Help - Uneven low compressions - VR6

[oxfordpaul 0]

Guys, I posted last week about misfiring esp when cold. It's getting worse and now misfires all the time but is worse the longer it's left standing. Tried new leads, cleaning ISV but to no avail. Went to a garage today who said the compressions were uneven and low but didn't record what they were (which annoyed me!!) burt also put emissions probe up exhaust and readings as follows -

CO % vol 1.67

CO2 % vol 11.33

HC ppm vol 2296 (apparently should be 50ish?)

O2 % vol 3.95

 

They have put some engine decoker in the fuel and said this may cure but otherwise it's head off and lots of dosh. Could it be head gasket - there are no signs of gunky oil or water etc and it doesn't burn oil as such? Or bores ovalised as i've read on here - how do you tell? VAG.com showed no faults - confirmed by 2 separate garages. It's done 118,000 miles and has never had any work according to a very complete history. Am I harming it further by running with a bad misfire - they said to run it for 2-300 miles to let the cleaner work - please help!! :(

[dazzyvr6 0]

well you wont be doing the cat much good,if its got a missfire then it must be electrical related,is it a dizzy or coil pack vr6?

[oxfordpaul 0]

it's a coil pack one - but this surely doesn't account for low and uneven compression? And i've been told coil packs either work or they don't - is this true?

[dazzyvr6 0]

nope,if its got a hairline crack it will missfire.especially in wet weather

[Supercharged 2]

Take it to Stealth...

[oxfordpaul 0]

Is that right...mmmm could be the coil pack then but i'm still stuck with poor compression so does it need a head gasket as well? I prob will take to Stealth - bought leads from them last week and they seemed great - will call them tomorrow. Can someone confirm though about compression - would poor spark from faulty coil pack cause low compression?

[dazzyvr6 0]

you say it doesnt burn oil,what state are your plugs in,pay particular attention to numbers 1 and 6 as they seem to be the most likely to go first

[Kevin Bacon 5]

A poor spark won't affect the compression but it will make the engine run badly.

 

Spray a fine mist of water onto the coilpack at night and look for arcing. If none, the pack is alright. Spray some water around the plug leads too (preferably when engine is cold) to check those too.

[oxfordpaul 0]

Well I've just tried squirting the coil pack and there's no sparks. I can see a bit of sparking from the 1st cylinder on the left front but the leads are new so why would this be? Perhaps not pushed on far enough?

 

Does any of this explain why it's over-fuelling and running so rich though?

[dazzyvr6 0]

dodgy lamda probe?

[oxfordpaul 0]

Would this account for high emissions AND rough running/misfiring?

[Kevin Bacon 5]

There should be no sparks at all from the leads or pack. Try pushing cyl # 1 lead on a bit more, with the plastic tool if you've got it. Or better still, invest in a metal hazet tool from VW.

 

Yep, HT arcing would definitely cause high emissions and rough running as the fuel is not being burnt fully.

[emax 0]

Hi oxfordpaul,

 

I also had similar running symptoms to you and had a compression test done on my car.

 

All cylinders were high except #2 but I'm in doubt as to whether they performed this test on the engine while warm (very important apparently). I have the Schrick manifold which needs to be removed to gain access to three of the spark plugs.

 

I got the injectors refurbished andthat solved my starting problems although I still intend on carrying out my own compression/leak down tests when I get around to refitting my standard manifold.

 

Maybe a second opinion wouldn't be a bad idea? Could it be the head gasket?? Any signs of cross-contamination between the oil/water?

 

Good luck!

[oxfordpaul 0]

Thanks emax, spoke to Stealth today and booked it in but they can't do it till 22nd Nov! No sign of head gasket gone but did see sparks from plug lead in the dark (the front left one). The leads are new but there was a lot of oil round this plug which they said may be the problem - would be caused by leaking rocker cover gasket. I'm going to buy the Hazet tool as Kevhaywire suggested and make sure leads are firmly connected after cleaning plug holes etc. It starts and idles perfectly so no issues there - i'll keep posting progress - any other ideas welcome...

[Rpmayne 0]

Some tuneup garages can check your compression by measuring the starter motor current as it compresses each cylinder. The lower the amount of current needed to move the cylinder the lower the compression as I understand it. Might be worth a try to back up the other test.

 

When I took the plugs out of mine, 1 & 6 were soaked with oil. And was using about 1litre/1000mls, greyish smoke when nailing it etc. If you're not using any oil I would have thought its abit weird if the bores/rings are the problem.

 

Does your coolant overheat or the cap keep blowing? Misses had a polo which kept doing that, turned out to be a leaking head gasket which was compressing the coolant system. Local garage found that by putting a bung with some kind of liquid it it which change colour if any gases were present.

[oxfordpaul 0]

Checked rocker gasket - no obvious big leaks, will check plugs on 1 and 6 later although it was serviced by specialist 1800 miles ago and no reports then of fouled plugs. No probs with coolant or any pressure out of filler cap or dipstick which apparently is a sign. I'm really beginning to think it's the coil pack and may just invest in one to check it out - unless anyone has a spare one I could just try?