Hi all is anyone local to me that could give me a second opioion on a problem with a 3.9 rover v8 serp engine. I suspect a worn cam shaft but yet I am not getting any noises like loud tapping or cam chain slap on the timing cover.
Pretty much if I floor it the car will pull all the way upto 95 mph but won't seem to rev or pull past 95 mph which leads me to believe the cam shaft wear or something else is causing the problem but i would like a second opion before I go mad and pull it all apart and replace everything. Thanks Michael I'm near Bradford West Yorkshire.
Can anyone give me a second opinion
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ramon alban
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Hello Woof,
here is a purely diagnostic process to detect a worn cam lobe on a Rover SD1 Efi RV8 Engine, without dismantling any part of the engine.
The Diagnostic Process.
# Warm up the engine and set the idle to a steady and easy to remember speed (say 800 rpm).
# Using suitably insulated grips/pliers, remove one spark plug lead at a time from the distributor (or spark plug) and observe the drop in idle speed for each cylinder.
# Note down the results for each cylinder in turn from No 1 thro 8.
# Removing the plug lead from a normally functioning cylinder will cause a drop in idle speed of approximately 250 rpm (so, from the suggested speed, down to about 550 rpm).
# Removing the plug lead from a cylinder with a badly worn cam will cause a drop in idle speed of approximately 100 rpm (to about 700 rpm).
# Intermediate results between 250 and 100 drop in rpm indicates a degree of partial cam wear.
# It's possible, of course, that a smaller amount of change in idle speed can be caused by a spark plug/lead malfunction which must be eliminated by substitution before blaming the cam.
# Detection of a small (say 100 rpm) drop in idle speed (not due to spark plug/ lead issues ) now really warrants a visual inspection of the cam function. See rationale, below.
# So only if found to be necessary, removal of a rocker cover will confirm any faulty valve lifting issues (on Efi models this is only possible on the L/H bank after removing the plenum chamber).
# Dealing with any intermediate results may warrant dismantling further as explained, but might also be taken together with assessing further symptoms of probable cam wear as follows:
o Idling seems to be OK but raising the engine speed to (say) 2000 rpm induces significant jerking/vibration (as if a plug lead is removed) which then partly diminishes at higher rpm.
o Not easy to detect, but a general loss of all round performance over long periods of time.
o the spark plug on a cam-affected cylinder may be partially fouled with oil/carbon deposits.
# Obviously, not all engines are the same and a degree of judgement is going be called for but if the specified dynamic test process causes the idle speed to fall by the approximate maximum 250 rpm on all eight cylinders, then its very unlikely that the camshaft is worn.
The Rationale.
On a normally functioning engine, each cylinder contributes an equal amount of energy or torque to the overall output of the engine enabling it to idle smoothly at the chosen test rpm. Removing a spark plug lead has a significant effect on the output rpm fo two reasons.
1) One eighth of the total amount of energy has been lost and 2) The other seven functioning cylinders now have to work harder to compress the fuel/air mixture in the non working cylinder as well as keep the engine ticking over at the best speed it can achieve. Usually, a drop of 250 rpm.
When an engine has a badly worn cam, whilst it's still possible to adjust the idle speed to the chosen test rpm, the idle may not be perfectly smooth because the cylinder with the worn cam is making little or no contribution of energy/torque to the overall engine output. Disabling a good cylinder still has an effect similar to that described above, but removing the spark plug lead from a cam affected cylinder detracts very little from the test rpm.
At the same time, the energy required to compress the fuel/air mixture in a non functioning cylinder is less because either the induction and/or the exhaust valves are only opening a small amount. With this double jeopardy, the drop in idle speed is much less than that caused by disabling a good cylinder. Usually falling by typically 100 rpm.
The partial fouling of the spark plug on a cam affected cylinder is expected, especially on an Efi engine, because of a potentially rich mixture due to the inadequate induction of a full volume of air whilst at the same time the normal amount of fuel has been injected into the inlet tract by the ECU.
By performing the dynamic test process it's possible to pre-assess the condition of the camshaft without recourse to removing the plenum chamber or ant other parts of a Rover SD1 Efi V8 engine.
Please feel free to critique, comment and/or improve upon this process and let me have any considered corrections as you deem appropriate. Otherwise also feel free to contact me regarding Errors and Omissions.
