vacuum gauge reading problem

[holypaulie]

Today I hook up my vacuum gauge and reading is not steady. It's fluctuating between 20"-22" at the idle and even more during acceleration. I can't read when needle is jumping like that. What could be wrong? Any help would be appreciated.

[The Atomic Ass]

Originally Posted by holypaulie

Today I hook up my vacuum gauge and reading is not steady. It's fluctuating between 20"-22" at the idle and even more during acceleration. I can't read when needle is jumping like that. What could be wrong? Any help would be appreciated.

You've got a 4cyl engine right? It's going to do that. Use larger air line or install a small reservoir between the gauge and TB.

You might find though, that it smooths out at high-rpm.

[holypaulie]

I have tried vacuum gauge on my brother '92 corolla(4 cyl.) and reading were steady

[Andyman]

It's possible that you have a leaking valve, incorrect valve clearance or a worn camshaft lobe. Does the engine run smoothly?

One way to make the gauge steadier is to put a restriction in it. I did that by putting some wire insulation stripped from a wire into the vacuum hose. It has to fit snugly in the hose. Another possibility is to stick a threaded stud or a bolt with the head removed into the hose. It works best if there is a long length of vacuum hose between the restrictor and the gauge.

[NiHaoMike]

Put a small needle valve (available from Home Depot) in line with the gauge and start closing it until the gauge stops "fluttering". Or lubricate the gauge mechanism with a very high viscosity grease. I recommend the valve approach.

[holypaulie]

Originally Posted by Andyman

It's possible that you have a leaking valve, incorrect valve clearance or a worn camshaft lobe. Does the engine run smoothly?

One way to make the gauge steadier is to put a restriction in it. I did that by putting some wire insulation stripped from a wire into the vacuum hose. It has to fit snugly in the hose. Another possibility is to stick a threaded stud or a bolt with the head removed into the hose. It works best if there is a long length of vacuum hose between the restrictor and the gauge.

When I look at the tachometer the needle stay pretty still, but I can feel slight vibration on the steering wheel and floor mat. I'll try the trick with restriction and see what will happen.

[holypaulie]

Is it possible to have too loose or too tight(from factory) valve clearance after only 58,000 miles? I don't hear any loud valve noise, just ticking.

[The Atomic Ass]

Originally Posted by holypaulie

Is it possible to have too loose or too tight(from factory) valve clearance after only 58,000 miles? I don't hear any loud valve noise, just ticking.

I don't know how cars with adjustable valves are, but my Burgman demands clearance adjustments at nearly oil change intervals for the first 10K miles. After that it settles down and doesn't change much for 20K or more.

Cars engines have a lot more sound insulation to them, so even a very quiet noise could mean loose valves. Though really, valves that are less than half of the spec range loose, (eg, range of .006-.010 and valves are at .012), is good for low end power and fuel economy.

Tight valves don't make noise, and that's when you should worry.

[Funny]

Is the gauge glycerin filled? That would stop the majority of the needle fluctuations. Installing a needle valve would probably alter the vacuum reading, something you want as accurate as possible. Anyone here use a Wika vacuum gauge?

[holypaulie]

I connected my vacuum gauge in two different cars and it works good ad smooth. Now, I know 100%, there is something wrong with my engine not with the gauge.