computrtutr

My '87 5KSQ has had a really odd problem surface recently. I will be driving, and all of a sudden, the engine RPMs are staying steady, despite the fact that I am pushing the gas pedal further. It kind of feels like I am driving into the wind. This usually happens above 1500 RPM's, at random numbers of RPM's (for example, one time it might stop at 2100, then again at 3200, then 3500, then I shift and it will do it at 1700, then 2000... you get the picture). The problem seems to stop when I push the clutch pedal, so I don't think it is an engine problem. In fact, I tried it today on the way to work... It started to do it, so I pushed in the clutch and played with the gas, and the engine accelerated smoothly both up and down, as many times as I did it, with no snags(of course, the car kept rolling w/o acceleration because the clutch was in).
I don't know what is causing this, but I am open to any suggestions. I BADLY need a new clutch (Even my throwout bearing squeaks!), which I am getting done next weekend. I am wondering if anyone knows what that problem probably is. The engine fault light is not on. Of course, I think my test that I mentioned above eliminates the engine. Anyone have any ideas?

computrtutr

(This is an 87 5000SQ with an NF engine)
I Noticed when I was inspecting lines under my hood that there is a valve which I think goes to the evap can. I don't know if this is The problem, or if it is A problem, but here is a description: The valve sits right next to this big rubber thing that's shaped like a stomach and goes from the air filter to the intake manifold. It has a vaccuum hose that goes back toward the washer fluid reservoir, then one that goes down under the passenger-side fender. When I lifted up the rubber stomach thing, there was a lot of black material on the shiny metal parts underneath. The valve itself has a hose that plugs into the front of the engine(or was it the intake manifold? I can't remember). It appears to be an original part, as it is covered in cloth and has a metal connection at the engine end. The part that connects to the valve has a small amount of dampness, which I think is fuel, because I think it has a pinprick hole in it. Is this the problem? If not, what is this hose?

QAudi42

That sounds like the idle air control valve. Not likely the problem. Could your exhaust be restricted? A plugged catalytic converter will act that way. The "bed" inside the converter breakes loose from the converter body and starts to rattle around. Eventually the bed will get small enough that it turns sideways a bit and restricts the exhaust flow. Push on the gas all you want and since it can't push any ehhaust out it just stays at the same rpm, sometimes even drops a bit. Next time it happens try to pull over while it's going on and reach under the car and hit, bang, kich the exhaust near the converter and see if it fixes it. You could get real serious and do an exhaust back pressure test. Should'nt be more than a few pounds under heavy acceleration. This is best done at a shop where they can put it on the rack, install the gauge, and check it. Another thing you could try: there's an emmisions inspection port near the upper intake plenum. It has a light blue or gray rubber cap on it. When the car acts up, pull the cap off. It'll let some exhaust escape thru the tube and you should notice a mild difference. Don't drive it that way though, you'll cook stuff under the hood. Good luck

computrtutr

The thing that makes me tend to not think it would be that is because (I don't know if you read the parent post, but...) the engine was doing its flukey thing, in response, I pushed the clutch and revved the engine... smooth as silk. When I re-engaged the clutch, the car did its flukey thing again. I am pretty sure it is in the power train, and I already know that my clutch is extremely worn... but I am not much of an authority on these kinds of problems yet.

Tom Faust

There must be something in the fuel system which measures load. I think it is handled by ionterpolation from the vaccuum plate position. It seems obvious you are getting enough gas to operate without load, but that it is unable to respond to the load. I can't see where it would be mechanical, meaning the clutch.