should intake valves look like that?

[dysiu]

Hi, I have some problems with the engine stalling and idling rough. I thaught I found the problem by sprying a carb cleaner around intake but there is something more to it.
Yes, there was a small vacuum leak on the intake manifold gasket but after replacing it the problem persists. I can't detect the leak with carb cleaner any more. By the way... most of the vacuum stuff is removed and I'm positive I don't have any other vacuum leaks. PCV valve is new, EGR is gone, the car is carburated, 170k without major engine work.

When the intake was removed I took a look inside the head from the intake size and I noticed that the intake valves are very dirty with plenty of black oily residue on them. The manifold wasn't so clean too. Only one passage (cylinder 1) was pretty clean. Others were messy. Do you guys have any expirience with that?
Or maybe it's normal that they can be dirty... After removing valve cover everything looks nice and clean from the top.

Can it ba a problem with timing and some fumes get into the intake because valves open to early or something like that? I changed the timing belt but it was a long time ago and the car was running great for 18 months after that. The timing belt looks OK and tight. I assume it's impossible for the belt to jump a tooth or two. Distributor timing may be a little off but when adjusting with the engine on, it doesn't help no matter the position of the distributor. Distributor, coil, plugs and wires are new. I have a different carburetor but the problem persists with te other one as well. One thing I noticed that there was some water in a little tank inside the carburetor. I didn't like that. Hope it's not the problem.

Thanks for the comments.

[DanG86LX]

Looks like the idle passages (including idle jet) are somehow restricted or blocked. A simple test is to spray a lil starting fluid from the top of carb, or gas with a syringe + fine needle but without opening the throttle.
But u said u swaped the carbs.. didn't u clean (let alone rebuild) the one u put in ?

[dysiu]

There is a small possiblility that the second carb (from Ebay) had the same problem... After I put it on and observed the same engine behaviour I assumed that the problem is somewhere else.
I cleaned the second carb as good as possible with a lot of carb cleaner but I don't think I was able to clean all of those small passages.
I don't know about those idle passages... it also dies when heavily loaded with full throttle. I don't think that idle passages matter in such case...

I think I'm going to rebuild one of them. Should I just go ahead and buy a kit from Autozone or you hava a better idea? Is adjusting the carb after rebuild very complicated? Thanks.

P.S. It's killing me the fact that there was a vacuum leak on the intake gasket that i fixed and it didn't help... strange.

[zero.counter]

Here is a good link to how Qualifying Fuels can Avoid Intake Valve Deposits. Article
Here is a good diagram of what happens.


"CHEAP GAS MAKES MATTERS WORSE
To save a few pennies per gallon and to increase the competitive and/or profit margin of gasoline, some suppliers have cut back on the amount of detergent they add to their fuel or have switched to cheaper and less effective additives.

Commonly used deposit-control additives include polysibutylamine, polyisbutylene succinimide and polyisobutylene phenylamine. But these same additives also can build up on intake valve stems causing them to stick. To prevent this from happening, additional additives called "fluidizers" must also be added to the fuel. But, over time, these can contribute to the formation of combustion chamber deposits that raise compression and the engine’s octane requirements."

"The intake valves and combustion chambers should also be cleaned when you do the injectors to remove deposits that may also be contributing to driveability and emissions problems. Deposits on the backs of intake valves can act like a sponge and absorb fuel, causing a momentary hesitation when the throttle is suddenly opened. Combustion chamber deposits increase compression and the risk of engine-damaging detonation (spark knock).

Engines that burn oil typically will have heavy intake valve and combustion chamber deposits that don’t respond well to normal levels of detergent in gasoline. Additional cleaner is needed, which can be added to the fuel tank or run directly through the injectors.

To remove carbon deposits from the intake valves and combustion chambers, use a "top cleaner" type of product and follow the instructions, or use equipment that’s designed to clean the upper engine."
By Larry Carley