Hi all, once again I am turning to the gurus (and you are!) to help diagnose a problem I am having with the old girl. The facts: 1995 F250 xcab, 180k miles, 6637 intake, 4 inch lift otherwise stock longbox. Regular oil changes and filters, coolant additive, quality fuel, new lift pump about 12 mos. ago etc. At idle the thing sounds like it's coming apart. She's had this problem for probably 9 mos. although it is getting more and more prevalent Shakes and I wouldn't characterize it as stumbling, but definitely running rough. Rev it up and it smooths out. Sometimes if you just barely put your foot on it, and raise the RPM up to about 600 or 650, then take your foot off it, she'll smooth out and idle normally. Sometimes it will go back and idle rough again after a few seconds sometimes it stays idling normally. If I lug it a little bit in 4th or OD, it seems to run a little rough too. Found a burnt pin in one of the UVC harnesses but it was a glow plug pin, not an injector pin. Having done a little research on these pages, I have (I think) narrowed it down to one of several problems, although none of them encompass my exact symptoms. What I'm thinking-needs injectors/O-rings, air in HPOP not bleeding off, needs to have more fuel pressure (FPR shim), needs new UVC wiring harnesses. What think you fellas? I'll be checking back in on the site a couple times a day now that I've put this on here...so if there's more info needed, just ask. Thanks so much for your past and (I'm sure) future help. You all ROCK!!

 

have you had it scanned for codes yet?

 

If manual transmission; check for bad dual mass flywheel, this will cause false cylinder codes if the flywheel is bouncing around, especially at idle. Not that I know that much about dmf's, just what I read.

 

Don't have access to a scanner right now. What would indicate a "bad" dual mass flywheel ? I had a Luk clutch put in about 38k ago. Was alright to start with. Now it's a little jittery, esp. with a full load of wood on. Thanks for the posts. Any other ideas or things to check ?

 

How long since you cleaned the FPR screen ?...

 

Cleaned the FPR screen about a week ago. seemed to be more stuff than usual in the filter bowl than usual. I guess if the screen is plugged, it starves the motor for fuel. Is this right ? It's getting cold here and harder to start, probably due to a glow plug or two not working, and i'm thinking more seriously every day about getting out of the diesel business.

 

The screen is on the return ,,if it is plugged ,,the fuel system may have air trapped in it...

May cause an un even idle ...

Is it the same ,engine warm & cold ?...

 

As you have a Luk I would rule out the clutch. Recheck the FPR screen use a small mirror and flashlite on the inside of the fuel bowl with filter out....use Q-tips with diesel on it to clean. Shim the FPR. Check the nut (the tin nut) on the end of the HPOP injection pressure regulator. The IPR is found on the driver's side of the HPOP and has a wiring harness plugged into it. You will see a tin nut which sometimes comes loose, just be careful when tightening as it will bend easily. You also might want to tighten all the fuel line connections (rubber hoses) around the fuel bowl and fuel pump, do it when the engine is warm...and while you're at it check all the HPOP lines too...

Does it start right up when engine warm?

 

sounds like the IPR to me

 

Are you getting a check engine light at all?

Have you ever changed your Injector O rings?

When you changed your lift pump did you clean the bottom of your fuel filter housing ?

If so what did it look like?

what colour is the fuel in the filter housing?

 

Thanks for all the replies. If the IPR nut had come loose, would I have oil leaking out of the HPOP ? I will check it to be sure. I put new glow plugs in today, one burnt pin on the UVC wiring harness. It was a glow plug pin on the front passenger side connector. Replaced it. While in the glow plugs, I looked at all connections on the HPOP and fuel lines. I have nothing leaking, loose or disconnected with the exception of the fuel bowl heater. Action4478, the condition is the same cold, warm, or hot. I'm begining to think the fuel pressure may just be too low at idle. When you rev it up, it smooths out and runs OK. I think after the 2 year old goes to bed tonight, I'm going to check fuel pressure, clean the screen (again) and do the FPR mod with the 10 year olds BBs. LOL All connections related to the injectors, glow plugs seemed good, but took harnesses completely off and reconnected. Seems to run a little better now that I cleaned the screen and harness connections.
Jcart- Yes the engine fires right up if its even the slightest bit warm.
WalJon- No check engine light, that's one reason I haven't gotten serious about scanning it yet. I heard if it's throwing codes, the CEL will come on. The injectors have never been touched to my knowledge. I have an extra special request in with Santa on this. I replaced the lift pump with the filter housing in place, so I have never looked at the bottom of it. I did clean the valley of doom out really well with some simple green. It's gotten a little dirty again since, but nothing like it was when there was diesel leaking there. Fuel in the filter housing looks like regular diesel, a golden greenish color I have seen since I've been changing filters. One more detail of this minor glitch is the fact that if it sits idling for a minute or two, sometimes the idle corrects itself and will idle correctly for some time and then go back to idling crappy. It almost seems as if the computer reads the bad idle and corrects it but then will let it go back to shakin' and shudderin'. 'Course sometimes it just idles crappy the whole time it's idling. Sorry the long post, you all are real decent to read and post back. Thanks heaps!!

 

The nut on the IPR only holds the soloniod in place ,,take a look at it...If its loose , it could have those symptoms ...

Unplug the ICP connector , look for oil in the sender ,,then start it with it unplugged ,,see if the Idle smoothes out ,,,

 

what did we decide about the flywheel, does luk clutches convert to a single mass? and the idle on the ps's is never perfect, how rough does it get?

 

I though that it comes & goes ,,may not be the flywheel ...

 

Tried unplugging the ICP, idle unchanged, checked the IPR nut and connection, both look fine. Not a lot of fuel or dirt build up on them either. Put in the FPR shim mod and seems to run better. Went from 55# to 80# fuel pressure. Going to run that a week or so and see if it contunually gets better. Anyone got any ideas about how high fuel pressure it too high? I don't want to hurt more than I help. I was going to put in a IPR rebuild kit just to see if that's the answer, but man, that thing is wedged in there tight. It looks like a guy would have to pull the fuel bowl assy. to get to it. On top of making the wrench shown on the IPR page. Ideas still welcome tho. Thanks all!!!