So, I've been chasing a rough idle issue since I bought the truck back in September. I'm fairly certain that I'm never going to resolve it, but yet I persevere.

Tonight, I finally got around to using the compression tester I picked up in December. My numbers are thusly:

8 151 7 155
6 151 5 159
4 148 3 165
2 149 1 165

How does that look? Does it seem odd that the left bank is a bit higher than the right, or is that nothing to worry about?

Being as this is the first time I've done a compression test, I'm not entirely sure how to interpret the results.

Any ideas?

 

Generally, as long as they are all within 10% of the highest, you're good. Yours look OK.

 

those are pretty good numbers for a 10 year old truck that's probably got 100-150k on it. they're reasonably equal, and none of them suck. (like zero or 50 or 75). so your problems are not rings, valves, heads, or head gaskets.

consider cleaning injectors, and maybe the rail too. tune up, etc.

 

An old mechanic once told me that you should write down the reading after three (or so, as long as all have same # of rev's) spins of the crank for all cyl's and then indicate which cyl's require more rev's to reach max comp. Something about the cyl's that req more rev most probably have worn rings and those that max out at a lower reading point more to a gasket or valve. I've also read this in a engine building manual, I'll see if I can find it.

 

That is right where mine is at. My truck runs fine. I will be doing another test this weekend before I change the oil to test the effectiveness of Restore.