as it says in the headline, I am a proud owner of voyager, 2,4 liter gasoline engine from 1997.
car has manual transmission and is equipped to run on LPG (propane-butane).
so, it has two separate and independent systems of fueling the engine. even in a case that gas pump dies, I would still be able to start the car and drive it without any problems.

in a previous post, 97K... mentioned EVAP canister and what it does and that it can influence engine revs.
if it's not too much of a trouble, can you explain shortly:
-EVAP is in the engine bay?
-do I have it on my car?
-it draws vapours from tank and transfers them into intake manifold? when does that happen?

reason I'm asking:
when changing gear, engine revs stay too long as they were, and when they drop, they drop for only couple of hundred revs. it takes about 5-7 seconds to come down on idle.
went through forums, and I found that KIA owners are solving this problem with new gasket for the throttle body, which has a smaller hole for Idle Air Controler (IAC).

now.
the engine shows same problem both on gas and on LPG.
to run on LPG, car electrics must be in perfect condition. thoug, I changed IAC, O2 sensor and HT cables. sensors: intake air, MAP and TPS were checked and they work fine.
there are no air leaks on the engine, unless it's on intake manifold.
bear in mind that I open gas filler cap only once or twice a year.

would EVAP be responsible for such thing?
would new, smaller gasket fix the problem?
any other suggestion?

 

Short desc of EVAP/ Operation:
EVAP designed to prevent release of hydrocarbon (HC)emissions to the atomospehere through normal fuel evaporation. In the old days, fuel tanks were vented to atmosphere so fuel would flow through the fuel lines and not collapse the fuel tank. As the temp went up or down, the tank would vent fumes to the air, or draw in air.

Now, the tank vent is routed to a charcoal canister that absorbs the HC as the tank vents. What to do with the absorbed HC?? Well, the EVAP system waits until the engine is started and running, and then opens a small line to the cannister that allows the engine to draw in the absorbed HC. Think of a can full of charcoal with a small hole in it that allows air to be drawn through it. This is the purging process.

This system is temperature controlled (evaporation only occurs above a certain temperature) and is controlled by the PCM.

If the solenoid that controls the purge process does not shut off, or the PCM doesn't shut the purge solenoid, you end up with a constant vaccum leak. This in turn affects your idle speed, since you now have another source of air for the engine....

This is also in conjunction with the government mandated OBDII "leaktest" that the PCM does when the vehicle is started. A lot of people suffer "the gas cap code"....

Having said that, make sure all your vaccum lines are good. Visual check first, then squeeze the hoses to make sure they are still good. Then, spray lightly, some form of cleaner (carb, fuel injection, etc) onto any suspected line/s to see if that would cause the engine to race...

Also, the PCM has a hand in keeping the idle speed up.There are DFCO's, Decay Rates, and the like that may be affecting your idle speed between gears. In the past, we have solved some problems like this by "resetting" the PCM by disconnecting the PCM power and letting it sit for an hour or so to "reset". Sometimes it works, sometimes not!

Your IAC may have carbon build up as well, but I will go into that a little later on!

Likewise, maybe something has changed since the l

 

thank you for the explanation.
still have questions.

-does this mean that the solenoid is placed somewhere near/on the engine?
-and where, if you know, on my model of voyager?
-that would also mean that EVAP canister is opened for tank vetilation all the time (like when car sits through the day with tank full and fuel expanding) and that PCM is only controling when will engine inhale HC vapours from canister?

as I had problems with IAC, I had "check engine" ligt turned on, which I resetted by disconecting the battery through the night. no improvements.
all the hoses on engine have been checked, I found nothing suspicious. will check them again and even blind them just for test drive to make sure they are not causing rev problem.

-when I refill the gas, there is no suction when I open the gas cap. is that normal for this car?
-my previous car was mazda 323 and every time I was refilling, there was a strong suction of air into the tank, when I was removing the cap. mechanic asured me it was normal and in 6 years I never had any problem with engine.
-back where I live, we believe that any amount of agressive chemicals (from WD 40 or carb cleaner) can damage O2 sensor. you don't?

 

-does this mean that the solenoid is placed somewhere near/on the engine?
YES
-and where, if you know, on my model of voyager?
SHOULD BE NEAR THE EVAP CANNISTER
-that would also mean that EVAP canister is opened for tank vetilation all the time (like when car sits through the day with tank full and fuel expanding) and that PCM is only controling when will engine inhale HC vapours from canister?
YES, PCM CONTROLSWHEN ENGINE PULL VAPORS INTO IT.

as I had problems with IAC, I had "check engine" ligt turned on, which I resetted by disconecting the battery through the night. no improvements.
REMOVE AND CLEAN PINTLE WITH "CARB" CLEANER TO REMOVE ANY CARBON BUILD-UP

all the hoses on engine have been checked, I found nothing suspicious. will check them again and even blind them just for test drive to make sure they are not causing rev problem.
GOOD IDEA. SOMETIMES HOSES ARE CRACKED ON THE BOTTOM SIDE WHERE IT CAN'T BE SEEN.

-when I refill the gas, there is no suction when I open the gas cap. is that normal for this car?
IF YOU AREN'T SURE OF THE CAP, REPLACE IT. SOUNDS FINE THOUGH.

-my previous car was mazda 323 and every time I was refilling, there was a strong suction of air into the tank, when I was removing the cap. mechanic asured me it was normal and in 6 years I never had any problem with engine.

-back where I live, we believe that any amount of agressive chemicals (from WD 40 or carb cleaner) can damage O2 sensor. you don't? WE USE INJECTOR CLEANERS LIKE SEAFOAM, ETC WITH NO ILL EFFECTS ON THE O2 SENSOR. O2 SENSORS GET FOULED BY EXCESSIVE RICHNESS AND LOW TEMPERATURES, OTHERWISE THEY "BURN OFF" CONTAMINENTS AND ARE FINE. THERE ARE SOME THINGS THAT CAN FOUL THEM PERMANENTLY, BUT CHECK YOUR O2 SENSORS WEBSITE FOR DETAILS...

 

I can't find EVAP canister but there is one piece near the engine, protected by a rubber shell. a hose from intake manifold leads to it and another one from somewhere from the back of the car. also there is an lectric conector on it.
i believe that't EVAP solenoid.
only question is, why is it making clicking sound constantly when the engine is running?
it clicks like an old watch.

anyway, blinding that hose (from intake) didn't improve engine behaviour, neither did blinding the hose for EGR valve.

thanks


done that, doesn't help.
LPG instalation has a soleniod of almost the same type which also builds up carbon on it. I'm cleaning that regularly too, no changes.

checked all of them, they all seem fine.
but, cracked hose would make such a difference only if it's AFTER the throttle and IAC. right?

at least some good news
present O2 sensor is not even a year old, made some 25 000 km. I dont think it's becouse of it since I had a same problem before.
my previous O2 sensor was burned becouse of lean mixture. there was some trouble during LPG instalation and fuel-air ratio was weak, mixture was lean.
that causes high tempearture in exhaust manifold (too much oxigen) and O2 sensor can not withstand that for a longer period of time.
there was improvement when I changed it, but the high rev problem stayed.

thank you for all your effort.