Electrics: 850: Ignition Coil

[volvo2]

1994, Volvo 850, 200k miles

How long does the ignition coil last? Anyone replaced theirs?

I sometimes have difficulty starting and wonder if it could be the coil. Have already replaced distributor parts and cables.

[Nick850GLT]

Interested to know if you have got anywhere with this?
I have the same car - also in Worcestershire (Malvern) - with 250k on the clock. The engine has just started to run a bit rough - juddering a bit a low revs.
Initial diagnosis was a random misfire, so I replaced leads, plugs, rotor arm and distributor cap - all to no effect. Back to wondering if the coil might be in partial failure.
Various folk have suggested air leaks - but I can't find anything.

[PSJVTHEBEST]

Mine had similar issues at the end of a long drawn out component replacement process (I know that's not the most efficient way of going about fault diagnosis btw) but it turned out to be the crankshaft position sensor. But I had cleaned and replaced virtually everything before that! Idle control valve may be worth a clean too - easy and cheap!

[Clan]

Originally Posted by volvo2

1994, Volvo 850, 200k miles

How long does the ignition coil last? Anyone replaced theirs?

I sometimes have difficulty starting and wonder if it could be the coil. Have already replaced distributor parts and cables.

Never known one fail yet. they are the highest Bosch quality.

[Luxobarge]

Originally Posted by Clan

Never known one fail yet. they are the highest Bosch quality.

Seconded.

[Nick850GLT]

Many thanks PSJVTHEBEST - probably worth a try for about £30 - that won't get me far on a garage bill to find the problem!

[SteveSarre]

For me, I have found that the engine "hunts" (alternately speeds up and slows down), when at idle, when the Idle air control valve is bad.

When the IACV is bad, the internal cylinder jams and will not rotate. Don't force it. You can try cleaning with carb cleaner.

A good candidate for a poor idling is the small rubber elbow under the end of the intake manifold furthest from the battery. They tend to split.
You can replace it yourself without removing the intake manifold if you have some curved forceps or needle nose pliers. The elbow itself is cheap.

If you have replaced plugs did you use the right Volvo brand and model (turbo plugs differ from non turbo)? If you have replaced leads, did you replace the sixth lead that goes to the coil? I think it is called the Queen lead.

If searching for a leak, then spraying brake cleaner around can sometimes pinpoint the location.

Hope that helps,
Steve

[SteveSarre]

PS
If you pull off the leads one at a time when idling, you may find that one cylinder is not doing any work , which you can then investigate.

[Nick850GLT]

Thanks for those comments.
I have a misfire, but I don't think it is on a consistent cylinder.
I have just replaced plug leads (including the master), distributor cap and rotor arm, and swapped in a different set of the correct Volvo plugs - none of this made any difference. I've also examined all the air pipes pretty carefully and can't see any sign of problems.
As far as I understand, the IACV might cause random idle speed variation, but perhaps not the misfire.
From PSJVTHEBEST's comment, it still seems like the CPS sensor would be worth a shot.

[PSJVTHEBEST]

I had read that both camshaft position and crankshaft position sensors play up and can display the symptoms you're experiencing but, as I said, the crankshaft one was the culprit in my case although the camshaft one is easier to change!