Not sure if it would work on an engine where the problem only appears at 95 mph though?
here is a purely diagnostic process to detect a worn cam lobe on a Rover SD1 Efi RV8 Engine, without dismantling any part of the engine.
The Diagnostic Process.
# Warm up the engine and set the idle to a steady and easy to remember speed (say 800 rpm).
# Using suitably insulated grips/pliers, remove one spark plug lead at a time from the distributor (or spark plug) and observe the drop in idle speed for each cylinder.
# Note down the results for each cylinder in turn from No 1 thro 8.
# Removing the plug lead from a normally functioning cylinder will cause a drop in idle speed of approximately 250 rpm (so, from the suggested speed, down to about 550 rpm).
# Removing the plug lead from a cylinder with a badly worn cam will cause a drop in idle speed of approximately 100 rpm (to about 700 rpm).
# Intermediate results between 250 and 100 drop in rpm indicates a degree of partial cam wear.
# It's possible, of course, that a smaller amount of change in idle speed can be caused by a spark plug/lead malfunction which must be eliminated by substitution before blaming the cam.
# Detection of a small (say 100 rpm) drop in idle speed (not due to spark plug/ lead issues ) now really warrants a visual inspection of the cam function. See rationale, below.
# So only if found to be necessary, removal of a rocker cover will confirm any faulty valve lifting issues (on Efi models this is only possible on the L/H bank after removing the plenum chamber).
# Dealing with any intermediate results may warrant dismantling further as explained, but might also be taken together with assessing further symptoms of probable cam wear as follows:
o Idling seems to be OK but raising the engine speed to (say) 2000 rpm induces significant jerking/vibration (as if a plug lead is removed) which then partly diminishes at higher rpm.
o Not easy to detect, but a general loss of all round performance over long periods of time.
o the spark plug on a cam-affected cylinder may be partially fouled with oil/carbon deposits.
# Obviously, not all engines are the same and a degree of judgement is going be called for but if the specified dynamic test process causes the idle speed to fall by the approximate maximum 250 rpm on all eight cylinders, then its very unlikely that the camshaft is worn.
The Rationale.
On a normally functioning engine, each cylinder contributes an equal amount of energy or torque to the overall output of the engine enabling it to idle smoothly at the chosen test rpm. Removing a spark plug lead has a significant effect on the output rpm fo two reasons.
1) One eighth of the total amount of energy has been lost and 2) The other seven functioning cylinders now have to work harder to compress the fuel/air mixture in the non working cylinder as well as keep the engine ticking over at the best speed it can achieve. Usually, a drop of 250 rpm.
When an engine has a badly worn cam, whilst it's still possible to adjust the idle speed to the chosen test rpm, the idle may not be perfectly smooth because the cylinder with the worn cam is making little or no contribution of energy/torque to the overall engine output. Disabling a good cylinder still has an effect similar to that described above, but removing the spark plug lead from a cam affected cylinder detracts very little from the test rpm.
At the same time, the energy required to compress the fuel/air mixture in a non functioning cylinder is less because either the induction and/or the exhaust valves are only opening a small amount. With this double jeopardy, the drop in idle speed is much less than that caused by disabling a good cylinder. Usually falling by typically 100 rpm.
The partial fouling of the spark plug on a cam affected cylinder is expected, especially on an Efi engine, because of a potentially rich mixture due to the inadequate induction of a full volume of air whilst at the same time the normal amount of fuel has been injected into the inlet tract by the ECU.
By performing the dynamic test process it's possible to pre-assess the condition of the camshaft without recourse to removing the plenum chamber or ant other parts of a Rover SD1 Efi V8 engine.
Please feel free to critique, comment and/or improve upon this process and let me have any considered corrections as you deem appropriate. Otherwise also feel free to contact me regarding Errors and Omissions.
Not sure if it would work on an engine where the problem only appears at 95 mph though?
I don't think it will do would be fun trying it at that speed though lol. I can run it on tick over with no Change in rpm that's the strange thing. Haven't tried all off them yet. I'm going to do a compression test at some point in the week see if any cylinders are down in compression. I would love a extra view on it before I go mad and pull the engine in bits and just do it.
Land rover discovery 3.9 Hotwire v8 nick named Christine.
