Testing Coil packs; 1999 S70

MikesS70 · Post by **MikesS70** » 11 May 2009, 11:52

I'd go ahead and do the the same thing with cylinders 1, 3, and 4 just to confirm.

Also, I'd swap coil pack #5 to a different cylinder and retest to confirm. Cylinder #5 should light up OK.[/quote]

I second the swap suggestion. These coilpacks aren't too cheap. A dead fuel injector would cause the same symptoms. Swapping the coilpacks lets you verify it is really the cause, and it is farely easy to do.

-Bruce[/quote]

Okay ...a fresh start after lunch. Reinstalled the plugs and coil packs. Running situation still the same. Rough and what sounds like a cylinder miss. Engine will idle rough but stable ...about 1000 rpm. Exhaust smell has unburned fuel odor.

Removing the coil wire from #5 pack causes no change in idle quality.

Removing coil wires, one per each run cycle, causes a decrease in running idle quality although not as much of a decrease as I might've guessed (car is apparently running on 3 cylinders) . Test: #5 Connected, #4 disconnected ran engine
#5 Connected, #3 disconnected ran engine
...etc.

Having #5 disconnected and redoing this test resulted in the same findings.

Swapping #5 and #2 coil pack positions caused no change in the idle quality experienced when #5 was in its original position.

I don't have an inductive tester; tried using my inductive timing light but with no wires to wrap the coil around it did not work.

There is the possibility the coil is still good but the rubber boot is leaking voltage to the cylinder head ...the rubber is well-baked, still pliable but charred a brown color.

FCP and IPD sell the OEM Bosch coils for about $50 a piece ...not too bad in my book when I've seen what some of the other stuff needed for the care and feeding of a Volvo sells for ...almost like Volvo goes out of its way to uniquely design stuff so it costs more ...or so you have to bring it to the dealer.

I'm still leaning toward a bad coil pack, especially with the lack of change in idle quality when it's disconnected. The heavy, unburned fuel smell would seem to indicate the injector in that cylinder is firing. Also the plug looked the cleanest of the five when I removed them. The lack of a radical change in idle quality (like I was anticipating) with the disconnect of #5 and a second pack could be attributed to the engine computer compensating and the general good balance and build of the engine itself....

Mike

Post by **vegasjetskier** » 11 May 2009, 16:16

MikesS70 wrote: Swapping #5 and #2 coil pack positions caused no change in the idle quality experienced when #5 was in its original position.

So you moved #5 coil pack to cylinder #2 and then you disconnected the #2 coil pack (now in cylinder #5) and the engine reacted the same as when the #5 pack was in cylinder #5? If so, the problem is not the coil pack.

MikesS70 · Post by **MikesS70** » 11 May 2009, 18:16

vegasjetskier wrote:
MikesS70 wrote: Swapping #5 and #2 coil pack positions caused no change in the idle quality experienced when #5 was in its original position.
So you moved #5 coil pack to cylinder #2 and then you disconnected the #2 coil pack (now in cylinder #5) and the engine reacted the same as when the #5 pack was in cylinder #5? If so, the problem is not the coil pack.

No ...what I did was swap #5 and #2 packs and connect them to the ignition harness ...the #5 pack was now connected to the #2 ignition harness plug and #2 pack was connected to the #5 ignition harness plug. When the engine was started it ran the same as before the coil packs were swapped. If #5 is in fact bad, like I suspect, then moving it around simply means the motor will run on a different set of 4 cylinders ....and the rough idle quality should stay the same. The fact it did not have a rougher idle with the packs swapped says to me I can probably eliminate the ignition wiring harness and its connecting plug ...spark plug #5 is now firing but #2 is not.

Maybe I'm missing something but it seems to me that unless you have a good pack to swap out for the suspect pack or there is a specific way to test the pack (using a VOM meter for example) you'll really never know for sure if the pack's gone bad or there's something else with the #5 cylinder (electrical connector, fuel injector).

