Runs rough and wont idle

[rob5758]

My 94 "Problem Child" let me down.....again. Started running rough as if it was running out of fuel and then eventually died. I have fuel pressure at filter with it cranking,the lift pump is working like its supposed to. I cranked it till I almosted killed the batteries and then she started like it was ran out of fuel. Now, at idle it pings and runs rough, above 1500 rpms its fine,has plenty of power and smooth. If I let it idle it will eventually die and I play hell to get her started,and this didnt start gradually just all at once.
Any thoughts or suggestions before I cut her up in a million little pieces??:confused:

[grancito]

Any codes? Where is the pmd mounted?

[trukdoc]

...the fuel???how many miles on the b****???do you or have you run biofeul thru it??have you checked the frame areas for rust???my 94 came out of tenn. ran great for @6mths and then started the pmd/run out of fuel intermittant die...found fuel lines rusted with pinholes...replaced both inlet and return lines tank to ip and cured it,,,for awhile took an o-ring on fuel heater and finally walts pmd/heatsink to make it bullit proof...jd

[rob5758]

`Havent gotten any bio to her yet,PMD mounted on heat sink on firewall. Replaced fuel lines last year,new OPS and temp sender this year. Thinkin maybe injector??? How do they act when one goes out? Acts like a dead cylinder at idle then not noticeable at higher RPM's. But that dont explain the "running out of fuel" when she dies, and yet I have fuel at the filter......and when it runs, I have noticed a "whistle" noise and its not coming from any of the vacuum lines or waste gate.

[trukdoc]

...say it ,but it's probably time for a new injection pump...

[grancito]

If it is IP then there should be a code. Alternator will whistle if it is charging low batteries, mine whistles all of the time.

[rob5758]

Hmmm.... well I've been really short on time but will check the codes and get back to ya's. Come to think about it, I remember the light coming on then going back off so really didnt worry about it much. Will an IP go out that sudden?

[CAdiesel]

Every time the light comes on it stores a code, even if it turns off right away. So check 'em and let us know. Hopefully it's good news.

[trukdoc]

...mechanical injection part of that pump is going bad it won't always set a code...if it's mechanical and not a sensor in the pump...jd

[rob5758]

Ok I finally checked the codes,pull up a chair and grab a soda,its a long one.
36-injector pulse width error long response
35-injector pulse width error short response
62-turbo boost sensor
57-PCM 5 volt shorted
92-cyl balance fault (#2 cyl)
91- " " " (#1 cyl)
98- " " " (#8 cyl)
96- " " " (#6 cyl)
94- " " " (#4 cyl)
93- " " " (#3 cyl)

:confused: I'm thinkin maybe ECM????:confused:
It will start after cranking awhile, and after it runs it starts easier but not like it should. Above idle like around 1000 rpms it seems to run ok, anything below that it sounds as if shes only on bout half the cylinders.

[CAdiesel]

That's a lot of codes. I had all of them except the cylinder faults when my PMD went out. How old is it? Might be worth buying a cheap used one to test the theory.

[rob5758]

I have a spare, and swapped with my '97, no change. I even took the extension harness out of the picture.

[rob5758]

So we still thinkin it's the IP? Like I said, it happened all of a sudden without warning. And something else I'd like to know more about is the turbos on these things. The model is a GM-4, how many different models is there and how big of one can I put on?

[trukdoc]

...buy a pump,check the wiring harness under the intake...also the harness grounds at the back of the curb side head{2 wires}comm.mechanics don't always replace wire retainers,so you wind up with wires chaffing and wearing thru the insulation...since you pull intake to change pump check this while you're there...

[CAdiesel]

When you say you swapped the PMD and had no change I assume you mean the symptoms. Did you clear the codes and get all the same ones again? How old are each of the PMDs and are they the new thicker ones?
Like Trukdoc said rule out the cheap before throwing $$$$$ at the problem.
I had one PMD just quit, no codes (truck would die but restart), and one threw many of the same codes you have but the truck would keep running the same. Lesson is no two PMD failures are the same (great design).

[rob5758]

Well my '97 I drive every day and that`s the one I traded with,and it runs fine with that PMD. But I also have a new one that I bought for a spare some time ago, no change with that one either.
Here is another "thought" I`m gonna through at ya. I was told my 6.5 will run without a crank sensor. So could that thing flake out at low rpm`s and make it run like that, then come out of it at higher rpm`s?