rough idle on truck
Asked by GuruV3M2W Sep 21, 2018 at 09:25 PM about the 1996 Chevrolet C/K 1500 Silverado Extended Cab 4WD
Question type: Maintenance & Repair
i got a 1996 silverado 5.7 vortec that has a rough idle.It feels like a misfire
but no check engine light on.I have changed spark plugs wires cap and rotor
and it still does it.I put a new fuel injection unit on it last yr that was an
update to the poppet injectors.The ones that are like multipoint injection.i
need to know where to start before i take it to my mechanic.I usually do all
my own work and a mechanic my last resort.
8 Answers
Check for vacuum leaks, spray around intake with carb cleaner or either. If that's not it perform a compression or cylinder leak down test. Some parts stores lend tools like a compression gauge
ok i will try that next week when im off.This truck originally came with a 305 in it but i found a 350 and had a mechanic put it in awhile back but its kinda run like this since putting it in.The engine had supposedly been rebuilt and only have about 30000 miles on it but cant verify.I just did the intake gaskets about 2 months ago with no problems.
Stop. Wait did you change the Engine Contol Module when you changed the engine? It would make a BIG difference I hope this helps you
No but i do have the ecm for it that came from the other truck i parted out but it was a 2 wheel drive truck not a 4 wheel drive.i was told by my reputable mechanic that it would be fine going from a 305 to a 350.i couldnt use the 2 wheel drive wiring harness on a 4 wheel drive truck.
Will the 350 ecm plug in or does the four wheel drive ecm have more wires? There are a lot of parameters that are different between the two engine. Can you get an ecm for. 350 4+4 from a bone yard? I honestly think it would make a big difference
Dont know if it has more wires. I would think iy would be the same. The 350 came out of a 97 hmc 2 wheel drive but havent looked at the wire count yet but will.
I talked to my local dealer and they told me it didnt matter in 96 whether it was a 350,305 or 454. They all used the same computer. I had a friend check the truck with his computer and software like snapon has and the timing was out by a negative 13 degrees so it was out of time. Got it back in time and now runs great. The only problem now is a bad o2 sensor.
