Wilsontom841

So I have a 97 ex I picked up cheap with a slight miss at low rpms and number 3 cylinder acts dead (unplug the spark plug wire and injector with just a very slight difference in idle) tested wires and plugs witch are good and tested injectors witch are all good. Done a compression test and got 175 psi on this cylinder. It is a high mileage motor. Just adjusted the valves and helped alittle but still have a ticking aound and a slight miss at low idle. I have everything to put a new head on just not the head yet so I wanna know if a bent valve will cause this. Thanks!

Wankenstein

May or may not be bent..just poor seal (valve leak),OR: worn valve springs, worn valve guides or breached headgasket that is causing compression loss. Any metalic noise in the cylinder head? Did you do a dry and wet compression test? What are the compression numbers for the other three cylinders? If you want to isolate leaking valve(s) then do a leakdown test on it.

At this point it seems that a valve (job) lapping might be in order to seal the valve(s) leak. However, as I mentioned a leakdown test will provide further info. Here's another (less effective) method that may help diagnose: http://www.gregsengine.com/using-a-vacuum-gauge.html and video:


Harbor Freight Vacuum Gauge: http://www.harborfreight.com/fuel-pu...ter-62637.html

Wilsontom841

How would I do a leak down test?

Wankenstein

Googs will tell you: https://www.google.com/search?num=50....0.wN7ae2oqLF8

If you don't have a decent compressor than you're better off bringing it to a trusted mechanic to do it. The price of a good compressor, leakdown gauge, and hose will be at leat twice the price of a mechanic's one time fee. Also, it takes time and experience to do a leakdown test properly as it can be difficult to keep the cylinders from moving off of TDC when 100+ psi of air is being pushed on them.

I had one done by a mechanic a few months ago and on one of the cylinder he couldn't prevent it from moving off of TDC. He (not-so-willingly) held the crank in place (piston at TDC) with a breaker bar and socket on the crankbolt. This (young) guy has some serious grip strength to keep the cylinder place while he injected air into it. He let me try holding it and I had to give it all I had to keep it from moving and I still didn't get it to a point were it completely sealed of the valve. He did though and I was impressed because he's skinny and lanky but, obviously damn strong. Probably would make a good arm wrestler or american ninja warrior if he tried it.

ezone

One figure by itself has little value. Need all of them to make a comparison.

What's the compression test results for each of the 4 cylinders?