I happened to notice tonight with the predator , that this stumble I have had in my motor for a while, happens just about in a perfect cycle. Like every 20 seconds it's like a very light brake tap and then it goes back to normal. I was watching timing with cruise set at 45(where it is most noticible) the timing sits between 38-41 deg. and all of a sudden the timing falls to 15-18 deg. just for a split second and goes back to 38-41. it is like clockwork.
I have changed plugs, cleaned air filter, top end cleaner, fuel filter, checked for a vac. leak using brake cleaner, used high octane, checked fuel pre. regulator, checked electrical connecters, Anybody have any suggestions?

 

i just got a custom tune from johan at diablosport, i never noticed it before the tune, but if i am easy on the throttle, my truck almost acts like it stumbles before the 1-2 shift. the tune i got has been great so far but i never noticed this before. wot it goes no stumble so i wonder if it could be the same prob.
i have no idea of what it could be. hopefully someone can chime in and help us out. besides saying get rid of it.

 

I've had driveability complaints in the past that sound similar to yours that turned out to be the cycling of the A/C compressor. You might try your your 45 mph cruise with the A/C off and see if it's that.

 

oh yea, the a/c is the only thing that i can think of that might cause that. then again, i am no electrical expert so i am just guessing. was your a/c on? did the compressor kick on maybe?

 

damn he just said what i was thinking. good call

 

Is the overdrive on or off? and can you accelerate through it? if so it might be your plug wires. My Tahoe was misfiring and it was only noticable at low RPM's in overdrive because of the gearing, and engine load. Good Luck

 

I ran it with the a/c on so I'll try no a/c today and try and check out plug wires too. I've got a tune from Johan too and have tried with or without the tune same result.

 

I forund out the same thing last year. The Predator was good for something. Here is my thread about it.

https://ls1tech.com/forums/showthrea...ighlight=A%2FC

 

Pull your spark plug wires off and put an ohm meter on each one. They all should be a with in few ohms of one another. If one is more than about 80 ohms higher than the others than it is bad. There is are normally about 2-5 ohms difference between them. Mine was doing what you described and I had a bad plug wire.

 

Checked my plug wires came to anywhere between .41 to .44 kohms. What are they supposed to read? Have not gotten a chance to run the truck much today big I did notice some difference with the A/c off but I have not even drove it far enough to warm the engine up so I can't say for sure. Very interesting about the A/c timing deal. I going to have to check that out. Maybe I am just having normal stuff happening, but I bet mods just amplify the problem.