I Found My Rough Idle Issue (Low Compression)

[Moreflying]

Well I thought I'd share my news. After a lot of poking around I got to the compression check and it's not good. #1 58 psi #2 100 psi #3 150 psi #4 150 psi. I'm off to do a leak down test. I hope it's a valve and not rings. Wet test didn't increase it but by a few psi. My guess is an intake valve. Spark plugs are dry and look fine. Okay. If anyone can give any advice on what to look out for when pulling the head such as pitfalls, procedures, items to replace and so on please let me know. I guess my timing belt job just turned into more this summer. I'm not going to complain too much here. At this point it has almost 220,000 on it. Thanks for any advice.

 

[Rogue_Wulff]

With #1 and #2 both being much lower than the other 2, it could also be head gasket related.
With 220K on it, I'd say pull the engine and give a full freshening up if the valves are causing the issue. Who knows, you might be able to get another 200K+ out of it that way......

 

[kimcrwbr1]

Have you tried the seafoam trick. pull about 1/3 a can in the brake booster vacuum line after the engine is wamed up and quickly shut it down you will need to feather the throttle so it dont die. then wait about 30 minutes to an hour letting it soak in good then start it and run it about 2500 to 3000 rpm until the smoke clears. and then see if your compression numbers come up. It could be just carbon build up you can add the remainder in the fuel tank when you top it off to flush the fuel system also. Worth a try before tearing into it anyway.

 

[Moreflying]

*I might give the seafoam a try.

*My leak down test was interesting. Cylinders 3 and 4 showed no signs of leaking through intake or exhaust and no bubbles in the radiator. What was weird was the gauge showing an average of 65% loss through the bottom end. I heard the hiss through the dip stick. I don't get that when I've got 150psi. compression on both of these cylinders.

*Cylinders 1 and 2 both have leakage through the exhaust valves (more so on #1) and I heard some leakage through the dip stick on both as well. #1 was loosing 75% and #2 at about 70%.

*I'm not sure how 2 cylinders with good compression show almost the same loss as 2 cylinders with leaking exhaust valves and lower compression..one substantially more. Maybe I need to rethink something.

Then only thing I can say for sure is #1 and #2 exhaust valves are leaking.

*I have a hard time believing the loss percentage numbers (possibly the gauge). With those readings I would think my plugs would be wet with oil, smoking out the tail pipe, no power, possible coolant in the oil.. and I have no signs of any of this. I might test this gauge on my new car and see what it does. I'm not sure if I've missed something here. I'd like to think I can pull the head and have a valve job done.

BTW..I just passed my smog check with flying colors too.

Side note..cranking the engine by hand for the test makes for a wicked top end tick after starting it back up. I took several minutes for it to clear up. What is that all about? It did that when I changed my timing belt a while back too.

 

[kimcrwbr1]

The leaky valves will definately cause compression loss. How good is your oil pressure, If you have decent oil pressure and the seafoam gets it running better I would run it till it pukes. In the mean time you can work on rebuilding another engine plug and play or search for one already rebuilt for cheap or a low mile bone yard motor with good numbers. I personally have always gone with bone yard parts (engine, tranny, rear axle) with good success. For the engine I look for engine fires, you know the engine was shut down fast and you should replace all the gaskets and seals anyway while you have it out.

 

[Moreflying]

I've got good oil pressure according to my gauge. I will verify that with a mechanical though from the sending unit. I'm going to try the seafoam I.V. drip into the vac off the booster. Then go to 30 w oil and hyperlube. I think I may do a valve job to get rid of the imbalance for now. What is the concensus on that?

 

[kimcrwbr1]

Do the seafoam first and if it dont leak oil just use a good synthetic and a new filter. You dont need to add anything to thicken it up you can add 1/2 a quart of ATF and run it for 100 miles then do a normal oil change with 10W30 synthetic and a motorcraft filter if you thicken it up it may not make it to the upper end properly. I am guessing that is the case the oil in the pan is not getting up there very fast it could be a clogged filter. Change the filter and add 1/2 a quart of ATF drain a little off if it is full then run it at medium speeds for a bit then drain it good add new oil and filter. It just sounds like it has been neglected and put a new PCV valve in it at the same time and clean/change the breather filter.

 

[Moreflying]

I'll give the seafoam a try and see if it breaks any carbon loose. Not so sure I want to put ATF in with the oil. I'm thinking of putting seafoam in the oil. As far as negligence...no. I'm the original owner and it has been taken of. You don't make it to 220K letting it go.

Ill pull the head this summer and see what's up.

 

[Rogue_Wulff]

ATF in the oil is a SAFE thing to do. I've used it many times to help clean out an engine that was gunked up inside. Unlike seafoam and other "flush" type products, ATF will not dissolve all the gunk at once making a plugged oil filter or oil pump pickup a concern.
4 qts oil, 1 qt ATF, and a new filter. Change it after 500-1000 miles, whenever the oil starts getting really black. Repeat until the oil remains clean for up to the normal oil change interval.

It really sounds like your main issue is just a couple exhaust valves that aren't sealing well. A valve job would likely return the engine to good condition, but with that many miles on the lower end, it could cause the rings to start leaking rather soon. That's why I suggested pulling the engine and giving the lower end a freshening up. You might be able to get away with just new rod/main bearings and rings with a good hone, depending on the bore/crank wear.