Need help with an 88 TBI 350. IAC Problem - Pirate4x4.Com : 4x4 and Off-Road Forum
 
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Old 02-17-2011, 11:10 AM   #1 (permalink)
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Question Need help with an 88 TBI 350. IAC Problem

for some reason, the IAC on it keeps going in and out. sometimes it'll work, sometimes it won't. tried a new IAC, another computer, and the wiring checks out good. even with the new IAC and computer it does the same thing. works for a while, stops working, then it starts working again. anyone have any ideas why?
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Old 02-17-2011, 05:19 PM   #2 (permalink)
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possible vacuum leak or fuel pressure issue if your wiring checks out and you put on a new IAC valve and computer
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Old 02-18-2011, 07:05 AM   #3 (permalink)
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smoke tested the motor for vac leaks, none found. fuel pressure is consistant at 15 psi.

i have a feeling it may be something loose in the connector, in the wiring harness. it's a new harness though, from howell, so it "should" be good. but that's really the only thing that makes any sense since it does it with a new iac and new ecm. i'm thinking it's some type of intermittent connection maybe?
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Old 02-18-2011, 09:08 AM   #4 (permalink)
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time to bust out the volt meter reader and do some probing
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Old 02-21-2011, 07:06 AM   #5 (permalink)
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yup, did a little this weekend. couldn't find anything intermittent. this is weird...
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Old 02-21-2011, 07:15 AM   #6 (permalink)
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Check to see if a pin is pushed back on the harness.
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Old 02-21-2011, 07:16 AM   #7 (permalink)
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good idea.. i'll check.
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Old 02-21-2011, 07:56 AM   #8 (permalink)
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Grounds, or lack there of, can cause gremlins. Is there a complete ground path between the body, frame, and engine?
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Old 02-21-2011, 08:01 AM   #9 (permalink)
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grounding should be adequate. grounding straps from the motor to the frame, body mounted/grounded to the frame. any others i might be missing?
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Old 02-21-2011, 10:18 AM   #10 (permalink)
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Engine grounds to ECM? There are a couple of common ground points at front of the engine that have 2-3 ground wires each, that go back to the ECM. Also, just because the wires "look" good, doesn't mean they are electrically good. If I were chasing the problem you describe, I'd remove each ground, and properly clean and reinstall it. Your problem sounds like wiring.
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Old 02-21-2011, 10:22 AM   #11 (permalink)
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i will certainly do that. thanks for the suggestion.
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Old 02-21-2011, 03:02 PM   #12 (permalink)
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Although there are ground straps as mentioned, you should check your grounds at the t stat housing. Mine were corroded underneath but seemed to be fine visually and cost me a lot of time doing pin outs, and trying known good parts.
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Old 02-22-2011, 06:14 AM   #13 (permalink)
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i'll check em, thanks for the tip.

i appreciate all the tips guys, thank you.
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