in future try plugs and wires... but yea sounds like a valve job is in order.

and never clean those things with brake cleaner, its corrosive

 

Whats the ball park price for a valve job?

Flash

 

my engine guy does it for $300 for a whole head redo. new valves and what not...

 

Well, have only 100 psi in cyl 1. There's my problem.

Flash

 

Maybe not - a misfire causes the gas to wash the oil off the rings, causing low compression. Thousands of engines get rebuilt when they needn't be.

Do the smoke test to make sure it's not misfiring from a vacuum leak. AND squirt 3 or 4 squirts of oil in that cylinder, check compression again. Make sure the throttle is blocked OPEN when testing.

.

 

My engine doesn't smoke at all. Runs great too. I'm perplexed.

Flash

 

I didn't mean the engine smoked!

Attach a hose to an intake manifold port - engine OFF.
Blow cigarette smoke down the hose - if there's a vacuum leak causing the misfire you'll see the smoke coming out where it shouldn't - FIX THAT!. SIMPLE FREE!

 

That works? lol

Ill have to try that next time I suspect a vacuum leak, thanks for the tip man!

 

can also spray carb cleaner around where you suspect it to be leaking and it will suck the carb cleaner in and the rpms will rise. simple and affective.

 

Carb cleaner works too - except most carb cleaners nowadays don't burn.
Gumout works.

The other 3 problems are it's wet - liquid, often washing dirt into the hole temporarily plugging it.
And, if it's burnable, puddles form, if it ignites you have a real fire - vacuum leaks are no longer the issue!
And it removes paint from engines and fenders.

Propane works better, but it blows around and you can't see where it's going. But it can get underneath where a liquid can't. If it ignites, it flashes, scares hell out of you, but goes out.

You can get a smoke machine - $800 to $2000 - works great. But cigarette smoke works just as well. Just be careful you don't start smoking again.

We used all 3 methods in my repair shops, but the smoke machine was the best. It found things we never would have suspected.

 

So you can just unplug the brake booster hose and blow smoke into it?

Im going to try this tomorrow lol. I dont suspect a leak at the moment but this should verify im good, or show me something to fix lol

 

Brake booster line is fine.
There should be at least 1 more smaller port too.

BTW - the purpose of squirting carb cleaner or starting fluid is to get burnable "fuel" in, mixing with the air - engine speeds up. But today's computer systems quickly see the RPM change, and compensate for it. Hard to detect the change.
And, often it misses the trouble - it works if a cylinder is running lean. but the computer detects lean, and richens ALL cylinders up. Then the one the leak is affecting runs fine - but all the rest are too rich! Usually runs smooth, but mileage suffers. Useful on poor mileage complaints.


Most carb cleaners are water and soap too - like STP - mainly water.

BTW a vacuum leak is most pronounced at idle, above idle it seldom makes any difference.

If a cylinder misfires, raw gas washes the oil off the cylinder walls. The rings need that oil to seal. Compression drops - not the fault of rings or valves.
If the engine runs good at higher R's, run it there for 2 minutes, don't let it idle, shut it off.
Remove ALL PLUGS, block the throttle open, do the compression test. The first "pulse" it should reach 90% of the final reading, 2nd pulse 95% - pulse 4 pulses only - same on all cylinders.

Smoke makes finding heater control system problems easy too.

 

Ok. So, all of the sudden my rough idle is gone and the Jeep is running great again? I'm at a loss to explain it. Could a piece of carbon have broke free and caused this?

Flash