Good Evening TBI people that knows more than me...

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Bergenser1

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I am at an absolute loss with my truck, maybe somebody here has an idea....
It has a new GM Goodwrench Performance crate engine (JEG'S part number 809-12681430), was installed summer 2018, and has less than 3k miles. Transmission was rebuilt earlier this year, less than 300 miles, and a JET Performance ECU was installed. I have flipped ECU,s, with no different outcome. I have had nothing but trouble with it lately, it idles fine, but as soon as it has a load, it sputters and backfires. I have tried 2 different distributors, replaced TPS and all temp sensors, runs fine on idle, and at all rpm's, when no load, but cant handle a load. If I floor it, it runs right up on rpm, and runs fine, but regular driving is no good. Anybody have any idea?
 

NightRunner

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I always say this because it was a miracle fix for my truck. I had the same issue with my truck, exactly the same. Replaced the inline fuel filter underneath the truck and the issue disappeared. Ran like a brand new truck.
 

Schurkey

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I have flipped ECU,s, with no different outcome. I have had nothing but trouble with it lately, it idles fine, but as soon as it has a load, it sputters and backfires. I have tried 2 different distributors, replaced TPS and all temp sensors, runs fine on idle, and at all rpm's, when no load, but cant handle a load. If I floor it, it runs right up on rpm, and runs fine, but regular driving is no good. Anybody have any idea?
1. What is the fuel pressure under load?

2. What, if any, codes are stored?

3. What does the data stream say--what is the coolant temperature, short- and long-term fuel trim, O2 voltage, O2 crosscounts, TPS voltage, etc?
 

L31MaxExpress

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Fuel pressure or 02 sensor is my educated guess but realistically it could be just about anything. Without seeing data from the datastream it is hard to say what for sure.
 

95C1500

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Pull the vac line off the egr valve. Plug the line and cap the nub on the valve. Test that out. Mine would stumble really bad accelerating from a stop. Did that and it stopped. Replaced with a new valve.

Still wasn't running right, checked fuel pressure and it was low (~6psi key on engine off, 9psi while running). New pump and it runs like a brand new truck. I ended up throwing just about every sensor at it because A) I thought it would fix it or B) I broke it while testing/removal... don't be like me! In the end, the EGR valve and the fuel pump were both bad.
 

98 Nitro

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When my 94 ran like crap under load I changed to an AcDelco cap/filter on the parts store dizzy and it started running great. You said you tried 2 different distributors are they AcDelco/Delphi ones?
 

D_Stacy

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I am at an absolute loss with my truck, maybe somebody here has an idea....
It has a new GM Goodwrench Performance crate engine (JEG'S part number 809-12681430), was installed summer 2018, and has less than 3k miles. Transmission was rebuilt earlier this year, less than 300 miles, and a JET Performance ECU was installed. I have flipped ECU,s, with no different outcome. I have had nothing but trouble with it lately, it idles fine, but as soon as it has a load, it sputters and backfires. I have tried 2 different distributors, replaced TPS and all temp sensors, runs fine on idle, and at all rpm's, when no load, but cant handle a load. If I floor it, it runs right up on rpm, and runs fine, but regular driving is no good. Anybody have any idea?

My 1993 k1500 blazer exhibits exactly the same behavior. After replacing all the parts you mentioned I finally changed the fuel filter and that helped but did not completely fix it.

I took mine to a shop and said “ fix it”. I’ll have it back within the first week of September. I’ll let you know what was wrong with it.
 
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