New user. First time RV owner. Purchased 1989 Dolphin Toyota RV V-6 76,000 miles in "excellent condition" for 9k in Aug. 2016 from a less than honest seller. Put additional 3k into repairs from roof leaks w/ related damage, gas tank filler hoses, rear axle air bags, belts, hoses, brakes, wheel bearings, wheel cylinders, radio, plumbing, heater, on and on. Switched to semisynthetic engine oil, full synthetic in the rear differential. Rear differential ran much cooler after switch. Engine oil has been clean through several changes, and uses less than a quart between changes if driven hard. Problem: ran rough after last 3,000 mile road trip, switched plugs, rotor, and cap. Ran compression check and range was 130-150# except #4 at 90#. Engine runs smooth, but I hear a slight miss through the exhaust possibly from exhaust valve leak? I plan to run the test again this weekend. I am borrowing a leak down tester to do a more thorough check on that cylinder. It is a new problem and doesn't seem to have changed the power available, although it is already extremely underpowered for mountain terrain. I can access that bank easily to check and change the shims on that side of the engine. Are the shims something that can be easily found? One local dealer's service writer would not let me talk to the head mechanic to see if anyone on staff was even familiar with valve work on this engine, and he was quick to dismiss me as an annoyance to his day. Another dealer at least spoke to me at length in the service department about the possibilities and costs. $95. per hour is too costly for exploratory diagnosis which, with a valve job, timing belt, and pump put the cost over the range of a newly rebuilt engine with 3year 100k warranty. I have a Chilton's manual that covers all the work required, but it beyond my skillset to take on more than a valve check and shim on the one bank. Any advice up to and including certified shops in my area (southern Illinois) that are qualified and recommended for this kind of work would be appreciated. There is no rust, all other systems are good, and it is too nice to send to the crusher.
