode has replied that the noise could be `knock`,and the poss. cause could be a faulty MAF sensor which could be causing overfuelling,has he had this prob on his car and having fitted a new MAF sensor,all is ok again. this seems to be the same fault as i`m experiencing now(1.9dci) and as i`m only getting approx 420 miles to a tankful of fuel which is around 32mpg,it could be that i`m also overfuelling,but theres no excessive black smoke to speak of.
has anyone else had this prob or can anyone give me any values of what i should be looking for when testing the MAF?,but webcode did say in his post that he had to compare his with a known good car to diagnose,so does this mean that the values/testing can`t be trusted anyway??
ps i only drive the car at sensible eng revs (partly due to the noise it`s making)

[onlydiesels]

webcode?? anyone??

[Stranger]

Sorry I can't help but if you post a link to the post that you're talking about it might encourage people to give you an answer, if that makes sense

(to post the link; go into the post, copy the link that shows in your browser window and paste it inbetween url tags in here).

[REDDERS]

O/D, sounds like maff sensor fault.Had mine changed 2 months ago,fuel consumption went from 48mpg on computor/52 mpg actual to 53 on comp./57 actual.I drive around 150 miles a day long journies to 1st customer then stop /start most of the day.

regards martin....

[onlydiesels]

thanks for the replies folks,but i`m having trouble posting the link.
ferkin computers.may be me though!

[AlexB]

As I understand, the MAF sensor in a turbo DCI engine is mostly used in control and adaptive calibration of EGR, VGT turbocharger control and in the patented method of lag reduction. I, probably, missed a few items in this list, such as injection timing and the multiple injection mode... If it is disconnected, you'll get random puffs of smoke in transient modes, abnormal turbo noises (intermittent high-pitch sssss), flat spots, knock and slightly reduced MPG. One may Google around for the relevant articles/patents (this is what I did) or just ask Webcode and LGC...

Rattles may be also caused by a TDC sensor, but it is supposed to throw an error message... The temperature sensors or the thermostat may also cause abnormal noise.

I would imagine that if the offending sensor is just half-dead, then the symptoms may vary.

In any case, start with simple mechanical causes, such as engine mounts, exhaust, air filter box, filter itself, motor oil, EGR valve, etc., and then proceed with reading error codes and more complex diagnostics well documented in Renault papers.

Why don't you record the sound and post it here? It is simple. I did it once when discussing the effect of ester-based oils on cold engine starts in winter.