85 240 Strange Knocking Issue

[bobman360]

Hey! First post here, I promise I've read a lot of stuff and searched around and can't seem to find a situation very similar. Car is an auto wagon with 205k. Recently it has started knocking really loud (afraid it is rodknock or similar mechanical problem) but only when in gear. It seems to have trouble staying running as well. I replaced the knock sensor as it was damaged but this has had no effect. Pulled the plugs and #4 has some white deposits. I also did a compression test which has to be the most confusing part yet.
Cyl 1. 160
Cyl 2. 180
Cyl 3. 112
Cyl 4. 110
I unplugged the maf while the car was running and it worsened the issue so I believe that eliminates the maf as a possible suspect? (Sorry if it's not called a maf, you know what I mean)
The car had some knocking and overheating issues last summer but I replaced the radiator and the cracked intake manifold gasket at that time and it seemed to solve the problem.

[hiperfauto]

With those compression readings I'd assume the head gasket is blown between 3 & 4. Do a leak down test with all the spark plugs out and listen for air coming out of the neighboring cylinder.

[bobman360]

well it's definitely blown there like you said, just did the leakdown test. I hope that's the only problem and I don't have rodknock as well

[hiperfauto]

You probably don't have anything to worry about. It's common for a head gasket that's blown between cylinders to make a knocking noise. Just make sure to have the head surfaced since it's probably worn where the gasket blew.

[84B23F]

Originally Posted by bobman360

started knocking really loud

Take lid off of Coolant Tank, place palm over hole with a cold engine running...with other hand, increase engine RPM...any pressure?

[Otto Mattik]

Originally Posted by bobman360

Hey! First post here, I promise I've read a lot of stuff and searched around and can't seem to find a situation very similar. Car is an auto wagon with 205k. Recently it has started knocking really loud (afraid it is rodknock or similar mechanical problem) but only when in gear. It seems to have trouble staying running as well. I replaced the knock sensor as it was damaged but this has had no effect. Pulled the plugs and #4 has some white deposits. I also did a compression test which has to be the most confusing part yet.
Cyl 1. 160
Cyl 2. 180
Cyl 3. 112
Cyl 4. 110
I unplugged the maf while the car was running and it worsened the issue so I believe that eliminates the maf as a possible suspect? (Sorry if it's not called a maf, you know what I mean)
The car had some knocking and overheating issues last summer but I replaced the radiator and the cracked intake manifold gasket at that time and it seemed to solve the problem.

Always turn off the ignition prior to connecting/disconnecting a component such as MAF/AMM.

[240Redblock]

Had HG blown between cyl. 2 and 3, sounded like pinging from timing advanced too much, replaced HG (head was within 0.002) and sounded much better (except when I accidentally had timing at 25deg+, almost ran backward from backfire!). Did not have oil in coolant or overheating issues, noticed precipitate in the oil, that and sound were my only clues.

[Otto Mattik]

Originally Posted by 240Redblock

Had HG blown between cyl. 2 and 3, sounded like pinging from timing advanced too much, replaced HG (head was within 0.002) and sounded much better (except when I accidentally had timing at 25deg+, almost ran backward from backfire!). Did not have oil in coolant or overheating issues, noticed precipitate in the oil, that and sound were my only clues.

sayin you gonna start a new thread ?