Mystery problem Speed 6
Discussion
Hello,
Car : 2005 MK2 4.0L Tuscan, 44.000 Km
Problem: persistently running irregular, slightly improving when properly(>1h running) warm, when cold running on five cylinders and always slow throttle response
So the dealer did a compression test of the six cylinders ......... ALL compression figures where above 11,5 ore around that but cylinder ONE (Not SIX) showed a figures of more then 16 !!!!!
Cylinder SIX exhaust is around 220 degrees whereas the others are around 330 degrees which is normal.
Is there somebody who has an explanation and can it be cured. Can this cause the symptoms?
We found also oil around the spark plugs!!!
PS. Endoscopic inspection of the engine "interior" is healthy.
Koen
Car : 2005 MK2 4.0L Tuscan, 44.000 Km
Problem: persistently running irregular, slightly improving when properly(>1h running) warm, when cold running on five cylinders and always slow throttle response
So the dealer did a compression test of the six cylinders ......... ALL compression figures where above 11,5 ore around that but cylinder ONE (Not SIX) showed a figures of more then 16 !!!!!
Cylinder SIX exhaust is around 220 degrees whereas the others are around 330 degrees which is normal.
Is there somebody who has an explanation and can it be cured. Can this cause the symptoms?
We found also oil around the spark plugs!!!
PS. Endoscopic inspection of the engine "interior" is healthy.
Koen
Koen,
That does seem rather a high figure for cylinder one. To put it into imperial terms a difference of 65 psi. A difference of 15-20 psi or more between cylinders over all is generally considered to be an indication of the onset of wear and tear.
You mention that you found oil around the spark plug on 1, but you do not say if it was burnt oil (brown/black crusty deposits on the plug electrodes if you are burning enough oil the plug will smell acrid) or if it was liquid (unburnt) oil. If it was unburnt oil then this could be a reason for the higher compression. If there is enough oil and it is sitting on the piston rings it will improve the seal and the compression reading will be higher. You do not mention if you have to top up your oil tank very often. If you do then this would suggest that you have either worn rings or valve guides and from your brief I would suspect on cylinder one. The fact that the compression is so high on cylinder one I believe would suggest the rings are fine. My thoughts lead me to suspect the valve guides. I am not sure what tests can be done to disprove the guides are worn without removing the head. However having said all that, I would have expected that for such a volume of oil to be leaking into cylinder 1 to increase the compression...... I would have though the car would be blowing blue smoke out of the drivers side (yours is a left hooker?) rear tail pipe, or at least it will be very sooty black. Perhaps somebody else can add to this? Or correct the analysis? Does anyone know if an exhaust gas analyser reading can indicate burning oil? I am sorry but this is all I can offer with my limited knowledge.
Good luck
That does seem rather a high figure for cylinder one. To put it into imperial terms a difference of 65 psi. A difference of 15-20 psi or more between cylinders over all is generally considered to be an indication of the onset of wear and tear.
You mention that you found oil around the spark plug on 1, but you do not say if it was burnt oil (brown/black crusty deposits on the plug electrodes if you are burning enough oil the plug will smell acrid) or if it was liquid (unburnt) oil. If it was unburnt oil then this could be a reason for the higher compression. If there is enough oil and it is sitting on the piston rings it will improve the seal and the compression reading will be higher. You do not mention if you have to top up your oil tank very often. If you do then this would suggest that you have either worn rings or valve guides and from your brief I would suspect on cylinder one. The fact that the compression is so high on cylinder one I believe would suggest the rings are fine. My thoughts lead me to suspect the valve guides. I am not sure what tests can be done to disprove the guides are worn without removing the head. However having said all that, I would have expected that for such a volume of oil to be leaking into cylinder 1 to increase the compression...... I would have though the car would be blowing blue smoke out of the drivers side (yours is a left hooker?) rear tail pipe, or at least it will be very sooty black. Perhaps somebody else can add to this? Or correct the analysis? Does anyone know if an exhaust gas analyser reading can indicate burning oil? I am sorry but this is all I can offer with my limited knowledge.
