Engine/Transmission (1994 - 1998) High RPM missfire

[Chris Bultman]

I am having an issue with a bad miss/flutter at high RPM, 2800 and above. It hits about 2800 and starts to miss and smoke white, it will continue to rev until about 3200 and that is all the higher it will go. Does anybody have any ideas?



Thanks, Chris

 

[Centeno1]

me too

mine started when i had a 4gsk put in hasnt gone away but it stops me from revving above 3 grand

 

[Matthug]

It's called valve float! STOP DOING IT NOW! You'll need 60# valve springs to rev past 3000 RPM, your's happens to only like 2800 everyone just says 3000 because it's an average.

 

[Bob4x4]

Check your fuel pressure while driving under load... ... ... ...



Bob

 

[Forrest Nearing]

check your timing...



I seriously doubt it's valve float unless you've got like a million miles on it... my 97 would rev clean over 3500 w/ the stock valve springs at 230k miles.

 

[Matthug]

Mine floats at 3000 RPM, I set my governer springs to 2800 RPM so I wouldn't float them again.

 

[JoshPeters]

Sounds like timing to me. Get it down around 12 degrees it will devolp a hic-up 10 will give a bit of a miss, below that and I'm sure it's what your dealing with.



If your floating valves at 3,000 I'd stop driving that truck. You have a valve spring that's getting ready to break, or has broken.



Josh

 

[Forrest Nearing]

Mine floats at 3000 RPM, I set my governer springs to 2800 RPM so I wouldn't float them again.

how do you know it's valve float? what is your pump timing set at?

 

[Piers]

Valve float won't produce white smoke, but timing will. Here's a quick test, take the motor up to 3000-3200 but giving it only enough fuel to get there, miss propably won't be there, then take it up to 3000-3200 under full fuel, if it's starts missing and coughing up white smoke, bump your timing up. 16 degrees is a good alround setting

 

[Forrest Nearing]

I figured it would be the same on a diesel as it was on a gasser, but I haven't ever run into it...



valve float doesn't feel like missing/sputtering, just feels like you hit the rev limiter (unless of course pistons meet valves, then it feels like money escaping from your wallet!)

 

[Red Stroke]

Piers is right, Bumping the timing to 16 deg fixed that problem on one of my trucks.

 

[Chris Bultman]

Thanks for the help guys. I did like Piers said and slowly revved it up and even under very light throttle it still smokes and misses although the miss is not nearly as noticable. I am going to start by setting the timing to 16* and if that does not help I will install the heavier valve springs.

Does anyone in the Grand Rapids MI area have the tools to set the timing that would be willing to help with it sometime?



Thanks, Chris

 

[bluthndr]

I have Piers' 60# springs and mine does it at about 3500... Pump was set up to go to 4500, but I may have a fuel supply issue - haven't checked yet.