Technical Bravo stutter/slipping sound. What?

[thesmallprint]

Hello. '08 Bravo 1.9 150 Sport here, and under medium acceleration from slow-med speeds (across gears 2-3 at least) it makes a really odd sound, like something slipping. Doesn't sound like crunching metal, and there are no rev fluctuations so I doubt it's clutch, but you can feel it as a slight loss of power on each sound. It doesn't happen all the time. Hard acceleration seems fine, as does very gentle acceleration. I don't think I've ever heard it in gear 4+ or in 1. Does anyone have any ideas?

Video attached.

[ame="https://youtu.be/y_wN_RaAh4w"]https://youtu.be/y_wN_RaAh4w[/ame]

 

[thesmallprint]

This post seems to have got lost in the flood of clutch clip resurrections, but I'd be really interested to have some opinions. Anyone heard anything like that before? Sounds like something slipping or rubbing, but not at the same rate the wheels are going around, and you CAN feel it through little losses of power so it's not just the V-belt or something. No rev fluctuations either. It's a puzzle.

 

[thesmallprint]

An update. It turns out the sound was: impending doom. Ended in a rattle and complete loss of power. Now in garage to see if it's gearbox or clutch, and whether it can be rebuilt or if it's time for a bucket of oats and a shotgun.

Will update more once he's had a look in its guts.

 

[thesmallprint]

So, DMF had gone, damaged the clutch too. With that, and replacing both rear coil springs (one had cracked), I'm down just under £1000. Not my best birthday ever...

Will update when I've driven it to check if the hushing sound was related to the clutch failing or if it's a separate issue. I really hope not.

 

[Matthen]

Thanks for updating, I've been watching with interest. I feel your pain! Its been an expensive motoring month for me as well.


Hopefully that'll be everything for the next year or so at least!

 

[thesmallprint]

Update: so that wasn't the sound of impending doom. The flywheel was a separate issue, which has been repaired and the clutch feels light and responsive now, but the car is still making that hushing sound. Usually just under 2800rpm, accelerating and turning. It's quite hard to make it do it, but sometimes it still does. The mechanic hadn't noticed it but he only gave it a quick run to see if it went and if it was leaking from the transmission since it'd had a damaged seal down there. I'm hesitant to take it back to get an opinion just yet as what with car repairs and tuition fees I've already spent more than £2k today, and none of it was on anything fun.

 

[bgpro]

Hello thesmallprint. Did you get the car back for another opinion in the end? My Bravo does the exact same noise (and power loss) under medium acceleration, but no mechanic so far over here seems to know where this problem comes from. It's been like this for years, some days it happens more often than others, but it's really annoying because some day it will probably fail completely.

 

[thesmallprint]

No, I've got an odd situation with my car in that I can't keep it at my house, so I don't actually get to drive it that much. I can tell you a lot of things it isn't: not the clutch (which is new), not the wheels nor tyres, not the performance chip. I've had MES hooked up to it as it goes along and watched every sensor I thought might be related and nothing. It sounds like pressure venting but boost pressure's fine, actuators for all the pressure systems don't seem to trigger in bursts like that.

I think the only way to be sure would be to get it on a dyno while it's hooked up to MES, and pin down *exactly* the conditions, and maybe have the bonnet open to see exactly where the sound's coming from, but that's expensive.

Far as I can tell it's worst in 2nd-3rd at 2800-3000rpm, in gradual acceleration. If you hoof it, it goes away. Same if you back off, but I've felt it as low as 2100 rpm, and can make it do it in 1st as well, though that's much rarer. Honestly it puzzles the hell out of me, and it's the only thing stopping me from fully enjoying the car, because I really do love driving the Bravo. Much nicer than prev Polo or Corsa, especially when it had the chip on and some nice new Conti PC6s on the front.

 

[bgpro]

Thank you for the update! Mine does it sometimes, especially in 2nd under medium acceleration, as you said. Now that it got colder, this doesn't happen as often as before, but it could be unrelated to the temperature. Also, it often does what it sounds like the same noise to my untrained ears when I release the throttle pedal, but in this case there is no sudden power loss (obviously ). To be honest, my only concern is that it makes me think I can't rely on the car for longer trips, although this behaviour has been there since I got the car 3 years ago.

Please keep me posted if you ever find out what it is and I will do the same.

