The Diesel Stop banner

1 - 17 of 17 Posts

·
Registered
Joined
·
130 Posts
Discussion Starter #1
I bought a early 99 7.3 f250 a couple weeks ago and I replaced my injector o rings, glow plugs, and serpentine belt as it was squeaking. There is currently a 50hp custom tune from the past owner. I had my issue even before I replaced these rings. It's hard to explain and only noticeable when the truck is not moving, in park or gear. I do believe that I have a very small exhaust leak towards the back of the engine that must be on the very start of the downpipe.

Onto my issue: When I'm idling at a stand still, there is a vibration that I can hear and feel while I'm in the cab. It doesn't come in any certain pattern. Sounds like "smooth... vibrate vibrate... smooth... vibrate.. smooth smooth... vibrate..."(etc.) Since I'm new to my powerstroke, this could be completely normal, I have no clue. The actual idle of the truck stays undisturbed. I do notice a very slight jump in the RMP's when the vibration occurs. When I'm driving and I coast while barely pressing the accelerator the truck will vibrate as well, but it's consistent and only at a certain depression of the pedal. This vibration is not loud or anything but noticeable for me and my friend to hear/feel.

I can't find a past forum on anyone with this specific issue, but I've read that it could be bad motor mounts, the exhaust touching the tranny cross member bolt (I don't think this would cause a RMP jump), a bad serpentine belt tensioner or alternator.

Are there any other ideas? Like I said, maybe this is normal for the 7.3's. I can try removing my custom tune to see if that solves anything if I can figure out how. Thanks in advance for the help.
 

·
Premium Member
Joined
·
3,872 Posts
It could be two separate issues.
Do you have the A/C on?
Does it happen even when the HVAC is turned off?
Even the windshield defroster engages the compressor so the dial needs to be OFF to test.

The reason I ask is to eliminate the possibility its the A/C compressor cycling.
 

·
Registered
Joined
·
130 Posts
Discussion Starter #3
Yes it occurs with everything off. My ac compressor clutch won't even turn when I have the AC on so I figured I new a new compressor or a clutch plate. Secondly, I noticed it only vibrates when the truck is warm.
 

·
Registered
Joined
·
130 Posts
Discussion Starter #4
Update- my issue is still happening, I replaced the ICP sensor which seemed to be worn since it was stock and has oil in the connector, and it didn't fix anything with this issue. It seems to be vibrating more often since I made this form post so it may be getting worse. I don't think it's the engine mounts because the engine doesn't move at all when idling. It's not the program on the truck because it occurs in stock mode as well. I'm wondering if maybe it's the alternator or a pulley? I thought I read up on it causing an issue similar to mine but I'm not sure if that could cause a slight jump in RPM'S. Does anyone have any ideas? I would really appreciate it. Josh
 

·
Premium Member
Joined
·
3,872 Posts
Josh,
It could be a pulley bearing but it seems like you would hear that.

You should also be able to feel a bad pulley by removing the serpentine belt and spinning each one by hand.

The tensioner is often replaced at the same time as the serpentine but I think I replaced mine around 150K miles. They do wear out.

Do you monitor EOT? Are you sure its not your cooling fan? That makes a pretty loud noise but would vibrate and affect RPM.

You have already ruled out A/C clutch.
 

·
Registered
Joined
·
130 Posts
Discussion Starter #6
I don't think I can hear it when I'm outside of the truck. I'll take off my serpentine belt and feel the pulleys again and the fan for play. I don't monitor and temps yet but gauges are on my list.
 

·
Premium Member
Joined
·
3,872 Posts
Get yourself a ScanGauge-2 for $140 or one of the Apps that bluetooths i to your OBD-II.

Both cheaper than gauges.
 

·
Premium Member
Joined
·
469 Posts

·
Registered
Joined
·
130 Posts
Discussion Starter #9
Okay I'll get one of those, unfortunately I'll have to wait around 2 weeks until I get paid. I just cleaned my EBP tube and checked the pulleys, they all seem to be good, the only pulley that wouldn't spin easily was the power steering which I believe is not supposed to spin like the other pulleys in the first place. The PS pulley had a slight amount of play in an out (about 1mm). Thanks!!
 

·
Premium Member
Joined
·
3,872 Posts
The tensioner pulley felt smooth?

Since it might be getting worse, maybe it will become easier to diagnose.

Still thinking about how your old serpentine belt squeaked. I never had a serpentine squeak but did have pulley bearings that did. The old style individual v-belts used to squeak.
 

·
Registered
Joined
·
130 Posts
Discussion Starter #11
Yes it felt smooth to me, I might just ignore it for now as it's not a very loud vibration and doesn't bother me much, I just wanted to possibly solve it if I could. I'll check the EOT among other temps once I get that scanner. Thanks for the help ArcticDriver
 

·
Registered
Joined
·
130 Posts
Discussion Starter #12
Update- My problem persists but hasn't seemed to get any worse. AutoZone has a sale on the scangauge 2 for $110 right now so I could pick one up this coming Friday. Should I still plan on buying it?
 

·
Premium Member
Joined
·
3,872 Posts
I don’t know if it will help identify your issue but I think they are a good tool to have. I have one in each truck.

But I forget your model year. They may not be a big benefit in early 99 trucks and before.

There are also Bluetooth alternatives that guys are happy with but I will let them describe why they are good.
 

·
Registered
Joined
·
5,290 Posts
Let's talk vibration. Cylinder misfire or low cylinder contribution is a vibration at idle that you could count out loud like, "that, that, that, that", There is a resonance (fast vibration) from crank slowing on a compression stroke and crank acceleration from firing a cylinder. This lesser amplitude vibe is much faster, more like some electric vibrator they might use on muscles, etc. The resonance vibe is very sensitive to RPM and the PCM controlling idle speed and changing it 25 RPM might put it in and out of the sensible vibration range, especially if motor mounts are settled from aged rubber, exhaust is missing hangers or stressing hangers, and if it is a manual tras the wear of damping springs in clutch disc (you don't mention whether auto or manual trans).
If the vibe is occurring does it go away if you just barely raise engine speed by very light throttle pedal press?
SO what kind of vibration is it?
 

·
Registered
Joined
·
130 Posts
Discussion Starter #15
I checked the exhaust, it's not that, and it's an automatic. Yes, when I barely press the gas, it does away. It's a smooth sounding vibration, that is sporadic (random) and usually occured ever second or so but sometimes vibrates right after another vibration. The vibration usually lasts a half second to 1.5 seconds approximately. It doesn't seem to vibrate when the engine is cold. It does almost sound like someone is putting one of those sports vibrators on my frame to the point where I can barely feel it and hear it. It's definitely not harsh or theatening sounding. I hope this helps 😕 thanks!
 

·
Super Moderator
Joined
·
25,012 Posts
Have you checked the transmission fluid level? Does it do it in gear or out of gear? If only in gear, it might be a torque converter issue or fluid level thing. I'm no auto tranny expert but it's at leas worth checking the fluid level.
The early '99's had torque converter issues, but I would think that would have reared its head long ago.
 

·
Registered
Joined
·
130 Posts
Discussion Starter #17
Yes I checked the fluid when I got it and it was good. I'll check it again soon. It only happens out of gear when I'm in park. When I'm driving though and I depress the gas about 20% (only while coasting) the truck will vibrate way worse then when in park and it's a constant vibration instead.
 
1 - 17 of 17 Posts
Top