I have a 1987 plymouth horizon runs great except at idle it runs hi for about a min or two right after i start it then it idles right back down. but then puts like its guna stahl out. i found a screw

SOURCE: Engine runs rough after about ten minutes /idles really low

Just trowing some suggestions out there, but, I would check the idle air control valve (solenoid) or the throttle position sensor. If they check out then my last guess would be the map sensor or the vaccuum to the map sensor. Hope I was able to help. Best wishes.

SOURCE: 1990 Plymouth Horizon America troublre

The speedometer went out at 50,000 miles. The head gasket blew at 125,000 miles. I bought this car new when I started college, and it was the best front-wheel drive car I ever owned. The speedometer went at about 50,000 miles. I traced it to the printed circuit board, but Chrysler didn't carry the part, so I guessed my speed based on what gear I was in and my tachometer reading.

SOURCE: Engine Races

sounds like a faulty idle speed sensor

SOURCE: Car shuts off

I would check the Idle Air Ctrl. valve.if not opening when coming to a stop eng will starve for air cause air is not bypassing the throttle plate when the plate is closed

Mike Butler

• 6674 Answers
• Posted on Oct 12, 2010

SOURCE: We have a 91 Plymouth

Remove the A.I.S motor and give it a good cleaning (especially the pintle -pointed end ) with throttle body spray cleaner, as well as the port you remove it from, then re-install and try it. That will usually cure it, and if it starts to happen again, replace the A.I.S. motor. Doesn't hurt to give throttle plate and area a spray while your at it.