300Tdi rough idle

chris snell

Administrator
Callsign: NW5W
Staff member
I just got home from a long trip out west in my 300Tdi-powered truck. Right before I left, I changed the oil and adjusted the valves and it seemed to be running well. About halfway through the trip, I replaced a failing water pump (bad bearing) and the engine ran very smoothly after that. As I drove back to Kansas, the motor got rougher and louder and sounds quite bad now that it's back home with ~3500 new miles.

Obviously, it's due for an oil change but I think something else is going on. I have some ideas for diagnosing but want to run these by some of the more experienced deisel folk here. Here's what I think I should do:

- Change oil
- Adjust valves and possibly inspect the little caps and the adjustment locking nuts
- Drain sedimenter and replace fuel filter
- Go through timing belt replacement procedure, replacing pulley and tensioner and belt and re-time the motor. Motor only has 24k miles on the clock but if I'm going to go through the hassle I might as well do the belt.
- Test injectors (no idea how to do this)
- Test compression (no idea how to do this)

Thoughts?
 

Napalm00

Technical Excellence Contributor
What type of noise ?
Does it follow engine rpm ?
Is it present in neutral and or with the clutch pedal pushed in?
Is it present with the tcase in neutral?
Is it present when not moving ?
Check for boost leaks and blocked intake/filter


These can narrow down if it is In the trans, tcase or clutch mech.

Then check the valves, keepers and lash caps. To check the lash caps you need to loosten the valve adjuster completely and.use a magnet. Inspect for flaking chrome and amushroom shape. If they are bad replace and readjust lash.

Since it's a 300 also check the vac pump as they fail kinda often.

Then if it still isn't found I'd check timing with a gauge. This does not require the belt to be changed or touched

Testing the injectors requires they be sent out, since the 300 injectors are single stage any Bosch diesel shop can test them.

Testing compression requires a diesel compression tester there is a shitty one available at hf.
 

chris snell

Administrator
Callsign: NW5W
Staff member
It's not a single noise, just rough running, as if the engine is unbalanced. My suspicion is injectors or timing but just not sure at this point.
 

chris snell

Administrator
Callsign: NW5W
Staff member
Do you have any good videos that you like for verifying timing with a gauge? The procedure that I'm familiar with is pulling the front cover, putting the pin in the IP, putting the pin in the flywheel to ensure TDC, and checking the arrows/marks on the pulleys under the front cover. I have only done this a couple of times (during the install of the motor) and I'm super rusty. I'm not sure what kind of gauge I'd use.


The motor seems to have all/most of it's power, it's just very shaky and louder than normal. I'd be shocked if this was a fuel system issue that wasn't the injectors or IP. My hunch is that one cylinder isn't firing with proper fuel or with the right timing.
 

RBBailey

NAS-ROW Addict
Callsign: KF7KFZ
When I have described my rough running, and in ticking off the boxes in my head, I kept coming back to something to do with fueling as well. In my logic, it seemed like the one place where I could get different results on any given day, as I seemed to be getting. I think my roughness has settled down since I replaced that one injector. At least, I drove it for a week, and I don't remember ever obsessing over it, it never caught my attention like it had been. I also think my truck likes B20 better than straight diesel.

So I'd look at the valve clearances, but I'd also look to the fuel pump, bad fuel from some odd joint along the trip, or something to do with one injector popping off out of time or...

...but you've read my posts, and know that I'm an idiot, so this probably means you should look at something completely different! LOL!
 

Napalm00

Technical Excellence Contributor
May be bad fuel as well. I have some intermittent rough idling due to what i think is poorly tuned injectors.
 

Dan kemper

Founding Member
Callsign: KK6ECF
Chris just send your injectors off to be tested by blue ridge and or any other reputable diesel outfit
 

chris snell

Administrator
Callsign: NW5W
Staff member
There is a Bosch-certified diesel shop down the road in Salina. I think I'm going to pull them and run them out there.
 

broncoduecer

Technical Excellence Contributor
I'm guessing not; but would there be enough of a heat difference in the cylinders that you could pick them up with a infrared thermometer?
 

1of40

Well-known member
Chris, while the injectors are out being tested, if you are bored you can pull your fuel stop solenoid to check for metal shavings. You may know our fuel is not as our IP’s were designed to run on these days. As a result the cam starts to cannibalize. If you find specs down inside then your IP is on its way out and may be a reason for bad performance.
 

copleymotorcars

Well-known member
if it is simply rough idle, verify that the idle speed stop is adjusted properly. if it backed off for any reasons and it is trying to idle too low, it will nearly shake itself out of the car. this has happened several times with my 200tdi.

adam
 

RBBailey

NAS-ROW Addict
Callsign: KF7KFZ
if it is simply rough idle, verify that the idle speed stop is adjusted properly. if it backed off for any reasons and it is trying to idle too low, it will nearly shake itself out of the car. this has happened several times with my 200tdi.

adam

Is this one of the screws on the back of the pump?
 

chris snell

Administrator
Callsign: NW5W
Staff member
I've already bumped up the idle and it didn't help. It's a really rough idle. I've always run Stanadyne in my fuel so I'm not sure if it's an IP or motor lubrication issue but I will check the solenoid just to be sure.
 

gustavoullmann

New member
Hi, Chris

If you have recently adjusted the valves, what may have happened is the bolt that fixes the shaft of the rocker arms on the head lost the thread.

Sorry for my english, I speak from Brazil.

Enviado de meu Moto G (4) usando o Tapatalk
 

AdamSanta85

Well-known member
I've already bumped up the idle and it didn't help. It's a really rough idle. I've always run Stanadyne in my fuel so I'm not sure if it's an IP or motor lubrication issue but I will check the solenoid just to be sure.

I would guess an injector problem. You would probably have poor braking if it was your vacuum pump. If a rocker was loose you could hear it like a tapping sound. If your fuel injection pump was bad, you probably would have had/have other symptoms before this such as stop solenoid sticking (truck won't turn off) or smoking or poor performance.

Any chance you can post a video?
 

jymmiejamz

Founding Member
Callsign: KN4JHI
I rode with Chris a couple days ago. It is definitely rough, but overall sounds pretty normal.
 

chris snell

Administrator
Callsign: NW5W
Staff member
So I did a valve adjustment and surprisingly, several were quite out of adjustment. Makes me wonder if I switched up the feelers accidentally but I don't think I did. After a fresh oil change, it's back to its usual pre-trip level of roughness but stil soooo much noisier than Ben Little's 200Tdi.

My braking has been shitty lately so I'm going to swap the vacuum pump and see if that improves anything. Still thinking about running the injectors over to be checked, for the hell of it.
 
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