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when I swapped in an NV4500 for the 700 in my '87K5 TBI, the GM parts guy sold me a manual PROM. Questions:
1. differences between AT and manual PROMs?
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Generally, a stick prom (all else being equal) will have less timing, as the tq. converter in an auto equipped truck can cushion things, allowing a more aggressiving timing curve. Additionally fuel & sometimes other parameters are different.
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2. Is the PN switch fed to the ECU on my '87? (it stays in Park now all the time, &runs OK)
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Unhook it.
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I'm not sure what the situation is on your 87 when you say it stays in "park". But the ECM does use the signal from the Park/neutral switch. Generally it is better to leave the P/N switch ungrounded all the time (as if it were in Drive)
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Correct, this is how a stick harness is setup.
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some aftermarket harnesses ground the P/N signal all the time.
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True, which doesn't "fix" anything. It just suppresses the SES lamp.
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ok, really really dumb question since i'm going to start building a rock buggy in a few months with a 4.3tbi and a 465. Where does a manual tranmission tbi engine get a vss signal from? I assume from earlier posts that the prom in the ecm is different too??
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The majority of ECM equipped 80's cars and trucks used a 2 pulse VSS in the speedometer head. The wheel spins w/ the speedo, and the pickup for it has 3 wires. I don't know what years trucks got them, but 81-90ish cars w/ mechanical cables did.
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You can add the VSS to any system with a chip made to accept it
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Okay all this "VSS can be added" to a system which never came without is a CK5 fairy tale. Considering every ECM car got a VSS, I want PROOF of the LochNess VSS-Less TBI system that has been talked about on here.
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I have no problem putting on a VSS. Can I use a factory GM one or who has the best VSS in the aftermarket that has the easiest install and least problems. Thanks again for all of the advice. /forums/images/graemlins/thumb.gif
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Sure. You've a 79? I think an 80's speedo head w/ the VSS built into it would be your easiest and most likely economical way to go. I've never seen that style of VSS fail.
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Who is misleading anyone? Read my post. "FWIW, and not trying to start anything," I was only bringing up that I had not had problems when not using the VSS input.
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You had problems, you just never had glaringly visible to you problems. That's why you are misleading "a collective us."
There's plenty of people who wouldn't notice a plug wire loose on a V8 and keep on driving it. That doesn't mean that they didn't have problems. That just means they don't know any better.
Let's more onwards and upwards from the fairy tale VSS-Less TBI and other such "stick it in park so it won't throw a light" cockamamie and get some trucks running RIGHT, as opposed to GOOD ENOUGH.
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I did not tell anyone that VSS was not needed. I hoped it would spark further discussion, which it did, and azblazor provided a positive, helpful post to explain the importance of VSS. Try doing the same.
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I could come on here and make stuff up, coddle some people, tell them their swap is "fine" when it's not. I prefer the truth.
thanks
Matthew
