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Old 01-03-2003, 07:21 PM
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Post Cold run/fuel enrichment for '94 Chev 350?

My experience is dated [spell old man] to carburated engines, which I understand well.
My question is in regards to what would otherwise be known as the choke system on my '94 Silverado w/350 throttle body injection. Im suffering low [700rpm] idle speeds from cold starts.Strangely enough however, cold performance is very good, no stumblimg etc.
What enriches the fuel mixture for cold running apps & is there an equivelant to a fast idle screw?

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Old 01-03-2003, 09:40 PM
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THE COMPUTER ENRICHES THE FUEL FROM A ENGINE TEMP SENSOR AND IDLE IS CONTROLED BY A ISC SOLONOID 9V POWER SOURCE WHICH WILL BE LOCATED ON THE THOTTLE BODY W/WIRES BUT BEST BET WOULD BE TO GET A CHILTONS BOOK FROM A LOCAL PARTS STORE.
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Old 01-03-2003, 09:51 PM
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You are probably going to be looking at a couple of things here Fly. I would suspect the idle air control valve, which is on the side of the throttle body. This is basically a controlled vacuum leak regulated by the ECM {Computer}, a quick way to check it's function is to just unplug the thing while it's idling, if there's no change, then chances are really good that it's not working. You can also remove the air cleaner and look down into the throttle body, and you'll see a small passageway, down in the passageway is a needle valve, that's the end of the IAC motor, and watch for movement, if it doesn't move, veryify the circuit and ground to it, if you have all of these, it's probably bad.
I don't really think you've got a fuel metering problem, it really sounds like Idle air control to me. The IAC, under normal conditions, will "flare up" during cold start, and keep the idle speed up until the system warms up, then it will slowly decrease idle speed.
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Old 01-04-2003, 07:52 AM
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I would suggest finding out exactly what your cold idle should be at for your vehicle. Fuel injected engines do not require the high rpm's that carbed engines do because of the ability of the computer to constantly fine tune the fuel ratio for all conditions. My truck flares up as NAIRB described during initial start-up but within a few seconds drops back down to a pretty normal idle. You need to find out how much the computer is commanded to increase your idle and for how long. If it doesn't bog or hesitate there may not be anything wrong with her. If she is supposed to be idling higher the the idle circuits (ISC,IAC,etc. depending on your set-up) need to be checked as mentioned already.
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Old 01-04-2003, 08:54 AM
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Thank you all, good info to get started with. I'll study up on cold idle speed & test the air control valve as suggested.
FlyB58
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