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EA81 engine problem
Posted 15 October 2003 - 02:14 AM
Got a problem with my '87 4WD STD Hatchback with EA81 engine and hydraulic lifters. Engine runs great and smooth at idle with no noise at idle or startup. However, when the engine is under a load...such a revving the engine or accelerating...the car almost acts like one of the cylinders is not hitting real well. It is very hard to describe the noise it makes, but it sounds like a low pitched exhaust leak sound (almost a rumble...but not bearing rumble!) from the right side of the engine. And when it makes this sound, it is like the car is not hitting on all 4 cylinders. And it only does it when the engine is under a load. Since it has started doing this, I have noticed that the engine has lost some of its power also. I haven't read any posts addressing this problem, but it seems to be a common noise from this engine because I hear quite a few older Subes going down the road making this noise. The engine has a very slight valve train tap on the right side of the engine, but it is only noticeable with the hood up and my ear at the valve cover. And it doesn't make any valve noise on startup and any loud clacking valve noise when under a load. The engine does not lose coolant or burn any oil. I had read about the cylinder heads cracking between the valve seats, allowing the compression to seep past the exhaust valve during combustion, but have only heard about that problem on EA82s. Was this a problem with EA81s, or is there another cause for my problem? Any help is greatly appreciated.
Posted 15 October 2003 - 05:16 AM
The crack between the valves is an EA82 thing as far as I know. Never heard of that affecting an EA81.
Maybe you do have an exhaust leak - the gaskets at the heads could be the culprit. EA81's don't like exhaust leaks, and you will experience a good deal of power loss from that.
I am also thinking of the Air Suction Valve - those will vent exhaust gasses into the engine compartment when they get bad, and they make a similar noise to what your describing. And there are two of them on some engines - one at either head.
Posted 15 October 2003 - 09:55 AM
Posted 17 October 2003 - 01:43 AM
Thanks for the replies. After taking a look at it, it does appear that I have a bad Air Suction Valve. If I cover the hose when I pull it off the ASV, the noise disappears and it is quiet. Now the new question is how do I bypass this thing so I don't have to buy a new one? Any suggestions on what to use to plug the pipe that comes up from the exhaust manifold? And could a malfunctioning Air Suction Valve cause a power loss or a miss, or is that another problem? Thanks again for all your help!
1987 STD 4WD Hatchback
EA81 w/hydraulic lifters
Posted 17 October 2003 - 04:27 AM
The ASV's have been known to go into Nuclear meltdown, and cause problems with the carburator. Some of the plastic from inside of the ASV will get into the bores of the carb and cause you headaches. But I don't think it would cause missing or stumbling, could be wrong. When was the last time she was given a good tune-up? Could be the carb is dirty inside, try some fuel system cleaner, maybe a couple of tanks worth.
Where in Ohio are you? A few other members are from Ohio, and I'm only 20 miles north of the border. Plus Miles Fox is just over the border in Indiana....
Posted 17 October 2003 - 04:54 AM
Posted 18 October 2003 - 04:23 AM
1987 STD 4WD Hatchback
w/ hydraulic lifters and S/R 4WD
Posted 18 October 2003 - 06:29 PM
Posted 19 October 2003 - 10:09 PM
Posted 20 October 2003 - 02:28 AM
1987 STD 4WD Hatchback
EA81 w/hydraulic lifters and S/R 4WD
Posted 20 October 2003 - 03:23 AM
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