Worn camshaft?

What varies between load/no load is the hydraulic pressure in the torque converter. When you select drive this pressure acts across the converter nose diameter and pushes your crankshaft forwards. You may have a failed thrust bearing face on the main bearing that deals with end thrust. Possibly the bearing is replaceable without stripping the engine but it may also be the crank shaft thrust face that is badly worn. Lever the crankshaft pulley fore/aft and check for the amount of movement.

There is also the possibility that you hear the flywheel hitting the starter motor. There is very little operating clearance between the starter cog and the flywheel. You may be able to put 1mm of packing under the starter to space it forwards.

Hi Jiri

I'm only commenting on the timing side .... Comments and suggestions via the others are all valid and should not be discounted

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Originally Posted by jiri_j

But my question is, why would this happen ONLY when the engine is under load?

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I had a re-listen of the sound file

Ever owned a manual gearbox car ... and you slowed down to 20kph in top (4th) gear ... then put your foot down to go faster .... and then a rattle noise appears from the motor as a protest from too much load on too low-a revs

Well ... That is what yours sounds like to me ;)



I'll revise my thoughts on timing position and make a suggestion that it is set at TDC or just a bit before TDC

The reason for the motor to rattle, if this was the case, is that with NO LOAD ... There is little resistance, and the motor is able to keep turning in the correct direction ...
BUT ON LOAD ... the motor now has resistance, and then the Piston (Being set at prior to TDC) is in a state of instability and does not know (piston) whether to turn the crank, clockwise or anti clockwise

Hence .... A rattle



So I ask you to check the timing position of the spark and how it progresses on advancing through the revs .... You have the crank angle sensor and it is all advance & controlled via a ECU? .... But try to check it via a timing light if you can

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Originally Posted by jiri_j

Yes please, post here the method. I am happy to check for a loose gudgeon pin!

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I've sent you a PM concerning this ....



Cheers
Mike

Mike I agree with you.

I ment too post a reply a couple of days ago but got side tracked.

Too my ears it sounds like retarded timing under load.

Being a D2 I would start with inspecting the crank angle sensor, and flywheel pickup

Thank you so much guys!!!

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There is also the possibility that you hear the flywheel hitting the starter motor. There is very little operating clearance between the starter cog and the flywheel. You may be able to put 1mm of packing under the starter to space it forwards.

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I would start with checking the clutch - flywheel, drive plate etc then. This could really be the source of the scraping noise on acceleration. This is very difficult to pinpoint, since the engine has to be under load and high rpm to hear it properly. The flywheel could be also the source of timing issues at lower rpm, which I have, since it carries the crankshaft position sensor reluctor ring.

Is there any other way to inspect the clutch assembly without removing the gear box? Probably not :-| Note again that my v8 is manual.

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So I ask you to check the timing position of the spark and how it progresses on advancing through the revs .... You have the crank angle sensor and it is all advance & controlled via a ECU?

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Yes exactly Mike. I can check it real time on my obd2 tool. I will measure advance versus rpm at load/no load conditions. btw I will give you a call if I run out of ideas and will start inspecting the pistons. I appreciate your help!

Cheers Jiri

Hello there, I am back from holidays and ready again for a 'rattle noise' investigation. Just to remind all of you it was a rattle sound at low rpm when the engine is loaded, D2 V8 2001.

I measued the spark advance as a function of rpm. I made three measurements: 1-no load on the engine, 2-going up-hill, 3-when the engine is loaded (going up-hill and braking the same time). There is a pdf attached. The rattling noise came only at the situation #3 at low rpm (600-900rpm). Can I learn anything from this, Mike?

Not sure if it is related, but there was backfiring through an exhaust when reving the engine up to 3500rpm and suddenly releasing throttle. This would confirm a timing issue. When driving the car (no load, high load), there is no backfiring (at least I can't hear any). Backfiring appears only when reving the engine above 3500rpm and suddenly releasing throttle.

What I did so far: I changed spark plugs and wires. The same time I checked for a leaking injector - they work perfectly, no build-up on them. I changed the y-pipe exhaust gaskets. Checked for clogged cats using an inspection camera. Using obd2 I checked these sensors: MAF, intake air temperature, engine coolant temperature, throttle position sensor, 02 sensors. Long term fuel trims -1%. So far found nothing. Tomorrow I want to check the fuel pump for pressure and delivery. Any thoughs?

Attachment 33137

I would get someone to lever the front pulley back and forth and measure the endfloat. Unfortunately if it is excessive, then the bottom end may be irrepairable if the crank thrust bearings are ground away. I have seen one where the crank was actually using the block as a thrust surface eventually:mad:
There was also a very loud knocking as every conrod was being thrust out of alignment by the crank end float.

Being a manual though, I would expect the noise to change as the foot is pressed on the clutch if the crank float is to blame, does this happen?

JC

Hi Justin, I checked the crankshaft and it is solid. Touch wood :) The noise is half the frequency of crankshaft, so I suspect something else - like camshaft or so. The noise appears only when engine is loaded and at very low rpm - this corresponds to low engine oil pressure (around 15 psi). So I was thinking: if there is unsufficient lubrication of lifters (possibly worn), could this produce this kind of noise? As I wrote already I have some backfiring issues as well - reving the engine to 3500rpm and lifting off the throttle suddenly, there is backfiring through exhaust. Could anyone help, please???

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Originally Posted by jiri_j

Hi Justin, I checked the crankshaft and it is solid. Touch wood :) The noise is half the frequency of crankshaft, so I suspect something else - like camshaft or so. The noise appears only when engine is loaded and at very low rpm - this corresponds to low engine oil pressure (around 15 psi). So I was thinking: if there is unsufficient lubrication of lifters (possibly worn), could this produce this kind of noise? As I wrote already I have some backfiring issues as well - reving the engine to 3500rpm and lifting off the throttle suddenly, there is backfiring through exhaust. Could anyone help, please???

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Ah, sorry I couldn't load the sound file, but if it is half the speed of the crank then yes, I would suspect maybe the cam thrust plate, excessive camshaft endfloat? This will cause a scraping noise as the chain is quite close to the case, AND upset engine timing as these engines run a cam position sensor and this can be geting some unpleasant signals by being struck by the cam sprocket.
The oil pump is also driven off the front of the crankshaft.

Removing the timing case is relatively easy, maybe a 'stethoscope' will help isolate the noise?

JC

double post

Your backfiring is probably due to an exhaust leak at or near the head. Nothing to do with timing. It will suck air in on trailing throttle. Probably the engine noise too, as it is consistent with one cylinder firing. Do the garden-hose-stethoscope trick and try to pinpoint the noise. Probably a cracked or damaged exhaust manifold.

A useful tool for finding exhaust leaks is a strip of paper about 1cm wide 5cm long, hold it in long nose pliers or tack it to a dowel, hold it all around the exhaust joints. It will flutter where there is escaping exhaust gas. Saves burning fingers.;)