Engine bogs down coming off revs

[jamesoff 10]

Hello everyone :)

 

On my 1.8 16v, I changed the oil, oil filter, and spark plugs (they were a mess) recently. The car feels better for it, but is now doing a thing where the revs sink very low when you come off the power (with the clutch in - say, when you're just coming to stop at a set of lights) before recovering to normal idle speed. It's sinking right down to about 500rpm, and particularly when the engine's warm (and, I guess, the oil is thinner) the oil light flickers very very briefly.

 

Edit: I also took the cap off the distributor and cleaned a bunch of oil out of it

 

The engine runs fine at idle and when you're driving, it's just coming off the power, particularly from anything higher than about 2500rpm or so, which causes this.

 

Anyone have any ideas of things I can look at?

 

Should I be able to hook up some diagnostic tool to this and have it tell me what it thinks is going on? If so, what would I need?

[Wild-Animal 0]

If the vacuum pipes look old then I would advise changing them, I changed all of mine recently and it curred my low idle problems. My pipes looked okay, but its the age of them they were well past it.

[seanl82 23]

Unfortunately theres no diagnostics on the 1.8 valvers, so its a process of elimination. Get someone to rev it at idle for you, and listen with the bonnet open. My guess would be vacuum pipes split/collapsing under pressure.

[jamesoff 10]

Sounds like those are the things to look at, thanks both. I'll see what I can see and no doubt be back with more questions :)

[jamesoff 10]

So I think I found a (the?) problem :)

 

 

I'd hazard a guess those two braided bits of hose (which I fished out from under the bit they're resting on now) should be joined - they certainly look like they've suffered a failure. I'll find some replacement hose and refit.

 

However, what should the other leg of the red Y-splitter attach to? It wasn't attached to anything when I found it; that end of the hose was just hanging down the side of the engine.

[jamesoff 10]

Wait, does the missing connection to to the underneath of the plastic intake manifold (hope that's the right name) just before the throttle? I've managed to attach it to there using a combination of the bits of hose I have left, but it doesn't seem to have helped the coming-down-to-idle issue.

 

While working on the intake stuff earlier (taking it off to reach some of the vacuum stuff) I found it had sucked in a load of oil at some point, so I've cleaned that out as much as I can, but it looks like the idle stabilisation valve has taken some of it in, and I'm guessing other linked parts (vacuum tubing?) may have also sucked some in. Is that likely, and will it have screwed up anything I'll need to fix?

 

(To clarify further, the T-piece lower down the line with the green near it was attached to stuff by the air box - I just removed it temporarily to have a better look at the line)

Edited September 8, 2012 by jamesoff

[jamesoff 10]

Just performing some thread necromancy to add to this that I flushed the ISV out with carb cleaner and that's significantly improved if not resolved the problem.

[Wullie 1]

http://the-corrado.net/showthread.php?52325-1-8-16v-vacuum-pipes-diagram&highlight=%2Bvacuum+%2Bhoses

 

Diagram of hoses in this thread.

[jamesoff 10]

Ah thanks Wullie, when the weather improves I shall double-check it's all hooked up right :)