96 k1500 intermittent rough idle

[chevyCowboy]

My 96 does this very randomly. Did it about 2 weeks ago and haven't had any issues since until today. Have a new pmd that has been relocated and the grounds are all good. Seems to me that it is more than likely something in the pump but thought I would see what the group thinks. Only has issues at idle once rpms are up every thing seems normal.

 

[chevyCowboy]

Computer wouldn't upland so tried to use phone says doesn't have allowed extension

 

[chevyCowboy]

im not sure why I cant upload the videos

 

[Jaryd]

You will have to upload it to YouTube and post the link here. You can’t upload videos straight to this site.

 

[ak diesel driver]

Sounds like air to me

 

[chevyCowboy]

You will have to upload it to YouTube and post the link here. You can’t upload videos straight to this site.

well I haven't been around In a while I thought we used to be able to ill give the youtube a go

 

[chevyCowboy]

here is the link 96 chevy 6.5td rough idle

 

[Will L.]

Lets see that clear line on the ip Return please.

There was that reflash thing that affects some rigs. They do great for years then goof. Reflash and poof. Not sure this is following that but figure I’ll throw it out there Incase you do all the normal stuff with no results.

 

[btfarm]

well I haven't been around In a while I thought we used to be able to ill give the youtube a go

Well that's what ya get for not hanging out here often enough...;-)

 

[chevyCowboy]

Well that's what ya get for not hanging out here often enough...;-)

Yeah I haven't had any truck problems to speak of and with two little kids and house projects I've been staying busy. the few small problems I have had I've learned enough over the years from here to be able to fix on my own

 

[chevyCowboy]

So who wants to save me the digging since I can't remember where the best place to put the clear line to check for air

 

[Will L.]

The front of the ip ia a 6” long piece of 1/4” id hose. Right behind the oil fill. Swap that and use new screw style hose clamps cuz the squeeze type doesn’t always hold the clear stuff.

Just put it on and leave it. It’ll need swapping out in a few years, but so cheap and easy it’s worth it for anytime& anywhere diagnostics.

 

[chevyCowboy]

That's what I was thinking was the spot but couldn't remember for sure

 

[ak diesel driver]

Don't even have clamps on mine

 

[Jaryd]

Don't even have clamps on mine

X2

 

[chevyCowboy]

All right fellas this truck didn't do this all winter long and now it started doing it again. I put the clear tube on and no air bubbles to be seen, seems to be something electronic because it's very intermittent one time you start the truck no troubles the next time runs like crap any more ideas

 

[chevyCowboy]

The other weird thing about it i
s that when you come to a stoplight it will stutter a couple times but as long as I hold my foot on the brake the Idle evens out.

Seems to have good lift pump pressure. I can open the water drain with truck running and it still runs.

Another odd thing is that at idle it's around 4 or 500 RPMs, seems a bit low to me

 

[Will L.]

Have you taken a fuel sample into clean glass jar and let it sit for inspection of contamination?

When you opened the drain checking pressure (via it flows out instead of sucking air method) — did it studder while you had valve open? No effect of flow during studder? If you are not 100% positive on this, do it again while checking for sample. You might need to fill a jerry can from the drain waiting for it to studder and see if there is any change in flow. Any change could be a pressure related issue.

Truly a pressure gauge is best to see. @WarWagon had the dreaded fuel line flapper right at the ip inlet that caused him tremendous hard to find issues. I have seen it multiple times over the years. That why I am so strong about a T in metal fittings right at the ip inlet. I’ll see if I can find pics he sent me incase he doesn’t post link to his here for you to see example. This can happen anywhere in the system, but th only place to read it is at the ip.

Remember, fuel pressure gauge on the dash will
Pay for itself when liftpump dies and you are wearing out the ip so much faster and dont know it. Don’t need fuel line in the cab- electric gauge and a sensor only at the ip- 1 wire to bring in the cab.

Another possibility is fuel you are buying. They changed to winter blend near you? If so and problem When away, then return as they go back?

Turning on A/C requires raise in rpm at idle for compressor load. Ds4 uses pcm to do this iirc. Db2 has a solenoid. Anyways- if you turn on the a/c toax recycle mode (fan speed doesn’t matter) it should hold rpm higher and steady. See if that affects it.