[Hans66]

Hi all,

was on my way home from work and about 5 minutes into the drive my 164 3.0 12V started popping into the exhaust and about one minute later started running on 5 cylinders only. There is no intermittance about this - it simply runs on 5 only, no matter what.
Had a look at the distributor and that looks used, but not damaged, listened to the injectors and they all sound good. Tried pulling the caps off and this didn't make an obvious diference to the way the engine runs.
What should I look into first, apart from changing the leads and plugs? Any type specific advice?

Thanks in advance,

Hans

 

[ChrisS]

Other than distributor cap and rotor arm being prime suspects, nope, just your normal stuff really. It's possible a plug well has filled with oil and the plug boot has allowed that into the HT area so of course, pull the plugs and check the HT leads while you are there. At least you don't have to remove anything else to do a plug job on a 12V.

I'm surprised you weren't able to determine which cylinder has failed by pulling HT leads though - it's normally pretty obvious when you pull a good one and make it worse?

Injectors - they are batch fired all at once, so if any aren't working, it's either a simple wiring fault or faulty injector, but the only proper way to test them is to put them on a test rig of some sort. Either a dangerous DIY effort or get them cleaned/tested perhaps. Typically about £15 each. If you are feeling brave (or perhaps that should be stupid), pull the fuel rail and injectors leaving injectors attached to rail, invert it so the injectors are pointing skywards, remove the LT to the coil then crank it.... Potentially a very hazardous exercise though. Safer methods will involve making up your own test rig with an HP fuel pump etc.

While the plugs are out, do a compression check as well. Depending on engine condition and spec, you are looking for somewhere around 190psi or better but also important, good matching across cylinders.

Cam timing rarely jumps on the 12V but it can happen. Unless it's really bad, it would still run on all cylinders but you'd get a loss of power and an 'odd' sound to it - almost like it's missing. Cam timing is easily checked using the excellent cam timing template that was kindly created and uploaded to the interweb many years back by an Alfisti from the US. With the template, you only need to remove the plastic cam centre covers at the front of the engine belt cover and the plastic blanking plug in the bellhousing (assuming it's not already gone AWOL). No need to pull the top covers etc off and it;s more accurate than using the marks on the camshaft bearing caps anyway.

Yell if you want a copy of the template.

 

[Hans66]

Thanks Chris, I'm reasonably confident that the cambelt hasn't jumped, the signs of that are usually pretty obvious. This has all the symptoms of running on 5 cylinders, including the typical 5 cylinder "offbeat sound". Like an Audi or VW product
I've only VERY recently returned to Alfa ownership but I've owned an Alfetta GTV and a 75 in the past, so the Busso is somewhat familiar (although that was a long time ago).
While the 164 is no 75 or GTV, it will have to do, as prices for the former two are now a bit too high, at least here, in New Zealand.

Also, I'm going to discount the injectors being at fault for the time being, as I'm pretty sure I can smell unburnt fuel in the exhaust now...

 

[sprint_veloce]

Whenever this happened to my 12V, it was always a duff plug. But then I always ran them until one failed, somewhere around 20-30k miles usually.

 

[Hans66]

I'd hope you're right. I have just bought this one, so I can't really discount that. There is one good thing about this car though.... ALL the electrics work...up to and including the heated seats. Now there's something I haven't seen before.

 

[ChrisS]

Don't be too quick to dismiss a jumped cam. I had a 12v motor where the marks on the cam caps on the rear bank were wrong....so when I timed it, it was wrong by a tooth. It took a long time to spot and I only confirmed it by measuring lift on overlap......and then found the timing template that uses the scribe marks on the cam pulley centres, which confirmed it. That engine ran OK but was down on power, pinked and sounded 'odd'


...but, it does sound more like a plug failing on yours.

 

[Avocet]

If you can get somewhere really dark, fire it up and with it idling, just spray a fine mist of water over the HT electrics with one of those plant squirting bottles gardeners use. Look for tiny little blue flashes, suggesting that there's an HT component breaking down somewhere.

 

[Hans66]

Thanks for the excellent advice everyone. New plugs and leads are turning up tomorrow, so I should have some sort of outcome by the end of the week. On a positive note, I have found the original tools in the boot of the car, including the spark plug tool. That should make changing them fairly easy.

 

[Hans66]

Well, it was a failed plug. Case closed. Also I washed the car and the speedo stopped working. Ah, the joys of Alfa ownership.