ok, I've hung around for a while here, not posting much of course but appreciate all the great advice I've found over the years.

Here's the situation: truck has been very hard starting (when it starts). if you get it running and are cruising along in OD at low RPM and ease into the gas to maintain speed for a hill or whatever reason it sputters a little, feels like the trans is hunting (it's not) and if you're not VERY careful it will just flat die and leave you stranded. I've done many many things to try and resolve this and am at my wits end here. things that have been done so far: 1. Plugs (4000 mi ago) 2. COPS (2wks ago) 3. Fuel Filter (was about clogged on last change a month ago) 4. Fuel Pump assy (it was putting out low pressure - done same time as filter) 5. FPDM (yesterday) 6. TPS (and thorough cleaning of TB - about 2mos ago). 7. MAF has also been thoroughly cleaned (same time as TPS and TB service). About 2yrs ago I had the full timing set, phasers/adjusters/guides/chains/etc along with the heavy duty oil pump installed. motor itself runs great, fairly quiet and strong (when it is running).

to me, this ~feels~ electrically related to fuel delivery, like fuel delivery is being interrupted. if I throw starting fluid in the intake it will fire and run (briefly of course) consistently. I love this truck and I want to hold on to it as it is now becoming more single purpose now that I've left the Chicago and live in rural AL now. I don't need it for snow and cold weather, it mostly gets used to haul a small single 3500# axle trailer for my mower, home projects, moving my kids back and forth to college, etc. probably down to ~3000 miles per year now. It has some miles, about 206k, at this point.

only code I see on the scanner is the occasional Lean Condition bank 1/2, given the age/mileage of the truck I assume this to likely be O2 sensors.

I've hit the end now and need some help, what ya got??

 

No. The sensors are doing their job and reporting a lean condition.

2005 had a bad batch of injectors, but they would generally stick open and leak. Not to say that they aren't dirty and plugged. The MAF may be clean, but it could be damaged. Neighbor has a 2010 CVPI that would start, run for a few seconds, then die. Only codes were lean codes. Turned out to be the MAF, unplug it and it would keep running. Replaced it and it runs fine.

 

dump a couple bottles of chevron techron in the gas tank while you are thinking about it.

 

so you think the o2's are probably fine, is that what I'm hearing?? more likely the MAF. I need to replace the connector there, the locking tab on the connector is broken, tho it has been like that for a very long time without issue and appears to be staying in place just fine so far. not discounting that as a problem, just sayin

with regard to the stalling/hard starts and the manner in which this is acting it is unlikely this is injector related, I just dont see all 8 injectors failing simultaneously and at the same time not throwing a single misfire code. I honestly could see the fuel pressure regulator failing would have a more likely chance of causing that behavior. after the filter and pump were replaced the thing ran great

Next week I'm going to drop it at a mech I know here in town that is pretty good and we'll see what he says. of course i'll run this past him and get his thoughts on this as well.

 

Unplug the MAF and see how it runs. It won't run great, it will throw a code, but it won't stall and be hard to start. O2's are most likely FINE but if you want to spend the money, it won't hurt to replace the front ones. If they were bad, it would probably throw different codes, not P0171 and P0174. Note that those were the exact codes that the CVPI threw with the bad MAF.

 

interesting on the codes, of course those are the same codes i was getting. I'll check into that a bit, see if I can get one at the local parts store

 

FIRST - unplug the MAF and see what it does, that costs nothing. If no improvement, then it's something else.

 

was going to try that, started it up and while it was idling down from a cold start idle and I was opening up the hood motor just died very suddenly, couldn't get it to restart though it would fire for a second once in a while while trying. so I wasn't able to try unplugging the MAF effectively yet.

 

Unplug it and try to start it.............

 

i did, no luck. spray starting fluid in and it fires. I feel like I need to check fuel pressure but dont have to tools to do so.

 

There's no test port. You need a scanner that can read the fuel pressure PID.

 

exactly, I dont have the tools for that. so it's off to the shop to see what's up at this point. gotta put it on the trailer next week and take it in.

 

still waiting to hear back from shop (I know he's busy) luckily I have a backup vehicle for now.

 

diagnosis arrived finally.

after a couple weeks at the shop they finally traced down the wiring harness to a loose connector in one of the ECU plugs. when it was running they could go in a wiggle the harness and it would kill the truck. they pulled the offending wire, found that it was arcing slightly and it would die. the said there appeared to be some water had somehow gotten in there and corroded the connector. he replaced the bad connector, dielectric grease to help prevent corrosion to other connectors and now the truck runs like a top even when you wiggle the harness plugs.

weird one for sure.

 

That mechanic sounds like a keeper!