Gbcinvisalia
TYF Newbie
- Joined
- Jan 8, 2015
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New to the forum. Have found a lot of useful info searching but looking for some more insight.
Bought my 98 a couple weeks ago. Perv owner stated truck had miss because it needed new cap and rotor. He was correct. Replaced them both. Truck had new plugs and wires but plugs were boschs so I scraped those for new acdelco iridiums. Miss didn't go away at all. Ses light is on I don't have a reader though. When the truck is cold in the morning it runs perfect. So I unplugged the ect sensor and truck ran perfect even when warmed up so I replaced that as well. Didn't change the miss. Fuel pressure is within specs and fires right up everytime I turn the key so I ruled out injectors and fpr. So I started probing with my multimeter. Truck doesn't shift into overdrive much and first gear seems to shift late so I figured tps. There's no fluctuations in the rise of voltage it's smooth so I don't think its that now. But what I fid find was the 5v reference wire is reading 8.5-9v when it should be 5. And the signal at wot is about 7v When the max should be no more then 5v. It's at .9-1.0 at closed throttle. I probed the wire directly off the pcm and its still at about 9v. With all my searching all I could find was talk about pcm grounds. I found 1 off the thermostat it's still good no corrosion so I cleaned it anyways no change. Truck runs perfect minus the late shifts still if the map or any other sensor is unplugged. But if everything is like it should be it misses and pops out the exhaust after 1000rpm under load. Idles perfect all the time. I'm leaning towards a bad pcm but the higher voltage is stumping me. Any input would be appreciated.
Bought my 98 a couple weeks ago. Perv owner stated truck had miss because it needed new cap and rotor. He was correct. Replaced them both. Truck had new plugs and wires but plugs were boschs so I scraped those for new acdelco iridiums. Miss didn't go away at all. Ses light is on I don't have a reader though. When the truck is cold in the morning it runs perfect. So I unplugged the ect sensor and truck ran perfect even when warmed up so I replaced that as well. Didn't change the miss. Fuel pressure is within specs and fires right up everytime I turn the key so I ruled out injectors and fpr. So I started probing with my multimeter. Truck doesn't shift into overdrive much and first gear seems to shift late so I figured tps. There's no fluctuations in the rise of voltage it's smooth so I don't think its that now. But what I fid find was the 5v reference wire is reading 8.5-9v when it should be 5. And the signal at wot is about 7v When the max should be no more then 5v. It's at .9-1.0 at closed throttle. I probed the wire directly off the pcm and its still at about 9v. With all my searching all I could find was talk about pcm grounds. I found 1 off the thermostat it's still good no corrosion so I cleaned it anyways no change. Truck runs perfect minus the late shifts still if the map or any other sensor is unplugged. But if everything is like it should be it misses and pops out the exhaust after 1000rpm under load. Idles perfect all the time. I'm leaning towards a bad pcm but the higher voltage is stumping me. Any input would be appreciated.