 

[thesmallprint]

I did think of something after writing that last night: check your air box. When I changed my air filter, I found one clip gone, the box open and the other clip rusted badly. That had been letting debris get into the MAF sensor, which is why I checked it. I now wonder if that's come loose again and is affecting the air flow into the engine? Worth checking, anyway.

 

[bgpro]

Thanks thesmallprint, that's quite an easy one, I will check! On the other hand, the car was regularly serviced, but who knows?

 

[bgpro]

I'm wondering if this could be related to the boost solenoid. Possibly a very stupid idea, but I've seen videos on youtube of various cars with somewhat similar symptoms that took me to this idea.

 

[thesmallprint]

I'm wondering if this could be related to the boost solenoid. Possibly a very stupid idea, but I've seen videos on youtube of various cars with somewhat similar symptoms that took me to this idea.

Not a stupid idea at all. Car has finally got an engine light on and limp mode, with code P2009 - Flow shutter valve and P0237 - Turbo pressure. I had a look to see if there was any melted wiring, but on a cold winter day I didn't really want to feel my way not knowing what I was doing. Taking it into the garage tomorrow, will update as and when.

 

[bgpro]

Sorry to hear that. Mine still does the same occasionally after replacing the boost solenoid last week, must be something else. I hope your issue has an easy fix.

 

[thesmallprint]

Yeah, no luck. He took off the boost valve and cleaned it out, but his theory was that it had previously been mapped badly and so was reaching peak boost too soon and backing up. He didn’t have the equipment to check the ECU map so he suggested I go to a tuner to get that sorted. I don’t know if he was right or if he just didn’t want to work on it, but his basis was that it seemed to have more power than any of the other bravos he had worked on. Wasn’t me asking the questions so that may have been because he’d only had some 120HP models in before... no idea. Still not really convinced

Unfortunately my insurance company just said ‘f*** off mate’ when I suggested putting the chip back on, so if it’s been mapped I don’t want to know. Would be expensive to check, and disappointing to have to get them to restore factory settings if that was the case. Honestly I’ve learned to just drive around the fault.

 

[bgpro]

Thanks for the update. Now I'm wondering if mine has ever been remapped, but I doubt that (it was a company fleet car before I bought it). Mine is an 120HP model, but can't easily check it against another one in terms of power as this model isn't very popular around where I live. I'll just have to live with it, I guess, until it eventually breaks

 

[davidthelodge]

I had a Croma 1.9 M/jet 16v 150hp and I had this noise. There is a thread on the Croma section. My best description was that it sounded like 2 rubber mats being rubbed together. I changed many parts (MAF sensor, MAP sensor, boost control value, EGR twice, I tried a bullit plate in EGR value, this made it slightly better.

I have a suggestion for you, block off the EGR value with a blanking plate available off ebay, the EML will come on however if its the same fault as I had the noise will go away, dont ask me why !

In the end the garage and I concluded it was caused by a faulty or partially blocked DPF or faulty turbo.

 

[thesmallprint]

@dvid: interesting. In my case it's not a DPF, because it hasn't got one. Lucky for me as I don't do a lot of motorway driving. About your EGR blank: in one line you said it got slightly better and in another it went away. Which is it? If that actually fixed the problem, I might try it, though I suspect the mod is illegal, so I'd test it as a diagnostic rather than a permanent mod. Also in your case if it was a blocked DPF then blanking the EGR probably would help, but not sure it would when there's no DPF.

You've given me some things to think about! Cheers.

 

[davidthelodge]

Mine was much better with a bullit plate fitted in the EGR (i.e. a plate with holes in to restrict the air flow). EML did not come on.

The noise disappeared totally when the EGR was blanked off totally with a blanking plate, (with no holes in it). Of course the EML then came on.

I replaced the original EGR valve twice, (I wondered if the 1st replacement was also faulty, but the noise was just the same with the 2nd replacement. So just to be clear all 3 EGR's gave same result.

I was also told it could be sticking veins as these turbo's fitted have variable veins that should move.

Sold my 1.9 150bhp and now have a 2.4 200bhp Croma

 

[thesmallprint]

So to anyone reading this thread for their own similar problem, it does seem to be the EGR in my case also. Blanking it off removed the problem as far as I can tell, though for legal and insurance reasons I removed the blank before taking it back on public roads, and ordered a new EGR. Not entirely hopeful, but it was £26 off ebay so if it works it works, if it doesn't I haven't lost much. Will update.