Poor running under acceleration

[scot850]

Are you sure they are melted together? They can be a bugger to separate if they have been together for a while. There is a clip and inside the joint there is a silicon seal which forms a vacuum making it hard to get apart. Try some silicon oil on the join and gently levering between the connector end and the coil. The coil is toast so don't worry about it, the harness is the thing to try and save. Harness may be still available but best to try to see if you can save it. Otherwise junkyard, here you come!

Often you may find coils at a junkyard too. New is nice, but you can often get a set of used for less than one new one. Check for cracks around the body of the coil and down the boot. The boots can also split helping them short out. Even if you have to pull 5 to get one good one it is worth it.

Neil.

[subzerocarfanatic]

I will try again, I have had them apart before. The plug itself has some of the melted plastic melted onto it.

[subzerocarfanatic]

OP said it has melted! I have never seen that before and can only suggest an internal short of some kind. I'd pull the spark plug and have a good look to see what it is like.

Did you replace any of the coil packs? Reason I ask is that I have heard of them shorting out. When I puled some out of a V70 I had a few years ago, they were full of cracks in their casings. One was causing a misfire. I ended up replacing them all, and cleaned the surface where the bolt for them goes through and connects to the head, and the head surface to make sure they were clean. This is the ground and again will cause a misfire if not clean and in good contact.

Misha is correct on the ECT. It is funny how a particular part can cause issues with these cars. It is like the spark plug wires for 98 and older can mostly be Bougicord brand. It must be down to how Volvo designed them to meet certain criteria and aftermarket ones don't manage to be consistent enough to hit the target every time.

For those who have been on this and other Volvo forums over many years we would be rich if we had the $1 for every time the ECT had become a problem due to failure or a bad connection at the plug or bad wiring at the rear of the power steering pump area. The ECT also controls the signal for the cooling fan so making sure this works is very important as these engines don't like being over heated.

Aftermarket parts from the OE manufacturer is generally fairly safe, but even there there are knock off parts packaged to look like brands like Bosch.

I know you have had a lot of challenges with this car, but you are now hopefully very close to a good running car!

Neil.

What would cause such a short, do I need to resolve this before installing the new coils,don't want to ruin a set of OEM Coils, or could the coils be the cause?

[subzerocarfanatic]

Here are some images of plug from cylinder 3. The plugs have less than 100 miles on them,probably around 50 miles or so since installed new,they are NGK Platinum,I did not gap them because they were specific for my make and model and i assumed they would be gaped accordingly.

[subzerocarfanatic]

I read on another post related to this same issue, to make sure the pre heater valve door is set for cool intake, how is this done and where exactly is it located, what does it look like,is it below the air filter housing somewhere and could this be a potential cause for the issue?

[scot850]

Turbos don't have one. Only NA's have the pre-heater pipework from the exhaust manifold to the air box. So not the issue on your car.

Check around the body of the coil for cracks in the plastic around and under the square section. Also check the boots for splits in them.

Finally was there any old engine oil down that spark plug recess, perhaps from an old failed oil filler cap seal. That could cause an issue.
It could just be an old coil having an internal short.

So all you can do is try to see if there are any shorts between the coil connector harness pins to try to eliminate any shorts there.

If you find no splits or cracks in either the coil or boot then that is all I can suggest unless you have a problem like in another thread with a leaking injector. Easiest way would be to sniff the oil on the dipstick and look for damp in the cylinder or on the spark plug.

Careful checking that type of plug for gap they are a little more fragile at the tips. Should still b 0.028" ideally, but sometimes get gapped to 0.030" out of the box which to me is a little wide.

Neil.

[subzerocarfanatic]

Ok, here are some images of the spark plug wells, plugs and the coils 1,2,4, and 5 starting with #1. Number 3 you seen already.
It is hard to see the top of piston,i will try with a light.Coil #1 and #2 are oily and wet but not melted, coil #4 and #5 are dry but #4 is melted by the plug just like #3 was.So it looks like coil 3 and 4 are both melted by the plug.
I am not sure if i am correct in actually numbering of each coil/cylinder but i numbered them 1 - 5 from left to right, picture 1 is first on left facing engine etc.

[subzerocarfanatic]

Here are the coils starting left to right facing engine, 1, 2, 4, 5.
1 and 2 are wet and oily, 4 and 5 are dry but 4 is melted by plug like # 3 from yesterday.