Good luck
yzf1070 said:
Koen,
That does seem rather a high figure for cylinder one. To put it into imperial terms a difference of 65 psi. A difference of 15-20 psi or more between cylinders over all is generally considered to be an indication of the onset of wear and tear.
You mention that you found oil around the spark plug on 1, but you do not say if it was burnt oil (brown/black crusty deposits on the plug electrodes if you are burning enough oil the plug will smell acrid) or if it was liquid (unburnt) oil. If it was unburnt oil then this could be a reason for the higher compression. If there is enough oil and it is sitting on the piston rings it will improve the seal and the compression reading will be higher. You do not mention if you have to top up your oil tank very often. If you do then this would suggest that you have either worn rings or valve guides and from your brief I would suspect on cylinder one. The fact that the compression is so high on cylinder one I believe would suggest the rings are fine. My thoughts lead me to suspect the valve guides. I am not sure what tests can be done to disprove the guides are worn without removing the head. However having said all that, I would have expected that for such a volume of oil to be leaking into cylinder 1 to increase the compression...... I would have though the car would be blowing blue smoke out of the drivers side (yours is a left hooker?) rear tail pipe, or at least it will be very sooty black. Perhaps somebody else can add to this? Or correct the analysis? Does anyone know if an exhaust gas analyser reading can indicate burning oil? I am sorry but this is all I can offer with my limited knowledge.
Good luck
Grahm,That does seem rather a high figure for cylinder one. To put it into imperial terms a difference of 65 psi. A difference of 15-20 psi or more between cylinders over all is generally considered to be an indication of the onset of wear and tear.
You mention that you found oil around the spark plug on 1, but you do not say if it was burnt oil (brown/black crusty deposits on the plug electrodes if you are burning enough oil the plug will smell acrid) or if it was liquid (unburnt) oil. If it was unburnt oil then this could be a reason for the higher compression. If there is enough oil and it is sitting on the piston rings it will improve the seal and the compression reading will be higher. You do not mention if you have to top up your oil tank very often. If you do then this would suggest that you have either worn rings or valve guides and from your brief I would suspect on cylinder one. The fact that the compression is so high on cylinder one I believe would suggest the rings are fine. My thoughts lead me to suspect the valve guides. I am not sure what tests can be done to disprove the guides are worn without removing the head. However having said all that, I would have expected that for such a volume of oil to be leaking into cylinder 1 to increase the compression...... I would have though the car would be blowing blue smoke out of the drivers side (yours is a left hooker?) rear tail pipe, or at least it will be very sooty black. Perhaps somebody else can add to this? Or correct the analysis? Does anyone know if an exhaust gas analyser reading can indicate burning oil? I am sorry but this is all I can offer with my limited knowledge.
Good luck
I'm not sure I quite agree with the 15-20 psi being an indication of wear (I was always lead to belive that 10% variance bewteen highest and lowest was acceptable on anything but a newish engine).
The rest of your diagnosis I think is absolutely spot on.
1. check if fuel injector leaking
2. disconnect oil vapour pipe from air filter body
and keep engine running 3 min without pipe connected
before retesting!
Cylinder 1 is too high, i would recheck again
(with pressure loss test)
Cylinder 6 i would check throttle adjustment, if flow is low temp is also low.
(But it is better to keeep cyl 6 a bit down because of
danger of overheating under exessive full load)
The speed six is sometimes a miracle
Uwe
2. disconnect oil vapour pipe from air filter body
and keep engine running 3 min without pipe connected
before retesting!
Cylinder 1 is too high, i would recheck again
(with pressure loss test)
Cylinder 6 i would check throttle adjustment, if flow is low temp is also low.
(But it is better to keeep cyl 6 a bit down because of
danger of overheating under exessive full load)
The speed six is sometimes a miracle
Uwe
yzf1070 said:
Koen,
That does seem rather a high figure for cylinder one. To put it into imperial terms a difference of 65 psi. A difference of 15-20 psi or more between cylinders over all is generally considered to be an indication of the onset of wear and tear.