Given the obvious odor of unburned fuel coming out the tailpipe, the physical condition of the pack when I removed it, how the condition came about (very sudden) plus the slight degradation in the idle quality when a second coil pack is disconnected, I feel pretty confident in pursuing a new coil pack.

Barring that I could see where an injector may be stuck open running too much fuel and creating a very rich mixture in #5 cylinder ...but without the high-zoot Volvo test equipment it's all just an educated guess. If the new pack does not fix the problem then I will look at the injector.

In the end, I'll hopefully learn something out of it all and save myself some money in the process.

Post by **vegasjetskier** » 11 May 2009, 18:55

MikesS70 wrote:
vegasjetskier wrote:
MikesS70 wrote: Swapping #5 and #2 coil pack positions caused no change in the idle quality experienced when #5 was in its original position.
So you moved #5 coil pack to cylinder #2 and then you disconnected the #2 coil pack (now in cylinder #5) and the engine reacted the same as when the #5 pack was in cylinder #5? If so, the problem is not the coil pack.
No ...what I did was swap #5 and #2 packs and connect them to the ignition harness ...the #5 pack was now connected to the #2 ignition harness plug and #2 pack was connected to the #5 ignition harness plug. When the engine was started it ran the same as before the coil packs were swapped. If #5 is in fact bad, like I suspect, then moving it around simply means the motor will run on a different set of 4 cylinders ....and the rough idle quality should stay the same. The fact it did not have a rougher idle with the packs swapped says to me I can probably eliminate the ignition wiring harness and its connecting plug ...spark plug #5 is now firing but #2 is not.

Maybe I'm missing something but it seems to me that unless you have a good pack to swap out for the suspect pack or there is a specific way to test the pack (using a VOM meter for example) you'll really never know for sure if the pack's gone bad or there's something else with the #5 cylinder (electrical connector, fuel injector).

Given the obvious odor of unburned fuel coming out the tailpipe, the physical condition of the pack when I removed it, how the condition came about (very sudden) plus the slight degradation in the idle quality when a second coil pack is disconnected, I feel pretty confident in pursuing a new coil pack.

Barring that I could see where an injector may be stuck open running too much fuel and creating a very rich mixture in #5 cylinder ...but without the high-zoot Volvo test equipment it's all just an educated guess. If the new pack does not fix the problem then I will look at the injector.

In the end, I'll hopefully learn something out of it all and save myself some money in the process.

Well I suggest doing this and see what happens: Move #5 coil pack to cylinder #2 and then disconnect the #2 coil pack (now in cylinder #5). If the idle becomes worse as in your first test, you know that the burned coil pack is bad (because #5 cylinder was firing with the #2 pack connected, but then didn't when the #2 pack was disconnected). However, if the idle stays the same, you know that something else is wrong with cylinder #5 (because #5 cylinder isn't firing even with the #2 coil pack in it).

The fact that the spark plug lost its electrodes concerns me. That must have taken a lot of heat. Maybe a lean mixture from a faulty or plugged injector? Can you post a pick of that spark plug?

MikesS70 · Post by **MikesS70** » 11 May 2009, 21:05

Well I suggest doing this and see what happens: Move #5 coil pack to cylinder #2 and then disconnect the #2 coil pack (now in cylinder #5). If the idle becomes worse as in your first test, you know that the burned coil pack is bad (because #5 cylinder was firing with the #2 pack connected, but then didn't when the #2 pack was disconnected). However, if the idle stays the same, you know that something else is wrong with cylinder #5 (because #5 cylinder isn't firing even with the #2 coil pack in it).

The fact that the spark plug lost its electrodes concerns me. That must have taken a lot of heat. Maybe a lean mixture from a faulty or plugged injector? Can you post a pick of that spark plug?[/quote]

Will give it a go tomorrow. The plug had begun to back itself out of the cylinder head ...when I discovered it the plug was finger loose and the inside of the plug reccess was coated in sooty carbon ...the screw-on top of the Bosch plug was cracked in two pieces. When I first removed the spark plug access cover I saw the #5 coil pack covered in a light coating of soot; combustion gases were blowing up from around the loose plug, up around the spark plug boot and blowing out from around the coil pack boot into the wiring harness area. It's difficult to know whether the prongs broke off all at once or over a period of time and when the last one went, the plug quit working.

