high idle - S-10 Blazer 4.3 Vortec CMFI - S-10 Forum
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post #1 of 4 Old 02-03-2002, 10:25 PM Thread Starter
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high idle - S-10 Blazer 4.3 Vortec CMFI

can anyone help me diagnose high idle problem on 93 S-10 blazer 4.3 vortec CMFI.

I happen to have a GM Tech 2000 diagonostic unit.

Continue to receive code 35 IAC even after replacement of IAC with new one.

lately, engine idles at approx. 1,100 rpm. Tech 2000 will increase rpm but will not lower rpm, seems to be at limits of low range adjustability.

only change recently has been addition of light weight flex fan and removal of fan clutch but do not believe this is causing/contributing to high idle.

Also receiving code 45, O2 sensor - rich exhaust. Have recently replaced O2 sensor with new one. Continue to receive code 45.

Is there a manual idle adjustment anywhere ?

any help/advice greatly appreciated please.


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post #2 of 4 Old 02-03-2002, 10:48 PM
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You sound pretty technically versed but sometimes the simplest things are often overlooked. Have you disconnected BOTH battery cables for more than 1/2 hour?. Try this and see what happens...Would not clear my service light on my truck till both battery cables were disco'd. Other than that thats about all I can figure being as you say you replaced the parts that are coding bad but didnt mention clearing the old codes...Let me know how you make out...
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post #3 of 4 Old 02-03-2002, 11:40 PM
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You have a vacuum leak or the EGR valve is stuck open.
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post #4 of 4 Old 02-05-2002, 02:19 PM
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High idle sounds like a...

vacuum line is loose or broken. Check the small line at the back of the manifold near the distributor that T's off for the vacuum canister, cruise and heater controls.

The running rich could be your first warning that the regulator on your CPI unit inside the manifold is starting to leak (common problem with the CPI engine). If it is you'll soon get code 32 EGR, very stinky exhaust smell and rough idle as well. I replaced mine at 147,000 miles with the new improved design unit p/n 17113673 for $265. PM or email me if you need more info.

You can also clear the computer codes by removing the ECMB fuse. I think it is number 9, bottom left of fuse panel.

'94 Jimmy, 4.3/CPI, CFM Stage III heads, Ferrea stainless valves, Comp 1.52 rollers & ovate wire springs, ARP studs, K&N Gen II & CAI, Stage II chip, 160 thermo, Dynomax SS Ultra-Flow catback, Zexel LSD, 3.42, Shift+, electric fan, UD crank pulley, Jacobs w/ Ultra-Coil, Taylor Spiro-Pro, Rapidfires
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