After basic tuneup still misfiring.

[1Kurgan1]

So the truck has been having some issues misfiring under moderate load the the beginning of the gears. I replaced the cap/rotor/plugs and it helped slightly. Next I plugged the egr line running to the TB (after the electrical part) and it seemed to run very good. So I picked up an EGR valve, pulled off the old one and it seemed to work fine, but I went ahead and just put on the new one. And since then it's running worse than ever, after it shifts to a new gear I have to baby it up in speed or it just falls on it's face misfiring. Before it would do that a bit around town, but wouldn't fall completely on it's face, and on the freeway I had 0 issues with it. Now it even has some issues there. Any ideas?

Also it is a 91 5.7L K2500.

 

[sewlow]

Try replacing the coil.

 

[sewlow]

Or... Replace the inline fuel filter, under the truck, along the frame rail.

 

[Vigh_J]

Or... Replace the inline fuel filter, under the truck, along the frame rail.

Mine was doing the same thing man...replaced fuel filter, all was good. Sounds like exact same symptoms.

 

[1Kurgan1]

Fuel filter was next inline to get replaced till it started misifiring worse after the EGR was replaced, that puzzled me. Guess I'll pick one up this week and hope it fixes it.

 

[93Chevy_1500]

I had the same problem with my 93 2wd that i had. It would misfire like crazy and have no power until i got it up to speed then it would cruise all day long until you slowed down and went to pick up speed again. It was weird. I changed the fuel filter, map sensor, tps, egr, complete tune up and didnt change a thing it was the weirdest thing i have ever encountered. I think it was in my injectors. But idk sold it while i was ahead.

 

[1Kurgan1]

Mines a bit more sproadic than that, yesterday had to take it for a 75 mile round trip to my parents, hit the freeway on the way there, after I got off the freeway it ran like a champ. And continued running great till I got home and hit the city street (stop and go driving). I got a new fuel filter, but the 5/8" nut wasn't budging, so I'm going to continue hitting it with WD40 for a few days and try again. The lines not corroded at all ,but I hope the nut turns off, and when it does I hope it slide around on the line, if it twists the line I'm going to be very sad.

 

[1Kurgan1]

Well just replaced the fuel filter and it helped a bit, but still there. So far I have done, Plugs, Cap, Rotor, EGR Valve, and Fuel Filter. Was talking with a friend and he maybe suggested the timing could be off. So I'm going to pick up a timing like and see, any other suggestions?

 

[MIHELA]

Was it an aftermarket EGR? I've heard that they all have the wrong springs in them and will cause problems.

 

[1Kurgan1]

It was, I kept the factory one and will give it a shot. But the misfiring has remained basically in the same manner (pattern) as it was before any maint at all. The only time it got worse was right after I put on the new EGR, but the next day it was back to being about the same, maybe slightly better than it was.