low compression

[jason bond v6]

hi i own a uk model v6 4.0 sohc 98 explorer with a gas conversion ive changed the plugs for iridium power plugs, new leads, new mass air flow meter, new cam chains, new gear box, new idle control valve,
i have changed most of these things cus she has lost loads of power.
i did a compression test on number 5 and 6, 5 was ok and 6 had half the compression OF 5. also number 6 plug was oily wet black,
i took the air filter out and noticed that it was oily in the pipe, there are 2 thin pipes that go into the big air filter hose 1 was dry and the other was oily wet, this pipe runs to under the idle control valve, i took the idle control valve off and it has 2 pipes than come in through the bottom of it. one was dry and 1 was wet with oil the 1 that was wet also splits off an goes to the back of the engine. i took the oil filler cap off and looked inside it looks clean and normal.
she stalls every time i stop but runs ok once she has warmed up but still with the loss of power. she doesn't overheat or use loads of oil, she doesn't leak any oil on my drive. any ideas on what to look at next. thanks for any help

 

[Cobraguy]

Do a leak down test on it. Check every cylinder. You only checked two...you might have 4 more bad ones. Regardless, you need to find out just how big a problem you have. This sounds like ring problems. (Blow by)

 

[jason bond v6]

Do a leak down test on it. Check every cylinder. You only checked two...you might have 4 more bad ones. Regardless, you need to find out just how big a problem you have. This sounds like ring problems. (Blow by)

cheers for the reply m8 il check every cylinder and let you know. this may sound stupid but what is a leak down test.

 

[jason bond v6]

cheers for the reply m8 il check every cylinder and let you know. this may sound stupid but what is a leak down test.[/QUOTE


can anyone help me with this please

 

[marragtop]

A leakdown or cylinder leakage test is similar to a compression test in that it tells you how well your engine's cylinders are sealing. But instead of measuring pressure, it measures pressure loss.

A leak down test requires the removal of all the spark plugs. The crankshaft is then turned so that each piston is at top dead center (both valves closed) when each cylinder is tested. Most people start with cylinder number one and follow the engine's firing order.

A threaded coupling attached to a leakage gauge is screwed into a spark plug hole. Compressed air (80 to 90 psi) is then fed into the cylinder.

An engine is great condition should generally show only 5 to 10% leakage. An engine that's still in pretty good condition may show up to 20% leakage. But more than 30% leakage indicates trouble.

 

[robertoa1a]

The above is great advice and regardless it looks like you have a lot of work in the near future. The leak down test Is great because It can give you an idea about how much life is left in the engine. In the states parts availability, new and used is plentifull. Most of us make decisions on this. I would starting looking for a crashed (engine doner) vehicle but in the UK maybe it's better to rebuild the engine. You can try Sea foam addative as a last effort to try to get a little more life out of that engine and you might get lucky.

 

[Cobraguy]

Here is an excellent gauge for the price:

http://store.summitracing.com/partdetail.asp?part=SUM-900010

It's a tool to keep in your tool box as you will use it for years. Here is a Car Craft article that helps explain what to do. They tend to ignore the head gasket leak as they feel that would be obvious. Don't assume that.

http://www.carcraft.com/techarticles/116_0406_cylinder_leakdown_tester/index.html

The one thing I would suggest you do is leave all the plugs in the engine except the one you are working on. It will be a lot more difficult to turn the motor over, but that's the reason why you do it. If you aren't dead on TDC, the compressed air will tend to shove the piston down the hole. Leaving the plugs in really helps prevent that. But if you have your balancer marked dead on at 90 degree intervals, you won't have that problem anyway.

 

[jason bond v6]

Here is an excellent gauge for the price:

http://store.summitracing.com/partdetail.asp?part=SUM-900010

It's a tool to keep in your tool box as you will use it for years. Here is a Car Craft article that helps explain what to do. They tend to ignore the head gasket leak as they feel that would be obvious. Don't assume that.

http://www.carcraft.com/techarticles/116_0406_cylinder_leakdown_tester/index.html

The one thing I would suggest you do is leave all the plugs in the engine except the one you are working on. It will be a lot more difficult to turn the motor over, but that's the reason why you do it. If you aren't dead on TDC, the compressed air will tend to shove the piston down the hole. Leaving the plugs in really helps prevent that. But if you have your balancer marked dead on at 90 degree intervals, you won't have that problem anyway.

its bad then m8.

 

[jason bond v6]

also i hear a popping sound when i put ma foot down just 1 pop and only when im going slow and then give it sum gas

 

[robertoa1a]

The popping is provably unburned fuel intering a hot exhaust and exploding there. You are provably suffering a severe loss in the metric equivelent of horsepower. How long has this been going on?

A lot of us are still stuck using the english system of measuring here (irony).

 

[jason bond v6]

i got the jeep about 2 years ago, it lossed the power within the first month of me owning it, the first thing i did was change the plugs and leads, i ran the engine for about 5 mins then turned it off check all the leads were on ok then tried to restart it but it wouldnt start, i took the new plugs and leads off and put the old 1 back in but still it wouldnt start, i put all the new 1 back in and the new leads back on went to bed and it started first time in the next day, wierd i know spent 12 hrs trying to start it.
had it in to my local garage and he said the idle controle valve needed changing, did that still ran the same, then the cam chain runners things broke so had them changed still ran the same, then the garage said the mass air flow meter might be to blame so had a new 1 of them still ran the same, so then i lossed all trust in the garage, by this time i have owned the car nearly a year, i then changed the plugs for irrium plugs and high power leads and someone surgested it might be the cats so i had my emmisions tested and that came back ok, then the gearbox broke, about 9 months ago and i only just managed to get it fixed last month.so she has been sat for 8 months on my drive. so in the 2 years she has cost me loads and the wife is goin to cut ma balls off if i spend any more on her, so i have talked the wife into letting me keep her if i can fix her myself, i dont know much about cars but if i take something apart i can put it back together, i run my own property maintenance company so im good with my hands and i have some good mates who will help me too.
1 mate of mine said that the oil breather pipe is near number 6 plug and it is a small pipe that gets blocked up in the rocker cover and causes it to give low compression in number 6, he dont know but thinks it might be worth a look? cheers for the reply m8

 

[Cobraguy]

Or it's coughing back through the intake. That would be a bad thing. Not good on MAF sensors...and it can actually break a plastic intake manifold.

 

[jason bond v6]

from inside the car it sounds like metal flexing from outside it sound more like a pop?