Another Weird Problem
 

So my '84 944 sat for a couple of years. It was parked because it had a leaky head gasket. I had a spare head, so I had it resurfaced and rebuilt it so it would be ready to go for when I decided to change the head gasket.

I swapped heads a couple of weeks ago and everything was working fine for about a week. Ever since then, it's had a really bad miss that happens sometimes under throttle, and every time I shift until it warms up. The really weird part it, when it starts to miss, it's losing compression. If it dies while it's missing, when I restart it it sounds like it's got a bad timing belt until it builds up compression and starts.

I've checked all the ignition components and they're fine. I did a compression test (cold) and I got 168, 170, 174, 175, so I don't think that's the problem. When it does it, it just randomly drops a cylinder (or sometimes two). I don't think it's fuel washing the cylinder out, because once it builds up compression again it doesn't smoke at all.

The only think that makes sense to me is if a valve or lifter is sticking. And if it is, why did it wait a week to start sticking?

Any other ideas?

Did you press the old oil out of the lifters before refitting them?

Just re-read your post, what color is the smoke?

I did not. With just about any other hydraulic lifter I've ever messed with I've always read to just set them upside down in order if you have to remove them, and that's what I did.

Not sure what you're referring to. There's no smoke or odd smells. I'm pretty well tuned in to the smell of rich or lean exhaust, and it doesn't have either one.

You said once it builds up pressure it does not smoke so I assumed that it was smoking before. My bad.

I always press the lifters to get the old oil out when doing a head refurb, it's a long slow job but it's amazing what eventually comes out.

Not sure if it's relevant but I have seen in the past where lifters can get over full and cause a loss of compression. Basically the old oil gets stuck in the lifter and causes it to stop the valve from closing.

I would suggest doing a pressure test while the problem is there that will give you an area to start looking at if compression really is being lost.

The lifters becoming over-full was the only theory that made any sense to me, but I'd never heard of that happening on a 944.

I know that on a 16v VW, if you swap cams you have to wait 30 minutes to an hour for the lifters to bleed back down, or you will have no compression due to the lifters not letting the valves fully close.

I may pull the cam tower back off this weekend and flush the lifters. What's your preferred method?

Squeeze them in a soft grip vice, multiple times.

It takes a while but you will get them bled enough to where you can compress them by hand.

Obviously it will be a bit rattly on restart until the nice new oil fills them up.

I usually pull the fuel pump relay and crank it for a bit to get some oil into them before trying to start it.

I have not seen this on a 944 but a few times on other hydraulic lifter cars.

Best of luck.

Thanks for playing everyone, but the correct answer was broken valve springs!! Fortunately, I have a spare head that I can rob the valve springs from. Unfortunately, one of the lifters was damaged from the valve that was a little sloppy.