The plug itself doesn't look melted or overheated, the electrode and ceramic surround are a dark grey color and match the other plugs. I can only gues that maybe the vibrations set up as the plug "rattled" loose in its threads caused the prongs to break off. The prongs don't look very substantial when compared to a normal single prong plug. I'll see if I can get a pic posted of the set and the busted plug.

MikesS70 · Post by **MikesS70** » 16 May 2009, 15:44

An update on my progress so far. I've been out of town for the last 4 days so I've not been able to work on the car.

I went ahead and ordered a coil pack from iPd ...great website and quick delivery using the USPS Priority Mail option ...I thought the OEM Bosch part was probably going to be made in Mexico or Brazil but to my surprise was of German manufacture ...very impressed.

As part of the oil change I did just prior to this disaster, I cleaned the MAF and gave the throttle body a scrub. The car ran fine after the oil change ....the #5 plug still being able to fire.

I installed the new pack but apparently I'm not gonna get off easy on this ....the car still runs exactly as it did before ...very rough and acting like it's runnning on less than all five cylinders.

I checked the wiring harness near the No. 5 plug for burns or damaged wiring but everything looks fine ...nothing showing any heat related damage, wire cuts, breaks etc.

I'm at a loss now as to what to do ....my generic OBD II reader shows two codes locked in the computer: P1026 and P1031.

My only other thought is to remove the injector rail and examine the injectors for signs of dirt or clogging ...my wife tends to buy gas at the local Kroger ....

Any suggestions would be greatly welcomed .....

Thanks

Mike

Post by **vegasjetskier** » 16 May 2009, 15:54

I don't know how much work it would be, but you could try switching the #5 injector for another cylinder and see if your dead cylinder moves. If so, you know that injector is bad.

MikesS70 · Post by **MikesS70** » 16 May 2009, 18:16

vegasjetskier wrote:I don't know how much work it would be, but you could try switching the #5 injector for another cylinder and see if your dead cylinder moves. If so, you know that injector is bad.

From appearnces it *looks* like dealing with the injectors is pretty straight forward ...they are all right there under the fuel rail just hanging in the breeze so to speak ...and the rail is held to the intake manifold with two bolts. I have a Haynes manual that covers up to '98 and the injector setup looks the same ...procedures look pretty simple. Don't know what I'll find but I can't think of anything reasonable that would cause such a rough running motor.

Mike

Post by **vegasjetskier** » 16 May 2009, 19:01

S70FuelInjectorsReplacing1999.pdf: (53.09 KiB) Downloaded 374 times

MikesS70 · Post by **MikesS70** » 18 May 2009, 18:16

Culmination of this saga ...it's not a coil pack, it's not a bum injector ...it's the evil ETM rearing its ugly head yet again. In all my scrounging of the forums here (especially Don's ETM Room) nothing was ever mentioned about a very rough idle (like it's running on 4 cylinders). But ...a rough idle is in fact a common malady with a failing ETM.

I found the ex-Volvo dealer (now a Subie dealer) still works on Volvos and can do everything (including software downloads) except factory warranty work. I managed to get the car over there and explained my symptoms and the converted OBDII codes (to volvo DTC's). He said straight away, 99% sure, it was the ETM failing. I asked about the rough idle and told him about my coil pack; he said the rough idle is typical of the ETM failure. He explained that the ECM and ETM have essentially lost communication with one another; the ECM does not know what the throttle is doing and so comes up with some wacked out fuel schedule to feed the injectors ...ergo the rough idle.

The car will undergo a diagnostic tomorrow and hopefully get this squared away ...the timing belt is also scheduled to get replaced. If I'm lucky, the in-service date will fall within the 10year warranty period and this will be a "free" fix.

Mike