DB9 idle - question
Discussion
Hello everybody, I hope somebody of you might be able to help me answering this question - I must admit that I do have two left hands and usually have my car looked after by the nearby AM dealer. But, due to the current situation, asking them is not an option.
My 2004 DB9 is running well and without any noticeable faults, but when I put the 'box in "P", the idle revs are slowly moving up and down, between 800-900 rpm. When in "N" or "D", idle is a steady 700, without "pulsing".
What could that be? No other indicators, e.g. misfire, stalling etc.
It would be great if somebody could help, even along the lines of "they all do that".
Thank you!
My 2004 DB9 is running well and without any noticeable faults, but when I put the 'box in "P", the idle revs are slowly moving up and down, between 800-900 rpm. When in "N" or "D", idle is a steady 700, without "pulsing".
What could that be? No other indicators, e.g. misfire, stalling etc.
It would be great if somebody could help, even along the lines of "they all do that".
Thank you!
RMDB9 said:
Just to reiterate - it only happens in "P" but not in "N" - but both count as "idle", right?
Today i tried it again. The "oscillation" is really not big, I would say 50 rpm give or take.
When in P and it happens can you feel the car shaking (very mildly) from side to side ? That is classic coil induced misfire.Today i tried it again. The "oscillation" is really not big, I would say 50 rpm give or take.
In D there is drag on the torque converter and you may not notice it. I would expect it also to be noticeable in N, but am no expert.
Can you ascertain when the coils/ plugs were last replaced ? That is the most likely culprit and would be worth doing anyway unless you know for sure they have recently been seen to.
The other thing to do is find a bit of open road, change down and floor it. If the coils are on the way out you should get an "emissions warning"
I have a 2005 DB9 and had a similar misfire at 35k miles. new coils and plugs sorted it.
Edited by pschlute on Friday 24th April 19:52
Edited by pschlute on Friday 24th April 19:54
Edited by pschlute on Friday 24th April 19:56
Not much point in asking in this forum... very few ever seem to bother...
But... lll put my opinion in.
Don’t worry at all about the coil packs. You only need to consider them if you get the engine light and emissions message come up on dash. I bought new stock of the coil packs from an one manufacturer instead of Aston. £200 I paid.
I fitted them myself. It’s a six hour job.
Don’t bother with any minor issues with revs unless you get an engine light flash up. Then, and only hen, get new coils and plugs.
Steve (with the 126000 mile db9)
But... lll put my opinion in.
Don’t worry at all about the coil packs. You only need to consider them if you get the engine light and emissions message come up on dash. I bought new stock of the coil packs from an one manufacturer instead of Aston. £200 I paid.
I fitted them myself. It’s a six hour job.
Don’t bother with any minor issues with revs unless you get an engine light flash up. Then, and only hen, get new coils and plugs.
Steve (with the 126000 mile db9)
All these horror stories... if it’s a misfire, the sensitive diagnostics on board will show up the ‘emissions service required’ notice on the dash. I used mine for a month before changing the coils. The cat didn’t eat anything and the engine is just the same. It’s bulletproof. No one disables it either... why would they.?
When mine misfired I got no EML or emissions warning. Turned out PO had replaced the battery and didn’t relearn the misfire parameters. After I did the run down procedure to reset these, the dash lit up immediately with all the warnings. New coils & plugs fixed it, easy enough to do at home. This at 15500 miles on a 2005!
On other cars coil packs are not a normal service item but I see lots of references to changing coil packs on DB9s and Vantages. Almost as if people change them all when changing to long life spark plugs. Why is this?
I had an Alfa Romeo 164 Cloverleaf 24V which started an occasional miss fire under high load. The garage traced the problem to 1 of the 6 cop type bosch coils and changed just that one. There were never any problems from the others.
I had an Alfa Romeo 164 Cloverleaf 24V which started an occasional miss fire under high load. The garage traced the problem to 1 of the 6 cop type bosch coils and changed just that one. There were never any problems from the others.
MGDavid said:
On other cars coil packs are not a normal service item but I see lots of references to changing coil packs on DB9s and Vantages. Almost as if people change them all when changing to long life spark plugs. Why is this?
I had an Alfa Romeo 164 Cloverleaf 24V which started an occasional miss fire under high load. The garage traced the problem to 1 of the 6 cop type bosch coils and changed just that one. There were never any problems from the others.
I can think of two reasons. One, On a DB9, plugs and coils are so deeply buried - manifolds and engine bay braces have to be removed - that the price of coils compared to the time and labor investment is relatively small. There may also be a price incentive to buy multiple coils. I once replaced some on a Ford pickup and a full set of eight was only about twice the price of a single coil. I had an Alfa Romeo 164 Cloverleaf 24V which started an occasional miss fire under high load. The garage traced the problem to 1 of the 6 cop type bosch coils and changed just that one. There were never any problems from the others.
MGDavid said:
On other cars coil packs are not a normal service item
Other cars perhaps do not have the coil packs buried deep in the v of a 12 cylinder 6 litre engine. They get subjected to enormous heat and have a lifespan of approx 40k miles because of this.Replacing one coil pack involves removing the exhaust manifolds and gaskets. It is an expensive procedure. Replacing the other 11 packs at the same time makes a lot of sense.
K33LER said:
All these horror stories... if it’s a misfire, the sensitive diagnostics on board will show up the ‘emissions service required’ notice on the dash. I used mine for a month before changing the coils. The cat didn’t eat anything and the engine is just the same. It’s bulletproof. No one disables it either... why would they.?
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