High RPM Shudder and injector testing

[lowpass7.3]

I have a shudder when accelerating hard above 2600 rpm. below 2600, the engine run smoothly. the shudder is there, but much less noticeable at high engine speed and low load. It starts great in all weather, runs with decent power overall, not crazy powerful though. It happens at the same rpm, regardless of which gear I'm in. I get ~13 mpg around town, and 15-17mpg on the highway.

I was thinking that it was most likely a bad injector. I'm mainly worried that I'm going to burn a piston when I take my truck camper on longer trips through the mountains.

I am going to pull the injectors and pop test them. Is it possible to have an injector pop at a pressure within spec and not leak, but flow too much or too little fuel? When people match injectors, are they just matching pop pressure and assume flow rate is the same for a given injector code?

Are there any other things to chase down to fix a high rpm shudder like this?

My truck is a '93 F250 4wd, factory turbo 7.3, 5 speed, 200k miles, 4.10 gears. The previous owner said the engine was rebuilt or replaced (he wasn't sure, the 1st owner did that work, i know both owners, but haven't been able to get more info on this) about 20k miles ago, so the fuel system could be stock with 200k miles on it, reman or new with 20k miles. I'm guessing original based on looks. The turbo needs to be rebuilt soon. The compressor wheel shows some erosion on the vane corners and there is some radial play. I don't have a boost gage or EGT installed yet, but am planning on it soon.

Thanks,
Mike

 

[IDIDieselJohn]

BY shutter do you mean the engine starts running bad and shaking? Cause my van is doing the same at about the same RPM's.

I think mine is timing related, just put in 8 new (rebuilt) injectors on it, and other than running smoother and having abit more pep, it's the same.


Smokes at idle, and pours out blue smoke when you get on it... (fuel smell).

 

[lowpass7.3]

It starts to run like a gasoline engine with a bad plug wire. Its not violently shaking, just missing a bit. It is a sharp transition though. it pulls very smoothly and starts to shudder right at 2600 all the way to the rev limiter.

I haven't checked or set the timing on mine. I have a pulse timing meter, but i need to fix a problem with the crank pickup.

 

[Agnem]

If one of my trucks had that problem I'd never know it! I seldom get my RPM's up that high. At those speeds, you could be talking IP or injector, but I'd get all your injectors pop tested as a starting point.

 

[chvycmnslvr68]

If one of my trucks had that problem I'd never know it! I seldom get my RPM's up that high. At those speeds, you could be talking IP or injector, but I'd get all your injectors pop tested as a starting point.

I agree I wouldnt want to run mine that high either ... diesels are built to pull at a lower RPM than gassers but you could be having an issue with either timing or fuel supply .. either one would do that do you have a suupply pressure gauge on it.. if not i would put one on .. it can be very helpful when trouble shooting small problems ... put it on after the filter

 

[lowpass7.3]

So 2600 rpm is excessive? The hp peak is listed at 3000 rpm. I don't rev it out that far all the time, but when i need to merge into traffic or just feel like getting on it, it seems like revving above 2600 up to about 3000 shouldn't be that big of a deal. There are some big jumps between gears. My truck kicks out a significant amount of black smoke under 1800 if i give it much pedal, which may be due to the worn turbo so i don't get much useable down low unless i want to dump loads of smoke.

for the fuel pressure gage, do you run a line so you can get the gage where you can read it while driving?

 

[itsacrazyasian]

Wow, i feel like a dirt bag since i rev mine out till it hits the governer and won't rev any more then i grab another gear and do the same.

 

[lowpass7.3]

So 2600 rpm is excessive? The hp peak is listed at 3000 rpm. I don't rev it out that far all the time, but when i need to merge into traffic or just feel like getting on it, it seems like revving above 2600 up to about 3000 shouldn't be that big of a deal. There are some big jumps between gears. My truck kicks out a significant amount of black smoke under 1800 if i give it much pedal, which may be due to the worn turbo so i don't get much useable down low unless i want to dump loads of smoke.

for the fuel pressure gage, do you run a line so you can get the gage where you can read it while driving?

 

[racer30]

Well I will be pissed if my engine won't rev past 3400, I need mine to cruise at 3000-3200 or so to make 65mph in the MH.

 

[6.9man]

nothing wrong with 2600 or 3000 they were made to run there if there weren't they would of stuck a different gears in them. mine when i had the 4 speed in it ran 2600 at 65 mph going down the highway

 

[Agnem]

This is true, you can certainly operate the engine anywhere in the RPM band. But know that the torque curve peaks around 1800, and anything after that is just throwing fuel at low gears. Yes, you may need RPM's to make good boost, or make that hill, but on flat and level ground, you really don't want to be turning over 2K if you want any fuel economy.

 

[6.9man]

This is true, you can certainly operate the engine anywhere in the RPM band. But know that the torque curve peaks around 1800, and anything after that is just throwing fuel at low gears. Yes, you may need RPM's to make good boost, or make that hill, but on flat and level ground, you really don't want to be turning over 2K if you want any fuel economy.

agreed

 

[racer30]

I will be running the 5.13 rear gears in the MH untill I determin if the engine will pull a taller gear. then I will replace the gears or add a brownie box. I hope you figure out this problem soon so I can add the fix to my list of things to watch out for.

 

[lowpass7.3]

With a 4.14 first and 2.37 second, if you shift at 1900 rpm, you'll start out in second around 1100 rpm. If i did that when I needed to catch up to traffic, I'd be blowing a ton of smoke and still not accelerating hard enough to be all that safe. I do shift around 2000 rpm when I'm just puttering around town when I don't need to keep up with anyone. I agree its way better for mileage.

Maybe my turbo being worn is really slowing things down that much, but I wouldn't expect the turbo to help much under 1500 rpm, even if it was brand new.