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Discussion Starter #41
Wait.. just had another look at the pdf. Brake switch on? Not sure about that ECM, but that can cause all kinds of voodoo with OBD2.
I dont know what the brake light reading is referring to because the actual brake light comes on and off when looking at the dash just fine when I use the parking brake. And it doesnt seem to affect the transmission moving between gears or anything else as I assume it would if it were malfunctioning. I will try and do some research to see what that actually means when the scanner shows "brake switch on"
 

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Discussion Starter #42
I think we've found a few dozen smoking guns.

IAT readings would be causing pig rich. VSS shouldn't cause loss of power, but I'm not sure of that. Coolant temp sensor would further the rich problem. Regardless of whether or not its a thermostat stuck open or a bad sensor, it's reporting colder than normal operating and therefore adding fuel.

EGR should be easy to test on an OBD1. Assuming the EGR valve itself is operating well mechanically, just pull the vacuum line and plug the manifold side, or use hemostats to crimp the vacuum line shut temporarily. Then do back to back mountain climbs. If the test keeps the valve closed, and you experience increased power, then something about that EGR signal is incorrect. The ECM is telling the EGR to be open when it shouldn't. (btw... expect a check engine light if you defeat the EGR but it should go away as soon as you re-activate it.)

My shortcoming here is twofold: 1) I'm not sure but what the ECM is trying to bring up temps by keeping the EGR open? and 2) I'm no OBD1 wizard. I kinda skipped that experience. OBD2 and carburetors/distributors are my jam.
I have an electric EGR. It doesnt have any hose that I can pull off or pinch. How do you do a test like you mentioned on an electric EGR? Mine looks like this one from autozone:
 

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Leave the EGR valve in place, but pull the wiring harness off. Without any signal going to it, it will remain closed. No block off plate needed.
 

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Leave the EGR valve in place, but pull the wiring harness off. Without any signal going to it, it will remain closed. No block off plate needed.
Make a blocker plate to test..Those electronic ones can leak even if unplugged
 

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OP.....you need to do a fuel pressure test. Pressure MUST be key on , engine off....26-32 PSI.

Kinda wierd becasue most TBI setups (stock GM ) run about 13 Psi.
You need to use a good gauge .Preferebly a 60 psi range so the reading is accurate. A 120 Psi range gauge may not be the best for accuracy at such low pressures.
 

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I might also add , if the pressure looks good, hook up the gauge so you can drive it.Then replicate the condition that makes it lose power, you know pulling the hill with the boat on, then see what the pressure is doing. When added fuel volume is needed is where you will see pumps show the sign of weakness, even though they may run fine otherwise.
 

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Discussion Starter #50
I have really good news. I unplugged the EGR and it definitely ran stronger! How much stronger.... I really wont know until I hook up the boat or a trailer which is hard to get to right now. I really wish I had access to a Dyno around northern Utah I could tweak this thing on. Anyway, I took it up some decent hills and I can feel a lot less of a bog. By the way, I didn't actually create a block off plate, but I plan to now that I know there is something wrong in that area. I do know that EGR is good. It is only 2 years old and I had a spare I tried as well just in case and nothing changed. I have a feeling the engine coolant sensor or something is giving incorrect data to the EGR and telling it to open and close at the wrong time. Anyway, I am ecstatic that it is working. I have a feeling that there may be some other gremlin in there causing some additional power loss, but the EGR made a huge difference. Thank you all for you kind wisdom! I will keep hacking at it and see what is ultimately causing the problem
 

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Hook up your scanner again and check the coolant temp before you start it. Should agree to ambient air temp.
 

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Discussion Starter #52
OP.....you need to do a fuel pressure test. Pressure MUST be key on , engine off....26-32 PSI.

Kinda wierd becasue most TBI setups (stock GM ) run about 13 Psi.
You need to use a good gauge .Preferebly a 60 psi range so the reading is accurate. A 120 Psi range gauge may not be the best for accuracy at such low pressures.
Hook up your scanner again and check the coolant temp before you start it. Should agree to ambient air temp.
I believe my 95 and the 96 TBI engines had the higher fuel pressures. I know mine does. I did check it last year when I had the old engine in place (same TBI and intake). It wasnt the safest or smartest way to check the fuel pressure, but I put a "T" down at the fuel filter and added in a gauge with a long fuel line to read the fuel pressure with a hose that came up into the cab 😬 so I could read it while driving in all conditions. I actually took it on a trip and watched the gauge while pulling and it never budged. The pressure held steady at all times. I have an adjustable pressure regulator at the TBI and have it set at 32 PSI. So I am on the higher side of that range. Do you think bringing it down would help?
 

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Have you ever changed the O2 sensors? Treat em like a spark plug on that old beast.
 

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Discussion Starter #55
Have you ever changed the O2 sensors? Treat em like a spark plug on that old beast.
The o2 sensor is new. I changed out a whole bunch of engine electronics when I had the old engine in there because it was giving me this lack of power issue.
 

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Discussion Starter #56
Hook up your scanner again and check the coolant temp before you start it. Should agree to ambient air temp.
I checked the scanner after it had been sitting all night and all day. It is reading 57 degrees which is right on with the air temp right now.
 
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