LT1-LT4 Modifications 1993-97 Gen II Small Block V8

idles too high and miss

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Old Jan 2, 2012 | 02:53 PM
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Default idles too high and miss

Hey guys. I'm working on my 95 TA with 148,000 miles. I bought it a year or so ago with a bad trans. Got the trans fixed and I'm really wanting to start driving it but it now has a miss. It idles around 1200 and I can hear a miss when it's idling. When driving it jerks a little at low RPM- once it gets up to a little under 2000 it runs great and pulls hard. There is no check engine light on. I listened to the injectors and one wasn't clicking so I replaced it. Ran better but still had a miss. I've also replaced both O2's, new air filter, cleaned MAF, new plugs and wires (wow that passenger side sucks!), fuel filter, seafoamed it, and checked for vacuum leaks. Kind of running out of ideas besides the opti. Anything else I can check?
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Old Jan 3, 2012 | 07:24 AM
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I would check to see what the TPS voltage is. Someone else might have been messing around and tried to change the idle or something. Next make sure the intake elbow couplers are nice and tight no leaks. MAF tight as well. Check all the hoses on the intake for cracks ect. Is the brake booster hose secure and leak free?. Most common cause for hi idle is a vac leak or loose intake clamp. Of course the IAC could be going out as well so it should be checked as well
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Old Jan 4, 2012 | 06:17 PM
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Thanks for the suggestions. TPS is .58v at idle. I replaced a bunch of the vacuum hoses today and cleaned out the TB and IAC good. The car now idles at 850-875 rpm with a target of 800. IAC seems to be working fine. I can still hear a slight "pop" randomly when the car is idling. Can't feel a miss though. When driving in a higher gear (5th or 6th) and it's given more load the car jerks and runs real rough. Once it gets up over around 2000 it seems to run great. Is there any other way to check injectors other than by listening to them? The replacement I got from NAPA is very quiet- nothing like the clicking from the rest of them. Also if the EGR is bad wouldn't it throw a code?
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Old Jan 5, 2012 | 02:11 PM
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Any idea what the injector pulse should be at idle? One side is 2.9ms and the other is 3.4ms. Maybe bad injector?
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Old Jan 5, 2012 | 02:43 PM
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I'm going to go out on a limb here blame your opti ....148K is pushing it (I'm on my 3rd one with 150K)...has it ever been replaced completely? The symptoms seem ignition related rather than bad injector(s). Good luck troubleshooting the opti/replacing it!
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Old Jan 5, 2012 | 03:08 PM
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lol I think that's probably what it is too- just don't want to throw away all the $ on a new one and that not fix it. I don't know if it's the original or not. I've done all the troubleshooting I could find for the ignition and everything tests good so the opti is the only thing ignition wise left. I was pulling injector harnesses off one at a time to listen for a drop in RPM and the one I replaced recently doesn't drop the RPM at all.... the rest of them do.
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Old Jan 6, 2012 | 09:35 AM
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could just need a cap and rotor since those are wear items that no one ever changes on these cars. could be corroded or something, or could be a weak coil pack
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