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Jaf
Joined: 08 Jun 2006
Posts: 194
Location: Oria. Spain
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 Posted: Sat Jul 29, 2006 1:45 am Post subject: Strange clatter |
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Hi,
I'm trying to find a strange clatter on my car. It's quiet upto 2,000 revs. It sounds like big ends except it happens when reving not on the overrun, also the oil pressure is good. It sounds more like in the top of the engine towards the distributor but I've checked the tappets both cold and warm. She has new 95ron unleaded fuel instead of the old 98ron leaded fuel, but altering the timing hasn't helped. Number 1 and 4 plug get a little wet, 4 being worse. When I was trying to get her started a few weeks back the fuel dissy was stuck fully open so there was a lot of fuel in the oil. CO was 8, hydrocarbons 3,000! But have adjusted the mixture now. I have changed the oil 3 times since then. Compression is good at 150psi. I know that the crank is a bit worn but the ends are relatively new (8 years but only a couple of thousand miles). Wondered if it were pre-ignition so checked coil and distributor which are ok. Distributor does have a lot of end play though.
Any ideas what to check?
Thanks,
Jaf
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Chrenan
Joined: 15 Jan 2003
Posts: 3903
Location: Canada
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| Posted: Sat Jul 29, 2006 3:44 am Post subject: Re: Strange clatter |
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| Jaf wrote: | | It sounds more like in the top of the engine towards the distributor... |
There is a small plastic "elbow" that connects to the cam oiler tube at the front of the head. If you take off the cam cover you can see it. It often cracks, the cracks aren't always visible until you take it out. If it is cracked in your car, oil may not be making it to the tappets towards the back of the head (towards the distributor), causing them to sound rough. It is easy to replace and only a few dollars (or pounds in your case).
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1987 951 - M193 Version for Japan |
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Jaf
Joined: 08 Jun 2006
Posts: 194
Location: Oria. Spain
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| Posted: Sat Jul 29, 2006 6:20 am Post subject: Re: Strange clatter |
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| Chrenan wrote: |
There is a small plastic "elbow" that connects to the cam oiler tube at the front of the head. If you take off the cam cover you can see it. It often cracks, the cracks aren't always visible until you take it out. If it is cracked in your car, oil may not be making it to the tappets towards the back of the head (towards the distributor), causing them to sound rough. It is easy to replace and only a few dollars (or pounds in your case). |
Thanks for the idea Chrenan. I had seen a thread on here about the elbow so was fairly sure mine was ok. I've just had another look and turned the engine over by hand to be doubly sure. I'm getting oil fine. I will get another elbow anyway as mine hasn't been replaced since at least 1992.
Any other thoughts?
Thanks,
Jaf
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Jaf
Joined: 08 Jun 2006
Posts: 194
Location: Oria. Spain
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| Posted: Sat Jul 29, 2006 10:59 pm Post subject: Camshaft lobe worn |
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Ok, found wear on one of the camshaft lobes. I'm sure it wasn't there before as I've checked the tappets twice but maybe I just missed it. It's only on one of the lobes so could that be enough to make a racket? It's the inlet lobe.
I'd attach a picture but I can't work out how to do it!
Jaf[/img]
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seanski44
Joined: 13 Mar 2006
Posts: 532
Location: Nottingham UK
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| Posted: Sat Jul 29, 2006 11:07 pm Post subject: Re: Strange clatter |
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| Chrenan wrote: | | Jaf wrote: | | It sounds more like in the top of the engine towards the distributor... |
There is a small plastic "elbow" that connects to the cam oiler tube at the front of the head. If you take off the cam cover you can see it. It often cracks, the cracks aren't always visible until you take it out. If it is cracked in your car, oil may not be making it to the tappets towards the back of the head (towards the distributor), causing them to sound rough. It is easy to replace and only a few dollars (or pounds in your case). |
I know we've had this discussion before, and not wanting to hijack the thread, particularly as the elbow doesn't appear to be the prob, but please remember that this elbow is discontinued at the OPC, so unless we can work out an alternate supplier sourcing one could be worse than 'a few dollars' .
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1998 BMW Z3 2.8 arctic silver & red
1981 168HP 931 S2 blue/tan leather - SOLD 
1985 121HP 924 2.0l na modded - SOLD!
1992 968 lux SOLD
1989 944 2.7 lux SOLD |
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Jaf
Joined: 08 Jun 2006
Posts: 194
Location: Oria. Spain
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| Posted: Mon Jul 31, 2006 6:41 pm Post subject: |
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Have got the car fully road legal so have driven a few very short trips.
On acceleration up to 2,400 revs it's quiet then she starts sounds like a bag on nails when I hit 2,500 revs. If I hold her steady at 2,500 revs she goes quiet again. Then on acceleration to 3,000 revs she clatters again until I hold the revs steady again. The roads are residential (restricted to 30mph) so haven't been able to test much. Don't fancy taking her to the motorway just yet! This is just not a clatter that makes any sense to me. In my experience big ends clatter on the overrun and camshafts clatter all the time.
