93 Ford Escort LX idling rough

[200PlusClub]

My 1.9L car has started idling rough and sometimes stalls out. Sometimes it revs at 2000 rpms then comes back down, sometimes it revs at 500 rpms and stalls out. Sometimes the rough idle disappears altogether and it revs normally in idle at 1000 rpms.

I have tried the following:

1) Used carburetor spray cleaner on the butterfly valve and throttle body. I was given this advice from a Ford dealer, then I noticed a sticker on the throttle body saying that the internal coating can be damaged by carb cleaner, so hopefully I haven't done any major damage! This actually did help but only for a short while, then the rough idling returned.
2) Replace air filter but this made no difference

I am debating if I should try to get another throttle body from the junk yard. I am not sure what else it could be - maybe I should get another air flow sensor from the junkyard as well?

[szigatti]

My 94 did that for a bit. Take a look at all the vacuum hoses, it could be a leak.

and if it is the throttle body try just cleaning the iac. it looks like a solenoid on top of the tb. two blots takes it off, clean and lube it. the iac can also be replaced cheaper than a whole new throttle body.

[dougand3]

Auto parts stores and even wally world now have "Air Intake and Throttle Body" Cleaner. Like szigatti said, pull that IAC and spray it good, light oil on the center pin and spray good into top of TB where the IAC connects....lot of carbon in there.

[wtousand]

Originally Posted by 200PlusClub

My 1.9L car has started idling rough and sometimes stalls out. Sometimes it revs at 2000 rpms then comes back down, sometimes it revs at 500 rpms and stalls out. Sometimes the rough idle disappears altogether and it revs normally in idle at 1000 rpms.

I have tried the following:

1) Used carburetor spray cleaner on the butterfly valve and throttle body. I was given this advice from a Ford dealer, then I noticed a sticker on the throttle body saying that the internal coating can be damaged by carb cleaner, so hopefully I haven't done any major damage! This actually did help but only for a short while, then the rough idling returned.
2) Replace air filter but this made no difference

I am debating if I should try to get another throttle body from the junk yard. I am not sure what else it could be - maybe I should get another air flow sensor from the junkyard as well?

I think you have a classic case of vacuum leak and it can even be reasoned out.

When the car is cold with a vacuum leak, it will idle fast because it gets a rich mix when cold and can handle a bit more air (but it will idle faster than normal). When the car warms up, it may idle closer to normal, at least for a few seconds right after you pull up to a stop sign and release the throttle. Within a few seconds though, the computer will reset the mixture to an extreme lean* condition (for purposes of reduced pollution) and then the engine will either idle very low or stall. If these are your symtoms, the VOILA ...you have a vacuum leak. Even if you car doesn't always stall ...yet.

When the car is cold and idling fast under these conditions, you will have the most amount of vacuum. At that time you will often be able to actually hear the leak as a hiss. Like most engine sounds, it can be pinpointed easier by having a small diameter hose about 3 feet long ready to go as a stethoscope. A likely candidate is the weak, thin rubber elbow that connects the PCV vent hose to the intake plenum.

* It is interesting to note that in the early days of carburetors, all idle mixes were set rather rich to prevent stalling under a variety of conditions. Later pollution carbs tried to lean this mix with random drivability success. The eventual shift to computer controlled injection allowed the mix to be changed to a leaner condition under extended idle. This helps quite a bit with pollution caused by vehicles which are often left to idle. Keep in mind that a rich mixture doesn't ever have enough oxygen and the combustion produces more carbon monoxide (CO) instead of less harmful carbon dioxide (CO2), besides particulates like soot. Tailpipes aren't so black anymore and neither is the air. Long live earth.

[Davescort97]

Replace the PCV valve.