[GKPrice]

Hey guys,
A friend called me this morning to help with his truck. He was a few blocks from home ending a faultless 100 mile trip when the truck started to cut out. He limped home with cutting out, surging and combustion rattle. I joined in at his house and after checking codes (no codes) we cranked the truck. It idled very rough, seeming to surge at about 1000 rpm. Within about a minute it settled down and developed a smooth idle a little under 700 rpm. We closed the hood and started down the road and it began bucking, cutting out and running roughly though still pulling strongly. We put in some fuel (it was low) then had fuel filters changed, then had codes checked at Oreilly, still clear. Neither my reader or the one from Oreilly can monitor operating parameters, so all I know is the behavior of the truck.
The truck very much acts like it has some air trapped in the fuel system, which should clear out in time (Like it seemed to earlier.) We pulled the secondary fuel filter and turned on the key, got immediate clear fuel w/o bubbles. Fuel comes clearly but I can't estimate if there is sufficient flow.
Here's the part that is a bit of a stumper. In city driving, the truck idles somewhat high and wants to GO, even as it is cutting out, but if you can go WOT for a few seconds (say 20 mph to 50 mph) all foolishness stops, she digs in and once you get boost, you're gone. If any of this involved fuel starvation a hard throttle excursion should magnify the issue I would think.
I'm actually leaving town on Sunday and the truck is going to the dealer Tuesday unless we get some resolution here.

What say you?
And Thanks!

 

[bismic]

Where is the location of the ICP sensor? This determines if it is an early or late 04.

Have you tried disconnecting the ICP sensor and running it on the "inferred" value? This might help, but be aware that running it disconnected WILL through a code.

If it is a late 04, then you might also try running it with the EBP sensor disconnected.

Without a good scan tool of your own (ie ForScan downloaded to a smartphone for $6, and a $35 OBDII adapter), that is about all that we can do.

 

[6LiterTeter]

Where is the location of the ICP sensor? This determines if it is an early or late 04.

Have you tried disconnecting the ICP sensor and running it on the "inferred" value? This might help, but be aware that running it disconnected WILL through a code.

If it is a late 04, then you might try running it with the EBP sensor disconnected.

Without a good scan tool of your own (ie ForScan downloaded to a smartphone for $6, and a $35 OBDII adapter), that is about all that we can do.

Interesting… run it with EBP disconnected? Do tell. Or, reply to my awesome latest thread 😉.

 

[GKPrice]

Bismic, You have my undying gratitude sir!
It is an early 04, IPC sensor buried under turbo, burp tank, kitchen sink, etc, etc.....
Finally found the harness connector, got it off, started the truck and it idled like a dream, but did throw a code. My friend knows how to go forward from here. I don't understand how an sensor inputting data to an ECM can go anomalous enough to cause major issues without throwing a code, but hey, nobody ever accused me of being all that sharp.
Once again sir, I'm grateful for your help.
Good day!
GKPrice

 

[bismic]

Be sure to replace the sensor connector (pigtail) also. They get oil soaked from the failed sensor and degrade. It is probably the resulting bad connection that is the issue behind the erratic performance.