Need some help diagnosing...

[syfir]

I have a 93 Festiva. It is running rough especially at idle. When I first start up the car, it runs fine for about 20 sec, then it starts to shudder periodically. When decelerating, the car will almost cut out. This effect is also present at higher engine speeds, but is much less noticeable. I have checked the coil, plugs have less the 2k on them, new wires as well. I checked and cleaned the PCV valve, tightened the throttle cable(was a little slack there), checked vacuum hoses, checked voltage at TPS. I went to check what I thought was the EGR valve but it was full of coolant. If anyone knows what this part is I would also be curious to know. It is a cylindrical part mounted to the head on the rear driver side. It has one hose going to the air intake, one hose to the intake manifold, one hose to the head, and it looks it is directly connected to the head(not a hose, just bolted in). I pulled off the top hose of what I thought was the vacuum motor and sucked up a bunch of coolant with a vacuum pump. Any ideas or help is appreciated. Thanks.

[syfir]

Would also like to check the ignition control module, but have not been able to find it. Does anyone know its location?

[GenevaDirt]

welcome to the board....sorry to say I am unsure of the problem...but it does not sound normal. I am sure that someone will respond soon. In the meantime...take a sec and add your location to your profile....someone may be close to lend a hand or something.

[jglutz]

Change the rotor and cap or atleast clean the internal up. Very common symptoms of water inside the dist cap or excessive corrosion on the post....just use some light sand paper or stell wool.

Also check all of the air inlets ducting for loose joints or cracks. This will mess witht he AVF and create havoc. Also check all of the vac lines.

The device that leaked coolant...if it is under the intake manifold near cylinder no.4...it is the ISC. 2 of the oses contain coolant. Your discovery is expected.

Just a start with two common problems.

[mattswabb]

2nd on the cap and rotor. Very commom problem on the festiva.

[syfir]

Thanks, will change out cap and rotor tonight. I checked the vac lines pretty good, but I will go over them again with the carb cleaner just to make sure. Also, yes that was the location of the ISC. What part is that? Is the intake liquid cooled?

[CharlieZ]

Why would the ISC have coolant in it?

[ejp2fast]

If anyone knows what this part is I would also be curious to know. It is a cylindrical part mounted to the head on the rear driver side. It has one hose going to the air intake, one hose to the intake manifold, one hose to the head, and it looks it is directly connected to the head(not a hose, just bolted in). I pulled off the top hose of what I thought was the vacuum motor and sucked up a bunch of coolant with a vacuum pump. Any ideas or help is appreciated. Thanks.

that is your fuel pressure regulator i am pretty sure. can someone second that?

[CharlieZ]

My guess is that your looking at the ISC-BPA or Idle Speed Control- Bypass Air valve. It has a wax pellet inside that expands and contracts with engine temperature. When the engine is cold, the valve allows more air to enter the plenum (manifold), by bypassing air around the throttle body, raising the idle speed. As the engine warms up, less air is bypassed into the plenum, lowering the idle speed to curb idle. If you disconnected the hose that goes into the plenum, it would vacuum anything nearby into the engine. If the engine was cold at time of disconnect, either hose will have a vacuum at the loose end.
Hope this helps

[jglutz]

ISC function....not perfect but something like this......
the ECU sends a signal to the ISC to increase air flow to the engine at idle. As air flow increases the VAF provides feed back to the ECu thus the ECU also increases fuel flow. The signal to the ISC is proportional or PWM (pulse width modulated).

Anyway, the hot water works internally on the other side of the ISC valve with a wax motor. If the water is hot, the wax heats up...expands...and closes the valve.

Analogous to the choke on a aspirated engine.

Maybe not perfect....but I think I'm pretty close.

[CharlieZ]

ISC function....not perfect but something like this......
the ECU sends a signal to the ISC to increase air flow to the engine at idle. As air flow increases the VAF provides feed back to the ECu thus the ECU also increases fuel flow. The signal to the ISC is proportional or PWM (pulse width modulated).

Thanks for the info. I knew there were two type of ISCs one wax the other electric. I wondered how the electric/electronic control worked.

[billthekat]

i call it an idle air controle valve....cause thats what they call the part on a newer car that does the same function. and it has coolant running through it to keep it frome icing up...like the throttle body has coolant through it. i had one with a bad casting or something that was actually leaking coolant into the intake wen the valve would open up on a cold start....


but i doubt that's your problem....

what you'r describing to me sounds like a stuck or sticking iac (idle air controle) valve.

i would try replacing it with a low milage salvaged part. (junk yard) as i am unaware of the availibility of this part new.


i replaced mine wen it went horably wrong and all was well. its compleatly plug and play... no special tools needed...


hope i might have been of some help.

[syfir]

Dist cap and rotor did not fix the problem, although rotor did need to be replaced soon. I'm not sure if this is related, I bring it up because of the coolant hoses on the ISC, the thermostat is stuck open. It takes forever to warm up and the heat is not hot. I have not gotten around to changing this yet because the bolt behind the dist is a pain in the butt to get at. Any other ideas before I try changing out the ISC? Also, when the engine shudders, it sounds like there is a lot of backpressure.

[batstiva]

First, watch the language, it'll likely get edited out by a mod. Tho, I feel ya on that bolt. There had to be a better place to put it. lol. When you say the thermostat is stuck open and there is no heat. Is it cold air? Or just not as hot as other cars you have driven. Festivas in general do not produce heat like other cars I have driven. And is it noticeably different now than before the car started acting up?

[GenevaDirt]

^^lol....you were correct Batman....edited. As for the bolt....just pop the disty out and you can get it no problem. But I have done it both ways and have not really had a problem with it....socket and extension....works everytime. Just don't over tighten the bolt when you put it back in because it will strip out the threads very easy. Ask Seth...I fixed his and mine by using a longer bolt and reaching behind the tab it is screwed into and hold a nut in place while threading the bolt in.....now that is a pain in the butt....but it works...lol