Engine Mechanical problem
1990 Dodge Spirit 4 cyl Two Wheel Drive Automatic 88K miles
Took my car to a mechanic due a rough idle situation. He replaced MAP sensor, distributor pickup, spark plugs, and fuel filter, none of which solved the problem. He then somehow raised the factory idle form the correct 750 rpm to 1000+ rpm, which only diminished, but did not solve the problem. I finally figured out the engine needed a new EGR valve. The engine now idles smoothly, but, of course, it has a too high idle speed. How do I lower the idlel speed? Is there some kind of idle speed screw l; iek the older carburetors had? I asked the mechanic, but he told me it was kind of an involved process, and preferred I bring the car back to him and waste more of my hard earned money!
Too fast an idle speed. If an engine without computerized idle speed control is idling too fast and refuses to come down to a normal idle speed despite your best efforts to back off the carburetor idle speed screw or air bypass adjustment screw (fuel injection), air is getting past the throttle somewhere. Common leak paths include the carburetor and throttle body gaskets, carburetor insulator spacers, intake manifold gaskets, and of course, any of the engine's vacuum fittings, hoses and accessories. It is even possible that leaky O-rings around the fuel injectors are allowing air to leak past the seals. Another overlooked item can be a worn throttle shaft and a defective idle speed speed control motor/valve stuck in the extended (high idle speed) position/throttle position sensor. Also the throttle plate could be binding in its bore and kinked accelerator cable, coolant temperature sensor might not be operating properly misleading the computer that the engine is still cold and computer throwing fuel at it raising the idle speed.
March, 29, 2009 AT 1:59 PM
Where is fuel injection (TBI type, non turbo engine)
adjustment screw you referred to? That may be what the mechanic adjusted when he increased the idle speed to mask the rough idle. Remember that, before he worked on the car, the idle speed was correct!
March, 29, 2009 AT 2:19 PM
Did he fool around with the ignition timing? See below Info
March, 29, 2009 AT 2:32 PM
He would not tell me exactly what he did. When I talked to him yesterday about how to reset the idle he had raised, he would only say that it's a bit involved and that I should bring the car back to him this Wednesday. I don't want to spend any more money on this man, since it was I, not he, that determined it needed a new EGR valve to correct the rough idle, not all the useless and expensive things he did! But now it looks like there is no easy way to simply lower the idle to factory spec. So I will probably be stuck bringing the car back to him. So much for saving money!
March, 29, 2009 AT 2:47 PM
Sir-Try doing below for the computer to relearn itself. He probably disconnected the battery.
March, 29, 2009 AT 4:43 PM
Will try your suggestion and let you know how it works out (successfully, I hope!).
March, 29, 2009 AT 6:51 PM
I tried this method four times without success. It certainly sounded like a good idea. Do you have any other suggestions?
March, 30, 2009 AT 7:10 PM
Does your lack of reply to my last email mean you have no further ideas?
March, 30, 2009 AT 8:58 PM
Sorry didnt get back quick enough to respond
Look around the TB unit for stopper screw that will open and close the throttle plate without the use of the accelerator cable/linkage there's has to be something there to enable to drop the idle speed.
Check what's happening with the automatic idle speed motor test as per the manual.