High startup RPM-Adjustment?

I have an '89 E-150 with a 351W EFI. When I start it from cold, it revs fairly high for about 10 seconds, then drops down to a reasonable speed.

Is there any way to set the starting RPM lower? I've only had it since April, and I worry about the coming cold weather. I don't like starting a cold engine at high RPM. Any help greatly appreciated. Tom

Reply to
tom graham
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On Sat, 02 Dec 2006 22:02:04 -0500, tom graham rearranged some electrons to form:

No. Idle speed is computer-controlled.

Reply to
David M

That and RPM on startup is supposed to be higher than idle to get the oil distributed throughout the engine quickly. Now it your engine seems to be at WOL on startup, you would need to have it checked out.

Reply to
Matt Macchiarolo

Oops, I meant WOT, wasn't wearing my glasses.

Reply to
Matt Macchiarolo

Your cold start high idle should be between 1300-1700 RPM and drop in a couple of stages over about 90 seconds to near normal idle. This is done because the cold start sequence is in open loop meaning the ECM is running everything from preset data tables on cold start. As the system goes thru it's checkouts and diagnostics, the O2 sensor is being warmed to it's operating temperature by the increased exhaust flow until it can produce feedback. (Your engine oiling system also uses the increase RPM to get the engine lubed. In older engines, the old timers tried to keep the revs down because of the heavy oils of the day taking a while to get to the bearings, etc. The deal now is the lighter spec'd oils gets to the bearings quickly and, the throwoff from the crank as a result of the higher RPM lubes the cylinders and cam lobes more quickly, therby, reducing overall engine wear on cold startup - this is a good thing).

Back to the pint in discussion >> When the ECM senses everything is online and operating and determine the values, it goes into closed loop operation where it is using the sensor values to control the system. If the cold start idle is much outside these values, you may need to clean/have cleaned the throttle body and IAC. Do not for any reason change the adjustment on the idle stop screw. That also controls the voltage reading thru the TPS system that the ECM uses to determine engine load by throttle position which has great influence on things like timing and fuel curves. The idle screw should only be changed following the procedure in the factory manual for you vehicle.

I hope this very basic explanation helps.

Lugnut

Reply to
lugnut

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