What causes an engine to stall at idle but run fine over 1000 RPM?
Your throttle body is probably dirty,The throttle body has a hose from the air filter housing attached to it,the throttle body is attached to the intake phlenum.Take the hose off(its rubber with a clamp on it).Do this with a cold engine, NOT RUNNING ! spray some carburetor cleaner inside the venturi and scrub it with a toothbrush,on the side of the throttle body there is a place where a cable goes into,twist the direction of cable to open the throttle plate(inside the throttle body),and continue to clean.Now put it all back together.What happens over a period of time is the Throttle body gets clogged with carbon and cannot breath at idle, the throttle plate when close(at idle)has a very small air gap and cant breath when dirty.If this does not cure your problem,then you will need to consider having your ais motor check.ais= automatic idle speed motor.For this you will have to take the throttle body off to replace it and the screws have been installed with locktight and are tricky to get out. ,I did not know what year or make of car, but its a common problem since the fuel injectors took the place of the carburetors.
- ** Be careful that any cleaners used are for Fuel Injected systems and are O2 sensor safe. Some Carburator Cleaners can damage FI components.**
- Spraying a throttle body spray cleaner, such as one sold by STP, to clean the throttle body, then starting up and revving the engine, may be enough to dislodge the carbon deposits and material blocking the airway. The original poster's solution is the cheap and easy way to handle this problem of low engine RPM causing stalls. Try it first, it is a fast fix, and it worked for me, causing my engine RPM to go up above the stalling level when my car was idling at a stop sign or red light.
I had this problem just two days ago. When the rpm goes below 1000 it stalls; visible black smoke is also observed at the exhaust when it's rev up. Try changing the air filter as this might be clogged up causing an inefficient air/fuel ratio. When there's not enough air going into the system complete combustion is not achieve causing this problem. Good luck. Pls let me know if it solve your problem.
(addition by LucheLibre) My 87 Jeep Wrangler had the same problem. Did some research and found that older jeeps use very thin idle tubes mounted in the venturi. These can easily become clogged and fuel will back up and come out the main nozzles, causing the Jeep to run too rich and die. The solution is quite simple. Pull the air cleaner housing and choke plate off--remember to keep an eye on how the choke linkages are connected to the carb--unscrew the venturi and pull it out. You can't miss the tubes. Run a long, very thin wire or pin down the tubes and then reinstall everything in the reverse order. Your Jeep will literally be good as new. If the same problem comes up again, then your float bowl is junky and clogging the tubes again. Clean the bowl and change your fuel filter.
I've never known an "automatic idle speed motor" to be considered a throttle position sensor. An "idle speed motor" is just another name for an "idle air control valve" or "IAC". I've seen this concern many times. Most of the time it was caused by gunk becoming lodged inside the IAC passage. That's one of the easiest things to inspect at least.
Another possibility, a stuck open or sticking EGR valve would also cause those symptoms.