Random power "leveling off" issue

Strokersace

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So not sure whatever up with my 97. Just got back from a 1400 mile trip pulling the horse trailer. Truck ran great for the most part till the way home. Would get up to speed, 60 ish mph just fine then just seemed to level off on power. Egts would not climb over 1050 to 1100 and couldn't get any speed over 70. It was running like a bone stock 90cc injectored obs with no chip. Except have the mods in my sig and with this setup and stock programming, it runs like a chipped stage 1 injectored rig. Pulls hard, has plenty of ripened normally and will easily push past 1200 egts when pulling (although that's my personal limit to start backing out of it). Tried shutting the truck off, restarting, nothing changed.

I remembered a couple of years ago that I had a similar problem and it ended up being a had MAP sensor. Last year when I redid things under the hood I replaced every sensor, including the map, with a brand new one. Still I checked to see if that was the culprit and unplugged it. Still no change now, whereas that helped me diagnose the similar issue a couple of years ago.

So when I stopped down the road a ways for fuel, I pulled the spare IDM out of the toolbox and swapped them out. Truck ran like a top and like it should for the rest of that day and part of the next morning. Figured I'd found the issue. That was until I stopped for a bit bout 100 miles from home. When I left, it was down doing the same thing again. Wouldn't gain over 70 ish mph, egts were level.

Before I left for the trip, I changed all fuel filters. Oil and filter were new. The fuel that I ran on the 1st leg of the trip was the same fuel that I started experiencing issues with on the way home. Kinda perplexed since it mimics the MAP sensor issue from a couple of years ago that I had and similar IDM issues I've read bout others having. It's clearly a fuel delivery issue as the egts are lower and levelled when the power levels too. It's not consistent as this is the 1st time its happened in all the miles I've put on the truck pulling the trailer (18k) since October with trailer in tow. But then did it twice in 2 days.

Also, no codes. Fuel pressure is rock solid.

Ideas, thoughts, suggestions?
 

Charles

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So not sure whatever up with my 97. Just got back from a 1400 mile trip pulling the horse trailer. Truck ran great for the most part till the way home. Would get up to speed, 60 ish mph just fine then just seemed to level off on power. Egts would not climb over 1050 to 1100 and couldn't get any speed over 70. It was running like a bone stock 90cc injectored obs with no chip. Except have the mods in my sig and with this setup and stock programming, it runs like a chipped stage 1 injectored rig. Pulls hard, has plenty of ripened normally and will easily push past 1200 egts when pulling (although that's my personal limit to start backing out of it). Tried shutting the truck off, restarting, nothing changed.

I remembered a couple of years ago that I had a similar problem and it ended up being a had MAP sensor. Last year when I redid things under the hood I replaced every sensor, including the map, with a brand new one. Still I checked to see if that was the culprit and unplugged it. Still no change now, whereas that helped me diagnose the similar issue a couple of years ago.

So when I stopped down the road a ways for fuel, I pulled the spare IDM out of the toolbox and swapped them out. Truck ran like a top and like it should for the rest of that day and part of the next morning. Figured I'd found the issue. That was until I stopped for a bit bout 100 miles from home. When I left, it was down doing the same thing again. Wouldn't gain over 70 ish mph, egts were level.

Before I left for the trip, I changed all fuel filters. Oil and filter were new. The fuel that I ran on the 1st leg of the trip was the same fuel that I started experiencing issues with on the way home. Kinda perplexed since it mimics the MAP sensor issue from a couple of years ago that I had and similar IDM issues I've read bout others having. It's clearly a fuel delivery issue as the egts are lower and levelled when the power levels too. It's not consistent as this is the 1st time its happened in all the miles I've put on the truck pulling the trailer (18k) since October with trailer in tow. But then did it twice in 2 days.

Also, no codes. Fuel pressure is rock solid.

Ideas, thoughts, suggestions?



Verify that you're actually getting Accelerator pedal voltage increasing as you push your foot beyond the point where it stops pulling.

Then I'd unplug the ICP sensor to see if it took off, meaning the ICP sensor was screwed, making the PCM pull back duty cycle, keeping ICP low.

Does it stay crispy, or soften down when it lays over? If it gets soft and quiet then it could be ICP.
 

Strokersace

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Didn't see this till now Charles. How's the best way to test the voltage at the pedal? Never had to do this before. Also, will try unplugging the icp tonight.

I've noticed that driving it empty this week, it seems softer even at lower rpm and speeds. Not just on the top end. But up high is where I notice it more.
 

Strokersace

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Unplugged the ICP on Sat when I had to pull the trailer. No change is power. Still "dull" and experiencing the same issues as before.

Will an Aeroforce scanguage check accelerator voltage? That's all I have right now. If not, then I need to see if I can book up with somebody with an AE.
 

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