1989 gmc s15 v6 4.3 - ecm? - Page 2 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 04-28-2012, 01:30 PM   #11
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that just means something is causing the timing to go all over the place. if it was my truck i guess if the wiring checks out i would buy one knock sensor replace one and see, if not put the original one in the other spot and see. if it isnt either it can be the reluctor in the dist.
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Old 04-28-2012, 06:56 PM   #12
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I've read around and read 4300 ohm resistance on a '94 gm and 8200 ohm on an ls1,

I think if you ohmed yours and had 0 ohms, it'* bad, or if it'* got over 10k, it'* bad.

Might be something a GM tech can tell you.

luck,greg
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Old 04-28-2012, 07:11 PM   #13
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Jeff, you may want to read this Q&A in it'* entirety, Might help.

http://www.answergem.com/cars/q/4697...ault-code-43-t

luck,greg
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Old 04-29-2012, 03:06 PM   #14
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Angry Getting Closer (I think)

I am getting somewhere and I need a little help. I replaced the IAC and it seems to have helped. The one thing I can tell for certain is the vacuum line that goes to this "port" on the engine just to the left and in front of the TBI when connected, the truck runs like crap and stalls. When disconnected it runs at a steady idle. Any ideas what that "sensor" or "switch" is? I can't find it in my Service Manuals and have no idea what it means if it runs better disconnected. See the picture below:
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Old 04-29-2012, 05:21 PM   #15
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the map sensor is the sensor upper left in the pic. if there was something wrong with it it would run bad when plugged in but good when unplugged because the computer goes off programed tables. it may be bad and causing you issues but i dont think it would cause the code you are getting. maybe you have two problems
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Old 04-29-2012, 05:34 PM   #16
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well reading into it it seems running poorly can cause the noise to trigger the knock sensors so maybe thats it.
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Old 04-29-2012, 11:46 PM   #17
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Talk about a wild goose chase! - L (not out loud)

The MAP (manifold absolute pressure) preceded the Mass air flow, From my understanding, it measures intake vacuums relationship to air density, thereby adjusting the fuel mix.

From your sound clip, you're going into a lean or rich stumble, then back out - I guess the could put you into knock area.

The only other bad map I've seen was an old '85 reliant K

I'm cheap, I'd buy one (not mount it) and try it

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Old 05-06-2012, 08:39 PM   #18
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Default Help

So - here I am again... Got all codes cleared. If I unplug the MAP from the circuit, the truck idles fine. I replaced the MAP and it is the same. I am at a complete loss. What would cause the truck to run much better with the MAP disconnected when it is still a good part???
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Old 05-06-2012, 09:10 PM   #19
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the thing must be running on the programed tables with it unplugged masking what ever is wrong. the only thing i can think of is spraying around those fittings on the vacuum line with some carb cleaner if the pitch changes they are leaking
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Old 05-07-2012, 03:48 PM   #20
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Jeff, I agree with jwfirebird, you may also consider that the ecm might need to "relearn" the MAP parameters if it'* been running w/o it.

There'* a million (+/-) methods of "drive cycles) for the "relearn" process, but, I'd drive it around, various speeds, several re-starts, warmed up, and see if it improves.

If not, I'd ohm test the map (engine off) while sucking on the vacuum connection,
(should change with changes in vacuum)

I don't know the values that your looking for, but this may indicate if MAP works at all.

As you step on the gas, loss of vacuum richens the fuel mix

The sound clip almost sounds like the diaphram in the MAP leaks, causing the mix to fluctuate up & down.

A new MAP is $75 or so, I hate experimenting.

luck,greg
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