88 Carb Festiva won't idle.

[5.0zone]

My Festiva all of a sudden doesn't want to idle any more. I runs fine down the road but it just doesn't want to idle.
I turned up the idle speed for now just so I can continue driving it (1500 - 2000 RPMs).

Things I've tried so far:
Spraying out the carb with carb cleaner (just what I can get to with it on the car)
Running Seafoam through 2 tanks of gas
Checked for vacuum leaks - none found
Changed fuel filter

Is there some valve or solenoid that controls the mixture at idle? I've had problems with the deceleration valve sticking before on this car and my other 88 Festiva, but that doesn't cause idling issues.

I thought about removing the idle mixture screw and flushing it out. But couldn't figure out how to remove the cover over the screw.

No, I'm not interested in converting this car to a Weber right now. Nor do I won't to go through the hassle to convert it to EFI.

Thanks in advance for the help!

Jeff

[tooldude]

My opinion, but do not change the mixture screw setting which is factory set and capped off for good reason. Feedback carbs are not the same animal as the old carbs. The feedback system with sensors should be handling things & adjusting air/fuel ratio. Make sure the throttle plate is closing sufficiently, it has the largest effect on idle. Check compression, and for exhaust restriction. Carby owners need a hand vacuum pump for checking the several vacuum diaphrams that could be leaking, especially the distributor dual diaphram affecting timing. Check for hardened vacuum hoses, connected but not tight-be gentle on plastic connectors.

[WmWatt]

You can remove the air filter and spray all the external linkages (choke, throttle) with carb cleaner.
Misting the engine while idling is supposed to reveal any vacuum leaks by stalling.
There's a temperature-controlled gate in the air cleaner which should open freely.
I'd clean the EGR valve, just for fun. It's so simple to do.

[tooldude]

Again, just my opinion and way of doing things, believing the vacuum hoses and devices that need to hold vacuum have the highest probability for failure. I like to get them eliminated, as a vacuum leak may affect the MAP sensor or dual chamber distr. advance, and could be multiple tiny leaks. WmWatt makes a good point about the EGR valve which for me is in the next tier of checks. Looking at your mileage posted, it is a good possibility it needs cleaning. If you don't have a vacuum pump, it's a relatively quick and easy thing you could alternatively check. Take off the screw and small tube at the bottom as the small opening tends to close off first (It may take soaking in penetrating oil). Check for the passage in the manifold being choked off also.

[tooldude]

I was having way too much trouble with posting from my phone in the first post to answer your question. The carburetor has a "can" on it with 4 vacuum hoses connected on top called a Feedback Carburetor Actuator (FBCA). Inside it are 2 needle valves called Air Bleed Control Valves (ABCV). In Ford manuals you'll find it referred to by both names but it's the same device. It works similarly to the mixture control valves on other feedback carbs. It controls only air which is mixed with the fuel in the passageways. It's controlled by the ECA which is dependent on input from the O2 sensor, MAP sensor (Ford calls Boost sensor), RPM signal, ECT sensor, ECT switch (on radiator bottom), & Idle switch (by carb throttle adjusting screw). This can only operate when the system goes into closed loop. Before that, the ECA is operating with programmed values. So, if your engine is not idling when it's started up cold, apparently none of these are involved. Could you lay out the process and conditions when that occured, was it gradual or sudden?

[monkeykiller1996]

i had the same problem mine would hardly idle hanging on for life at about 350-400 rpm (dieing out sometines)it ended up being a vacuum leak i only found the leak after getting pisssed off enough and using the vacuum chart to trace every vacuum line and even if its not a vacuum line leaking it could be the gaskets under the carb or the intale manifold gaskets also the guy above me ^^^^ knows what hes talking about :ia:

[Movin]

"I thought about removing the idle mixture screw and flushing it out. But couldn't figure out how to remove the cover over the screw."


It sounds like you are on the right track , use the carb clean and compressed air on the little holes visible below the choke plate. It can be tough getting something out of the idle circuit, those are the smallest passages and the have to go from the fuel up toward the top, then all the way down below the throttle plate, passing through gaskets as well. The most effective is removing the needle and blasting back into the hole, but it is hard to do on the car.

Some times just reving the engine up then slamming the choke plate shut by hand will clear the passage too.

[tooldude]

The whole time I was writing I kept thinking, what if it's the idle circuit...what if it's that idle circuit...what if it's not? I still believe it's best to start with the vacuum controls to have a solid base to work from. I'll bet there is hose that should be replaced even if there are no leaks, so there is still knowledge & benefit for the effort. There could be faulty EGR or canister purge too. He did run 2 cans of sea foam, at least. What if he jumps into the carburetor, which may be tricky, and the issue is still not resolved? The issue is right where it started with the complication of not knowing if there is still a carb problem, plus having had to buy a carb kit. That's 'rather aggravating'. Then there are mechanical possibilities.....is it really fun to work on cars?, I'm forgetting. That's my 2 cents. Maybe that should be my forum name, anyone have it?

[Movin]

It is fun or we would be building woodstrip sailing canoes and discussing why an unexpected swim took place! Or??

Back to this, if the car can run until the choke is open he can turn the idle speed down toward normal until it runs poorly but still runs. Carb cleaner with the little tube installed can be whiffed at the open choke plate. The idle should smooth out and increase in rpm if it is running lean. If this happens a whiff directed at the base gasket, different suspect hoses or any spot including the brake booster should cause the engine to momentarily smooth out the same way. If nothing shows up except the indirect fumes getting in the carb then it could be assumed the idle circuit is plugged or if it is equipped with the idle circuit fuel cut that it could be closed all the time. Mine is an 88 but when I was wrenching for ford and doing carbs all the time it seems that some had it and some did not. Mine does not.

[tooldude]

I thought he had done basically what you're saying Movin, but rereading, now I'm thinking maybe not. So 5.Ozone, there is the excellently laid out procedure from the voice of experience.

[tooldude]

So, did a little research. Ford named that solenoid Slow Fuel Cut Solenoid which had me thinking it only cut fuel to the slow port, but I see in the manual how the idle port actually is fed from the same passage and could be cut off as you were saying Movin. Also, do you know if it has a rubber tip which could separate and lodge in the passage? If that solenoid is on your carb 5.0 you should check for key-on voltage getting to it & proper operation.