3.0 Help Please

[V AR 164]

Hi all,

......

Last night I was on the freeway cruising home when I noticed the car developed a missfire. At first I thought nothing of it because it has happened a few times before.

But, usually it would disappear after a few more mins of driving but this one persisted.

So got it home and went out today to figure out if I could fix it.

Pulled the spark plugs out and to my surprise, the rear middle cylinders plug was completely destroyed with what I can only describe as build up.

All others were fine except this one. So I went out and bought a new set, put them in and the missfire continued.

I have now noticed it blows white smoke and when I pulled out the new middle rear plug, it was a bit oily.

I'm going to borrow a compression tester tomorrow to most likely confirm my suspicion that it is a piston ring that has destroyed itself.

Can these parts be bought and would it require the motor to be pulled out?

Still trying to hope that it's not serious :/



Andrew.

[poohbah]

I don't know if this helps Andrew. Fingers crossed its not a major engine out job required.

Top right might apply - sandy coloured deposits. (Straight out of my GTV Haynes manual).

And also top left in the bottom pic, given the new plug came out oily. Both pics suggest worn valve guides maybe?

[Citroënbender]

I'd see that as more likely a head gasket issue. Looks a bit like crystallised antifreeze.

[V AR 164]

Thanks for the replies,

Poohbah that does indeed help, maybe it could just be a worn valve stem seal letting oil into the cylinder and not sealing properly, causing it not to ignite the fuel/air mix properly.

Citroenbender that could also be very possible. I have had a look in the coolant overflow tank and haven't seen any oil residue though and likewise with coolant in the oil.

Going to take it to my mechanic tomorrow and will let you guys know on the outcome.

Cheers, Andrew.

[bteoh]

I have a 1991 164 12v and I am having a similiar issue with no 2 cylinder but mine was just very oily. I measured the resistance on the no 2 spark plug cable and it was registering about 4400 ohms. Apparently it should be around 2500 ohm. I am changing the spark plug well seals as there was also a bit of oil in the spark plug well. Previously, I was using NGK BP6E plugs. Have just got a set of B5ES and will try that. Hopefully it might fix the miss-fire issue.
Cheers

[poohbah]

Andrew, further to Brian's suggestion re spark plug seals:

[V AR 164]

Thanks guys,

Well some good and bad news.

Firstly I did a compression test today, and I was actually pretty pleased with the results. All cylinders measured dead on 150psi EXCEPT the one with the missfire.

The test showed 0psi 

I bought a usb inspection camera and had a look into the cylinder which revealed a piston in very good condition with no 'scratch' marks on the cylinder wall.

I then put oil into the cylinder and re-tested it. Again I got a reading of 0psi. Thank God!!!

This (should) mean the piston rings are still in good condition, however the valves are not so happy.

Going to bring it over to my mechanic to fix it, hopefully it is just a valve that went bad or the stem seals. Going to replace all the stem seals while I'm at it too. Also, should I drive it the 5 min trip or book a tow truck?

I'll keep you all posted.

Cheers, Andrew.

[V AR 164]

I have a 1991 164 12v and I am having a similiar issue with no 2 cylinder but mine was just very oily. I measured the resistance on the no 2 spark plug cable and it was registering about 4400 ohms. Apparently it should be around 2500 ohm. I am changing the spark plug well seals as there was also a bit of oil in the spark plug well. Previously, I was using NGK BP6E plugs. Have just got a set of B5ES and will try that. Hopefully it might fix the miss-fire issue.
Cheers

I highly recommend you check the coolant temperature sensor. I had a missfire issue that I was battling for months until I changed the connector and all my issues were solved. I replaced mine with a BOSCH EV1 Injector Connector and it fixed it.

Andrew

[Citroënbender]

I'd drive it, provided a torch down the plug hole shows no debris or impact damage.

Also, quite possibly I'd be looking for an in-situ repair if the motor and subframe have never been out. Although it's a bit more fiddly in some ways, you'll disturb less peripheral stuff.

[poohbah]

Andrew, one tip I'd suggest for future. I'm sure you'd find similar service with with RACV as I have with RACWA - I bought a classics membership (from memory it cost about $80 more than standard/year). Aside from the usual roadside assistance services, it entitles me to an unlimited number of free tows (on flat bed truck) within 100km radius.  Really only need to use it once a year and its paid its way. Last three years I reckon i've used it at least twice a year - for me its handy as the workshop I use is about 30km from my home. Normal membership only entitles free towing only for first 10km and is limited to I think one or two a year.

[Mick A]

hopefully it is just a valve that went bad or the stem seals. Going to replace all the stem seals while I'm at it too. Also, should I drive it the 5 min trip or book a tow truck?

Valve stem seals do not affect compression. Their only job is to stop oil seeping down the valve stem into the cylinder. The valve head on it's seat is what seals the combustion chamber.

[bonno]

Hi Andrew
Agree with Mick, worn valve stem seals would not give low or zero compression. With the compression test conducted using the oil and still no compression suggests bent valve or damaged valve seat.

[Citroënbender]

The 12V motors never spit a pushrod or chew off a cam lobe? Just asking; by looking at the valve train design I'd wondered if either was known to happen.

[Al Campbell]

Would it perhaps be a slipped cam belt?

[Al Campbell]

And as a complete side issue, do you know that these cars run OK at low revs with the AFM unplugged? Until you plant your foot, then you get the mother of all misfires.