Test IAC
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Is there a way to check pulse, the reason i'm lookin at the iac is that with truck running i unplug it and no difference,also unplug electrical from map sensor makes no difference. truck used to run decent except for surging idle after warmup as time went on it burned richer and richer now it runs like crap, cutsout,no power. there is no scrader valve to check fuel pressure and the plug to hook scantool to is long gone before i got the truck although there are a couple wires laying there.
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It actually isn't an Idle Air Control valve, but an Air Bypass Valve. This describes how it works: http://www.tomco-inc.com/Tech_Tips/ttt23.pdf
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From: Northeast, OK
Yes, as seen here:
- Page 61 here shows the Throttle Air Bypass Solenoid Valve: Electronic Engine Control - ???Gary's Garagemahal
- Page 60 at the same link shows the power that comes from the EEC Power Relay and Fuse Link Z
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Thank you sir, guess i'm to dense to understand, if i am understanding power for tab comes from eec relay but i still cant figure out if tab should have power when key is turned on or not, my interpretation is that it should and the ground is what pulses the power.
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Thank you sir, guess i'm to dense to understand, if i am understanding power for tab comes from eec relay but i still cant figure out if tab should have power when key is turned on or not, my interpretation is that it should and the ground is what pulses the power.
It also sounds like your throttle adjustment screw is too far in, the butterfly is too far open. It should barely idle when the IAC is unplugged. If it's not working at all, the engine should still barely idle.
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From: Northeast, OK
You probably shouldn't call it TAB as that acronym has already been taken. Look on Page 60 in the upper right where it says "Thermactor Air Bypass Solenoid (TAB)". So, lets call it TABP like Tomco?
Anyway, look at Page 65 on the left side. The second paragraph says the EEC Power Relay supplies power to Circuit 361 in Start or Run. And, since 361 powers the TABP, it will have power with the key on, meaning Run.
Anyway, look at Page 65 on the left side. The second paragraph says the EEC Power Relay supplies power to Circuit 361 in Start or Run. And, since 361 powers the TABP, it will have power with the key on, meaning Run.
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Wiring problem makes sense, test lite grounded to battery and no power to tabp harness, would also explain why unplugging map dosent affect it. thank you very much sir, tomorrow i'll start checking wiring.
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I found that if i wiggle the probe from voltmeter around inside of harness pigtail to tabp i got intermittent voltage, i sprayed electrical cleaner inside a few times and now have steady voltage. i believe i have a bas tabp, i am checking it with an ohmmeter and if i am doing this correctly it apparently is bad. i have a cheap meter,when i set it to ohms no matter what range it show a number 1 on far left and when i touch probes together i get 0. Test from either prong on tabp to solenoid body and meter stays on 1, test across both tabs and it stays at 1?