sid_vicious Posted December 5, 2011 Share Posted December 5, 2011 Hi, I've got a 2000 Outback that I bought with a seized engine. I replaced it with another engine that had about 90,000 miles on it. It runs, but idles rough and bogs down a bit on acceleration. I only recently got a CEL for misfires in cylinders 1 and 3, after driving it for a few months. It has new plugs and wires, ignition coil, valve cover gaskets and spark plug tube seals. I replaced the timing belt, but checked timing multiple times to be sure it's not off. I even tried timing it intentionally a tooth off from the marks on the cylinder 1/3 side to be sure there wasn't some weird reason that would fix it. I've also checked all vacuum connections and found no leaks. I don't have a compression tester, but I did just hook up a vacuum gauge and found an interesting reading. At idle, I get a solid 20 inHg. No fluctuation at all. If I manually increase the engine speed it begins to fluctuate between 15-25 constantly. I don't have any overheating, coolant loss or bubbles in the coolant tank to suggest a blown head gasket, but does the fluctuating needle indicate a potential valve problem? I read as much as I could about interpreting vacuum readings, but I couldn't seem to find anything about my situation, where the reading is steady at idle but then fluctuates widely with increased RPM. Thanks a lot. Quote Link to comment Share on other sites More sharing options...
naru Posted December 5, 2011 Share Posted December 5, 2011 Vacuum readings can be tricky to diagnose. Yours sounds like classic weak valve springs. I would disconnect injectors one at a time to isolate the problem. I`m thinking a bad head gasket could be similar. Quote Link to comment Share on other sites More sharing options...
jarl Posted December 5, 2011 Share Posted December 5, 2011 - "Weak or broken valve spring" - "Defective ignition system or throttle chamber idle adjustment" (image from jdmfsm) Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted December 5, 2011 Share Posted December 5, 2011 Run a compression test just to see..... Could be burned exhaust valves - did you do a valve adjustment when you repalaced the VC gaskets? I had a similar and very frustrating problem on a 25D not long ago. Turned out the owner did the HG's and timing belt himself and didn't properly torque the intake cam pulley bolt. It had chewed up the front of the cam shaft and allowed the intake cam to advance the intake valve timing about 15 to 20 degree's. This caused the compression reading to go UP on that side of the engine (about 220 compared to 185 on the 2/4) and resulted in 1/3 misfire codes, etc - just as in your case. It certainly sounds valve train related since that's the only thing the 1/3 cylinder's share is a common camshaft. GD Quote Link to comment Share on other sites More sharing options...
sid_vicious Posted December 6, 2011 Author Share Posted December 6, 2011 I did not adjust any valves when I replaced the valve cover gaskets. I suppose I should have checked them before I put the engine in. At least the 1/3 cylinder side is easy to get at, so I can have a look at the clearances in the next few days. I'll round up a compression gauge, since I should have one anyway, and see what I come up with there as well. Quote Link to comment Share on other sites More sharing options...
sid_vicious Posted December 6, 2011 Author Share Posted December 6, 2011 I just finished testing compression. I had the engine at operating temperature when I did the test. The first compression stroke was about 100psi on all four cylinders. A few more strokes brought pressure up to about 195-200 on all cylinders. Is it normal for that first stroke to be low? It acted the same on all four cylinders, so it didn't seem like a problem to me. Quote Link to comment Share on other sites More sharing options...
sid_vicious Posted December 10, 2011 Author Share Posted December 10, 2011 After doing a compression test, I guess my idle and misfire problem is not from valve/piston ring/head gasket problems. I went back to look at all vacuum hose connections and again found no problems. Here's something I found to be strange: I removed the vacuum hose leading from the intake manifold to the purge solenoid valve and the engine smoothed out. Of course, there was hissing from the manifold port and the idle went high, but the engine seemed to run a lot better. I drove it around the block a couple times with the hose unplugged and it drives much better. Is there some way the engine's not getting enough air and this opening is letting enough in to make the engine run better? The air filter is new, and the idle air control valve is also pretty new. Quote Link to comment Share on other sites More sharing options...
kalia1000 Posted December 11, 2011 Share Posted December 11, 2011 I had a similar and very frustrating problem on a 25D not long ago. Turned out the owner did the HG's and timing belt himself and didn't properly torque the intake cam pulley bolt. It had chewed up the front of the cam shaft and allowed the intake cam to advance the intake valve timing about 15 to 20 degree's. This caused the compression reading to go UP on that side of the engine (about 220 compared to 185 on the 2/4) and resulted in 1/3 misfire codes, etc - just as in your case. Quote Link to comment Share on other sites More sharing options...
nipper Posted December 11, 2011 Share Posted December 11, 2011 Vacuum readings can be tricky to diagnose.Yours sounds like classic weak valve springs. I would disconnect injectors one at a time to isolate the problem. I`m thinking a bad head gasket could be similar. Actually they are really simple to read, don't know where they can be dificult comes from http://www.classictruckshop.com/clubs/earlyburbs/projects/vac/uum.htm Quote Link to comment Share on other sites More sharing options...
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