Any ideas?
Thanks, Jaf
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Jaf
Joined: 08 Jun 2006
Posts: 194
Location: Oria. Spain
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| Posted: Mon Jul 31, 2006 6:51 pm Post subject: |
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Pic of camshaft [img]
[/img]
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Ozzie
Joined: 12 Mar 2005
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Location: Townsville, Qld. Australia
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| Posted: Mon Jul 31, 2006 6:56 pm Post subject: |
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OUch, but not as bad as some I have seen.
Check your ignition timing, sounds like its is too far advanced.
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Jaf
Joined: 08 Jun 2006
Posts: 194
Location: Oria. Spain
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| Posted: Mon Jul 31, 2006 8:13 pm Post subject: |
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| Ozzie wrote: | OUch, but not as bad as some I have seen.
Check your ignition timing, sounds like its is too far advanced. |
Thanks Ozzie.
Timing's dead on 10 degrees. I did wonder if with 95ron fuel instead of 98ron it should be altered? Have tried doing it by ear and couldn't make it any better.
I agree the cam doesn't look too bad compared to other pics on here. Still a worry though. Strangely she doesn't sound like it's a problem. Will keep an eye on it.
Jaf
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Ozzie
Joined: 12 Mar 2005
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| Posted: Mon Jul 31, 2006 8:26 pm Post subject: |
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Been told to drop it back to 8 degrees when on 95.
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Jaf
Joined: 08 Jun 2006
Posts: 194
Location: Oria. Spain
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| Posted: Fri Aug 11, 2006 10:42 pm Post subject: |
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| Ozzie wrote: | | Been told to drop it back to 8 degrees when on 95. |
Thanks again Ozzie. Have started driving her a bit, trying to drive her gently but get a stupid grin on my face and keep going faster, faster, faster. The clatter does seem to be less and only happens between 3,000 and 3,500 revs on acceleration. I'm wondering if all the fuel in the oil stripped some of the oil protection somewhere, except wouldn't that cause a clatter all the time? She's on her 3rd lot of oil so should be well clear of fuel now.
Jaf
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Min
Joined: 04 Nov 2002
Posts: 2368
Location: Vernon, British Columbia, Canada
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| Posted: Sat Aug 12, 2006 6:26 am Post subject: |
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| Jaf wrote: | | Thanks again Ozzie. Have started driving her a bit, trying to drive her gently but get a stupid grin on my face and keep going faster, faster, faster. The clatter does seem to be less and only happens between 3,000 and 3,500 revs on acceleration. I'm wondering if all the fuel in the oil stripped some of the oil protection somewhere, except wouldn't that cause a clatter all the time? She's on her 3rd lot of oil so should be well clear of fuel now. |
you sure your clatter isn't just good old detonation?
Min
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Lizard
Joined: 03 Nov 2002
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Location: Abbotsford BC. Canada
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| Posted: Sat Aug 12, 2006 6:59 am Post subject: |
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see about hooking up an air fuel ratio guage and seeing what your air fuel ratio is doing when this happens,
you have said that the fuel dizzy was stuck open, this to me indicates where to start looking for the issue. and I would say it is fuel delivery, if the arm is not moving properly then that means on accell the arm would stick and slowely catch up meaning that your mix would go really lean and cause the engine grief.
hope that gives you a place to start.
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Jaf
Joined: 08 Jun 2006
Posts: 194
Location: Oria. Spain
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| Posted: Sat Aug 12, 2006 8:15 pm Post subject: |
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| Min wrote: |
you sure your clatter isn't just good old detonation?
Min |
Nah Min, it's a really horrid bag of nails in the engine clatter.
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Jaf
Joined: 08 Jun 2006
Posts: 194
Location: Oria. Spain
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| Posted: Sat Aug 12, 2006 8:21 pm Post subject: |
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| Lizard wrote: | see about hooking up an air fuel ratio guage and seeing what your air fuel ratio is doing when this happens,
you have said that the fuel dizzy was stuck open, this to me indicates where to start looking for the issue. and I would say it is fuel delivery, if the arm is not moving properly then that means on accell the arm would stick and slowely catch up meaning that your mix would go really lean and cause the engine grief.
hope that gives you a place to start. |
Hum, Lizard that's a good next step. Thanks. Will take her to a garage, bung them a few pounds to use their guage. Presume watching the CO and unburnt fuel would be a good enough guage? My only inkling that it's not a fuel problem is the car doesn't miss a beat, doesn't slow or backfire, just accelerates beautifully apart from the clatter. If the fuel dissy was still not right wouldn't the fuel being lean on acceleration cause bad acceleration?
Jaf
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