Troubleshooting a dropped cylinder

The problem: Occasionally my six cylinders in the Stagea will drop down to five with no prior warning leaving me with a shaking engine and a sound like an ill WRX. This comes and goes randomly but usually occurs at low speeds. For a while I’ve suspected the coil packs were at fault but after some reading I’m not too sure. So yesterday it was a half day in the garage for some fine tuning and hopefully a solution…

Possible dropped cylinder culprit #1: The MAF sensor

Now there’s two parts of the MAF sensor that could be causing some dramas here – one is the sensor wire that may need a clean to get anything caked on the wire off and the second is old cold solder points that could be causing some problems by not doing what it should. So I attended to both. For the wire I used a proper MAF sensor cleaner (amazing how you can’t buy this stuff in a smaller bottle for such a small wire..) and let it dry before bolting it back to the air box.

For the electrics side of the MAF I broke out my soldering iron (and it brought back so many memories of doing the same thing to patch up various electronics in my old RX7) and re-soldered all the points while also cleaning up some slight corrosion that had been building up in there. Getting to the pcb is super easy as you just cut away the rubber trim, peel back the lid and lift up the metal plate.

(Seriously the Duratech soldering iron I bought years ago has well and truly paid for itself many times over!)

I suspect that this is the original factory unit which means it’s now 17 years old. A bit of soldering work should hopefully get it behaving like it should.

 

The metal lift up plate under the rubber lid.

 

Thankfully not too many points to desolder and then resolder.

The sensor cleaner I used was Liqui Moly Air Flow Sensor Cleaner but this one should work just as well.

Possible dropped cylinder culprit #2: Spark plugs

Pulling all six didn’t reveal much – none of them were caked in oil or black with carbon. However it did give me an opportunity to gap them all down from 1.1mm to .8mm. Apparently this helps when you have coil pack dramas going on (which I do). So while they were out, out came the feeler gauge and down they went. I’m sure the packs are still going to spark and trigger a warning (yep, they do!) but as long as all six cylinders run then I’ll be happy)

Removing all the stuff to get to the spark plugs (and coil packs) makes me yearn for the days of my Soarer with it’s 1JZ-GTE and ease of plug and pack access…)

 Possibly not a dropped cylinder culprit, but since it’s out: The air filter

It’s fair to say that it’s seen many a dusty road in it’s time and desperately needed a bath. So after a degreaser soaking, it coughed up more than a lungful:

Yes the filter is in there somewhere…

Ahh there you are!

After letting it dry out on the line for a few hours, it was re-oiled and ready to help Warwagon breathe again!

So how did I go?

In the short ten minute test drive after I bolted everything back together, all seemed to go well. However today’s drive to work and back (70kms) will be the ultimate workout for it – wish me luck!

EDIT: One day later. Erm, no. Random vibration and engine shake still there. Have started swapping out coilpacks in the hope that one of them is causing the dramas.

EDIT: Two days later. I might have accidentally stumbled over the answer as it looks to be the coil packs which I initially ruled out. Over the past few days I’ve been cycling though my coil pack collection, replacing one each day. Today I had a very smooth run into work and a mostly trouble free ride home. Halfway through both trips I got the coil pack warning lights on the dash and a slight hesitation for a few moments, but nothing like the massive vibrations I’ve been experiencing before. So they still spark, but the one that was well and truly causing some of my hassles seems to have now exited the line up. Phew.

(And also I don’t know if this has helped any but I did it anyway – when swapping one of the coils out and putting one of my spares in, I covered the base above where the rubber boot sits with a decent layer of Permatex gasket maker, just to help seal up things that should remain sealed. Normally I’d use a high temp silicone but with none on hand this was the next best thing and it could have possibly assisted to keeping the spark aimed where it should.)

Right, now to save up for a new set of coil packs..

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