DB7 Coil Pack Replacement:
Carried out and documented by me in 2016. Brendan Cunningham.
Before you start:
You need to have:
Suitable range torque wrench/wrenches.
¼” drive set capable of off-axis operation.
Combination spanners down to 7mm.
Good quality single hex spark plug socket and suitable drive.
Also helpful would be decent 3/8” drive set with flexible ratchet (very useful for undoing EGR bolts).
You need to be capable of:
Spending hours hunched over the engine bay.
Being familiar with handling tools and mechanical components.
Getting your fingers into very tight spaces and winding on and off very small nuts and bolts without dropping them or small spanners used, etc.
You need to be aware of and able to deal with:
The chance a bolt or stud may shear off (happened to me on the inlet manifold).
Electrical connectors may be brittle and break.
The requirement for absolute cleanliness in dealing with the fuel and intake system.
The possibility of petrol spraying everywhere if the high pressure fuel rail assemblies aren’t assembled correctly.
Parts you must have:
12X New coil packs
12X New spark plugs
Parts you may need to have ready:
2X Inlet manifold gaskets
2X EGR valve gaskets
2X IAC gaskets
Remember, if you get half way, get stuck and can’t rebuild back to running order you may not be able to drive your car to a garage to fix it for you.
This all sounds a bit doom and gloom, however, this is one of those jobs that wasn’t actually as hard I thought it would be, but does have a number of potential pitfalls which could catch out the less experienced/confident.
Tip: Stuff paper towels below where you are about to undo nuts and bolts. This
way, if you drop one and everyone drops at least one, they will not go far
and can be retrieved.
1. Disconnect the battery.
Loosen negative clamp on battery, but don’t remove.
Turn on ignition, turn off and disconnect battery within 10 seconds to avoid triggering the alarm.
2. Throttle assembly.
Unclip the left and right throttle cables, label and store. Be careful not to lose the spring clips on the outboard ends of these cables.
Remove the 4x 8mm nuts and washers holding the throttle tower.
The throttle tower can be swung out of the way and placed in front of the radiator without further dismantling or disconnecting the remaining throttle cable.
3. Injector wiring.
Carefully unclip the injector connectors (beware brittle parts) and move the harnesses aside to aid access. In my case it was obvious which was left and right, but you may wish to label.
4. Fuel rail supply.
RELEASE FUEL PRESSURE in the system by undoing the schraeder valves and depressing the valve centre pin. Shroud with paper towels as a short squirt of fuel will result.
Slightly back off the 7mm head bolts securing the fuel rails (back of engine), but don’t undo fully yet.
Remove the 6 bolts securing the fuel rails to the manifolds.
Carefully, lift fuel rails off injectors. Petrol will spill.
Keeping everything clean and free from dirt ingress now gets very important.
With the fuel rails loose, you can now lift them up to get better access to remove the small 7mm head bolts attaching the fuel rails to the supply. Stuff paper towel below and around to catch the petrol which will flow out in alarming amounts.
Check the blue O rings on the injectors and rails. These are usually fine unless damaged and won’t need replacing. Store everything carefully.
Sections 5-20 are the same for left and right banks.
5. IAC solenoid removal.
Undo and remove. Remove the wiring connector. The inner bolt will need wriggling to clear the manifold – it should come out, just. The IAC gasket may be fine or may tear and need replacing. I refitted with a slightly shorter bolt for the inner side.
6. Down behind where the IAC came from you will see the stud with the extra small 8mm head nut to hold the harness. Undo and remove the nut and stud. These need removing as the studs are threaded into the manifold and it won’t come off otherwise.
7. Undo the jubilee clip fixing the air intake duct.
8. Undo the other wiring connector (behind) from the throttle position sensor.
9. Working back, prise off the three vacuum hoses.
10. Remove the 8mm head nuts from the EVR solenoid and move the unit aside to gain access below.
11. Remove the nut and stud as in “6”.
12. Difficult. Remove the bolt further back securing the rear of the same bracket (engine lift mount doesn’t help).
Unbolt the EGR valve (10mm head bolts). I used deep 3/8” socket
and a flexible ratchet drive.
The bolts are long and in my case tight, so be careful to keep everything square as you do NOT want to round off those relatively small 10mm heads!
The valve won’t move once undone.
14. Unbolt the inlet manifold. Do this carefully. I suggest you give each
nut a series of healthy taps first before loosening. I undid the bolts in the
same sequence as tightening 1 (front), 7, 3, 2, 6, 4, 5.
If any bolts feel “wrong” as you back them off, don’t force them. Squirt a lot of release oil around the base of the bolt where it sits in the cylinder head and wait 24 hrs. Despite my best efforts one bolt sheared and I had to drill it out and helicoil it. It’s now better than new, but this is not for the beginner as very accurate drilling is required.
15. You are now ready to remove the manifold.
Lift slightly at the inboard side to break any gasket seal (usually no issue) by the inlets, then slide forward to clear the EGR valve. The manifold should now lift clear.
Debris will inevitably fall down onto the valves, so plug the inlets with paper towels immediately to stop any more objects going where they could wreak havoc.
16. Lift off the gasket. Mine were so good that I reused them, as after 14 years and 40,000 miles they showed no signs of deterioration at all. Their function is simply to maintain an airtight seal at moderate vacuum, so not like head gaskets. You make your own judgement here, but if unsure, fit new ones.
17. Undo the small torx head machine screws holding the cover plate and store. These are small and break easily, so be careful here. Remove the cover plate to finally reveal your goal!
18. Gently lift each coil pack slightly out of its recess. This allows some
wriggle room and makes unclipping and removing the wiring connectors easier
with less force. Note how the coil packs sit for reassembly.
Very gently unclip and remove the connectors (their brittleness after time is well documented).
Pull the harness aside as you go.
19. Pull out the coil packs (mine looked new, so don’t mix up with the expensive new ones you have just bought!).
20. Using a good single hex dedicated plug socket and taking great care to
keep the extension and force on axis undo the and remove the plugs.
This is the whole process in reverse, but please note:
Torques: Plugs 16-20 NM , Manifold 8-12 NM , Fuel rails to manifold 8-12 NM
Debris will have fallen down the inlet tracts. Make up a small tube attachment to a powerful vacuum cleaner and thoroughly clean all around the valves – particularly around the seats. Use a powerful torch to check.
As several of the 14 inlet manifold bolts showed some evidence of corrosion and were tighter than expected, consider replacing them (air can get at these as the threaded holes aren’t blind). AML wanted about £140 for the set. The local engineering factors sold me top quality high torque items for £4.50 for the set. No further comment needed.
Smear clean oil around the blue fuel rail O rings to ease reassembly as you definitely do not want these to sit incorrectly!
Remember, given the tiny size of the four nozzles in the injectors, you must keep everything super clean.
Triple check the fuel rail connections before turning on the ignition as this is the point that the system will re-pressurise and fuel leaks could occur.
In my case, the engine started on the button and sounded sweet and smooth.
Time to feel smug.