You mention that you found oil around the spark plug on 1, but you do not say if it was burnt oil (brown/black crusty deposits on the plug electrodes if you are burning enough oil the plug will smell acrid) or if it was liquid (unburnt) oil. If it was unburnt oil then this could be a reason for the higher compression. If there is enough oil and it is sitting on the piston rings it will improve the seal and the compression reading will be higher. You do not mention if you have to top up your oil tank very often. If you do then this would suggest that you have either worn rings or valve guides and from your brief I would suspect on cylinder one. The fact that the compression is so high on cylinder one I believe would suggest the rings are fine. My thoughts lead me to suspect the valve guides. I am not sure what tests can be done to disprove the guides are worn without removing the head. However having said all that, I would have expected that for such a volume of oil to be leaking into cylinder 1 to increase the compression...... I would have though the car would be blowing blue smoke out of the drivers side (yours is a left hooker?) rear tail pipe, or at least it will be very sooty black. Perhaps somebody else can add to this? Or correct the analysis? Does anyone know if an exhaust gas analyser reading can indicate burning oil? I am sorry but this is all I can offer with my limited knowledge.
Good luck
Hi,That does seem rather a high figure for cylinder one. To put it into imperial terms a difference of 65 psi. A difference of 15-20 psi or more between cylinders over all is generally considered to be an indication of the onset of wear and tear.
You mention that you found oil around the spark plug on 1, but you do not say if it was burnt oil (brown/black crusty deposits on the plug electrodes if you are burning enough oil the plug will smell acrid) or if it was liquid (unburnt) oil. If it was unburnt oil then this could be a reason for the higher compression. If there is enough oil and it is sitting on the piston rings it will improve the seal and the compression reading will be higher. You do not mention if you have to top up your oil tank very often. If you do then this would suggest that you have either worn rings or valve guides and from your brief I would suspect on cylinder one. The fact that the compression is so high on cylinder one I believe would suggest the rings are fine. My thoughts lead me to suspect the valve guides. I am not sure what tests can be done to disprove the guides are worn without removing the head. However having said all that, I would have expected that for such a volume of oil to be leaking into cylinder 1 to increase the compression...... I would have though the car would be blowing blue smoke out of the drivers side (yours is a left hooker?) rear tail pipe, or at least it will be very sooty black. Perhaps somebody else can add to this? Or correct the analysis? Does anyone know if an exhaust gas analyser reading can indicate burning oil? I am sorry but this is all I can offer with my limited knowledge.
Good luck
to answer your questions?
Don't know is it was burned or clear oil, it was told by the dealer. Will ask.
Yes, I top up the oil only when necessary and she didn't used that much oil. May be I overfilled it one time?
No obvious blue smoke out of the drivers side. (It's a LHD car sir, hmmm), only the exhaust sound/pressure is different; sort of on/off principle in comparison to the right; i.e. more regular
Last time the spark plugs where removed they looked burned.
Can't comment about the compression difference interval.
I hope I'm lucky
Koen
John Ravenscroft always said that a compression check on his engines was not a good way to test the condition of the engine due to the very high compression. We have always taken his advice and used a cylinder leakage test. My first thoughts would be that you have a tight tappet on the problem cylinder. That is assuming that ignition etc has been checked properly. The leak down test will confirm if you have a piston to cylinder wall or a head/valve problem.
Best of luck
Best of luck
scooterscot said:
John Ravenscroft always said that a compression check on his engines was not a good way to test the condition of the engine due to the very high compression. We have always taken his advice and used a cylinder leakage test. My first thoughts would be that you have a tight tappet on the problem cylinder. That is assuming that ignition etc has been checked properly. The leak down test will confirm if you have a piston to cylinder wall or a head/valve problem.
Best of luck
Leak test was OKBest of luck
engine out is dangerously close
koen
Gassing Station | Speed Six Engine | Top of Page | What's New | My Stuff