1990 LS, 5-spd, 68K, parked for two years, run for less than 200 miles since then...

Making some progress but I have noticed the engine is fairly loud on acceleration, regardless of gear or rpm. I plan to check the valve clearance this weekend.

Idle is normal and quiet. Engine sound seems normal while running at steady rpm, loud only on hard acceleration. Distributor cap and wire ends are clean w. no corrosion anywhere. Plugs are new. Some Seafoam was run through the booster line last week, made no obvious difference.

Sounds to me like an engine low on oil, but trans and engine levels were normal when replaced a couple weeks ago. Old trans oil drained looked fairly clean when drained (probably replaced at 60K)

I am thinking about temporarily replacing the stock oil pressure sw with an analog gauge, but aside from that and the valve clearance check, not sure what else I can look at.

 

If it has been sitting that long, you should take it to a mechanic to have it looked over as all of the soft lines are now suspect. The valves won't go out of adjustment if the car is just sitting there, but an oil change is DEFINITELY the first thing I would do, as well as check all other fluids and a fresh tank of gas.

 

Thanks for the suggestions. I have been going over it when I have the time.

Fuel is fresh and I ran down about 1/2 tank w some injector cleaner (Techron Concentrate) at idle and short test drives. For good measure I also pushed about 1/3 can of Seafoam through the booster hose. Engine oil, gearbox, power steering, brake fluid all drained and replaced when I started working on it. New plugs. Distributor cap/rotor clean and dry. Dry compression test normal and within 5 psi on all cylinders.

Valve clearance checked this weekend. Intake was out slightly, adjusted to .004. Exhaust was right at .007. Timing belt tension adjusted per B18A1 manual, valve cover gaskets replaced.

Running out of easy things to check, any other ideas welcome.

 

It sounds like a sensor is failing or you have a vaccum leak somewhere. Maybe a bad IACV? There's no CEL?

 

There is no CEL (almost wish there was).

The vacuum lines I can easily inspect look ok, and do not seem dried out or cracked. I can just replace them anyway. I could measure the vacuum, but not really sure what to look for.

I am not familiar with the sensors on this car.

I thought of the idle air control valve, but the idle seems fine.4, sop I have not touched it. Cold idle around 1500, then slowly drops to about 500 rpm when the engine warms up. Only a little rough, but unless you were looking for a problem, you would not notice. I have not read that section of the manual yet, but at least on my other car, the IACV is completely out of the picture once you step on the gas and the throttle opens.

Whatever it is, the noise picks up as accelerate. Almost sounds like a different engine. Not simply louder, like another kind of noise added to normal engine noise. Like an engine with oil starvation, almost, but it is not rpm dependent.

Maybe engine running lean?