Low vacuum - Inlet cam skipped a tooth?

[myne]

For about the last week, my gze has been struggling to idle correctly. It's actually averaging a mere 10-12"hg at idle, which is down from the usual 20"hg.
If I give it a tiny bit of throttle, by 2000rpm, the vacuum is up to 20 and the engine is smooth.

The only thing I can think of that could cause this is the inlet cam skipping a tooth or a large air leak between the AFM and the ports. Boost seems more or less the same as always so I'd ruled out an air leak.

[Ben Wilson]

Pulling the front cover and checking the cam timing shouldn't be too hard. 10-12" is bloody low, but if you're seening 20" at other revs I suppose it's possible.

[takai]

My GZE for a while was giving me 10-12"hg, and the problem ended up being that there was a small split on the underside of one of my IC hoses, just shaped right so that there wasnt a significant boost leak, but that there was a vac leak.

Strangely enough the HKS pulley managed to provide enough boost to make this a full blown boost leak.

EDIT: Oh yeah, meant to say, that dont touch the CAS now. While the ECU is in "low vac" mode it will hunt for idle, and so when you try and lock the timing it wont actually lock. Plays havoc with trying to reset the timing... trust me.

[SL666]

my 1j only pulls about 12 or so when cold, but around 15 at normal warm idle..

decrease in performance?

generally speaking, if one of your cams has skipped a tooth there be problems.. pinging, drastic change in power delivery etc..

i'd do a compression test... any more blowby (or oil in the blowby) that usual?

[EldarO]

youve got a hole in one of your vac lines, or IC lines.

mine idled like a whore until i replaced a vac line that had split up the arse.

Eldar.O.

[myne]

intercooler has a hole!

Dodged it with some plasticine, a bit of manifold and a cv-boot retainer.
Scarily it seems to have worked perfectly.
I hated that intercooler from day 1 so I suppose it's to be expected.

[faulksy]

intercooler has a hole!

Dodged it with some plasticine, a bit of manifold and a cv-boot retainer.
Scarily it seems to have worked perfectly.
I hated that intercooler from day 1 so I suppose it's to be expected.

plasticine...myne new be all and end all. turbo manifold prototypes, i/c repairs

becoming the true bush mechanic

[myne]

It was there. I would have preferred something with tar - like roof sealant, but you gotta go with what's avaliable.

[myne]

Oh, and asif I havent been a bush mechanic from day 1!

Remember how I drove 10km through the hills with a blown uni joint?
That was class!
I used a few bits of wire, a u-bolt, a fan belt and some rags to make that work.
Clunky but effective.

[stradlater]

That's true Macgiva style.... Did you use any paddle pop sticks?

[EldarO]

matches, some string and a straw FTW!

I suggest you scrape that stuff you used off at the first possible chance, and replace it with some Quiksteel, or the like.

Eldar.O.