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ramon alban
- Knows His Stuff
- Posts: 667
- Joined: Fri Nov 17, 2006 11:22 pm
- Location: Bedford UK
- Contact:
How can that be, when:I can run it on tick over with no Change in rpm that's the strange thing.
Unless the cam on the cylinder you tried is bad or the procedure is flawed?# Removing the plug lead from a normally functioning cylinder will cause a drop in idle speed of approximately 250 rpm (so, from the suggested speed, down to about 550 rpm)
Thought I'd posted this yesterday, but it's not appeared...Big woof wrote:I don't think it will do would be fun trying it at that speed though lol. I can run it on tick over with no Change in rpm that's the strange thing. Haven't tried all off them yet. I'm going to do a compression test at some point in the week see if any cylinders are down in compression. I would love a extra view on it before I go mad and pull the engine in bits and just do it.
A cranking compression check won't show up a worn cam - until it is so worn the valves no longer open.
Since it's the top of the lobe which wears most, a dial gauge on each tappet might show a difference?
If it's done high miles - say over 100,000 and or had oil changes neglected there's a good chance an original needs changing. After market ones might have an even shorter life.
However, it's pretty obvious when you get to see it, and taking off the inlet manifold doesn't take long.
Dave
London SW
Rover SD1 VDP EFI
MegaSquirt2 V3
EDIS8
Tech Edge 2Y
London SW
Rover SD1 VDP EFI
MegaSquirt2 V3
EDIS8
Tech Edge 2Y
Hello Dave I think you might be right I haven't got Amy service history with the car when I bought it. I did a oil change and a small service over time on it. Cured quite a lot off problems with the engine electrics and the air leaks that the engine has had. A compression test is to double check that they has been no damage to the valves or pistons. The only thing that I can't understand is why I ain't getting any noises from the engine like tapping or clattering from the timing chain
I think that the safest bet is just to buy a cam and all the bits that are needed to do the job and just replace the cam shaft. Was thinking off the real Steel cyclone cam shaft. Or can anyone recommend a decent cam shaft kit to look at buying or is it just lay my hands on a std cam shaft for the engine from the dealers
I think that the safest bet is just to buy a cam and all the bits that are needed to do the job and just replace the cam shaft. Was thinking off the real Steel cyclone cam shaft. Or can anyone recommend a decent cam shaft kit to look at buying or is it just lay my hands on a std cam shaft for the engine from the dealers
Land rover discovery 3.9 Hotwire v8 nick named Christine.
Could be I think that the replacement Ecu came out off a 1997 automatic v8 3.9 14 cux I was thinking that myself. I have replaced quite a few failed components on just about every part off the car.
Here's the list.
Leads cap rotor arm plugs fuel pressure regulator fuel pump ignition module and coil Ecu temp sensor stepper motor Ecu alarm box a host off relays that was faulty and corroded sealed the steppe motor housing to the plenum. Plenum to the inlet manifold. One lamba sensor throttle position sensor and gasket set the advancement off the engine and the base idle once the plenum was sealed up.
Here's the list.
Leads cap rotor arm plugs fuel pressure regulator fuel pump ignition module and coil Ecu temp sensor stepper motor Ecu alarm box a host off relays that was faulty and corroded sealed the steppe motor housing to the plenum. Plenum to the inlet manifold. One lamba sensor throttle position sensor and gasket set the advancement off the engine and the base idle once the plenum was sealed up.
Land rover discovery 3.9 Hotwire v8 nick named Christine.
-
ramon alban
- Knows His Stuff
- Posts: 667
- Joined: Fri Nov 17, 2006 11:22 pm
- Location: Bedford UK
- Contact:
Many many thousands of these (standard) engines have run for even more thousands of miles with absolutely no problems.Big woof wrote:Hi Dave it's just that I don't like the ideas off plastic timing gears that's all had some bad experiences with timing components made from plastic
Other thing is much aftermarket stuff is of poor quality. And knowing where you can get steel cogs which are well made isn't necessarily easy. Same with chains.
Dave
London SW
Rover SD1 VDP EFI
MegaSquirt2 V3
EDIS8
Tech Edge 2Y
London SW
Rover SD1 VDP EFI
MegaSquirt2 V3
EDIS8
Tech Edge 2Y
