LLY intermittent miss

[briane]

I have an intermittent miss in my 2005 LLY. It is worst at light acceleration or steady throttle. If I accelerate hard it runs as it should. The miss feels the same as a gasoline engine would with a bad plug wire or spark plug. I have changed fuel filters twice, many tanks of fuel from different stations, Diesel 911 in the red jug added, all with no change. No check engine light or DTC's. 105,000 miles, no change in driving conditions or habits. I would appreciate any help prior to going to a dealer and paying mega-bucks for poor results. Thamks.

[More Power]

An educated guess would include a faulty injector (electrical) or FICM (control module that drives the injectors), as well as the related wiring and electrical connectors. I'd give the wiring a visual first. FICM wiring has caused some of these sorts of problems in the past.
By the way - welcome to the board!
Jim

[DmaxMaverick]

There is a recall/TSB for a similar condition, and applies only to LLY engines (2004-2005, not 2006). The injector harnesses at cylinders #2 and #7 chafe, and cause a miss. Eventually, the condition worsens until DTC's occur and limp mode (or entire bank shut-off) becomes frequent. The dealership may cover this, even with the miles/time you have on it (although, common sense escapes most dealerships of late).

[carco]

What DmaxM said.

[briane]

I had the engine running and started wiggling connections and wires trying to make it miss and no luck. I squeezed all the connectors I could to make things tight and no changes, could not make it miss. Gave up and started heading to the dealer. On the way I had no problems. Put about 80 miles on since and had a little miss once. I will take connectors apart and check for loos wires or corrosion. Hopefully I can get this one fixed. Thanks for the help.

[carco]

Based on what you just tried I would chk about warranty on the 2-7 inj wire repair.
I had it done and a slight miss came back, I wiggled like you described and it went away and came back in a few days. I then elec greased the 2, 5, 7 connectors and pulled the harness as much as reasonable to achieve some slack, all has been ok for 8-9 months.

[Rene O]

i read most of the replies quick question? code indicates loose wire or broken wire injector 2 and or 7. if wire is broke motor won't come out of it? mine can come out of it. like more info on recall of harness. all sugfgestions appreciated thanks.

[samjellison]

I had the exact same issue 3 months ago. When I had my truck smogged for reg. renewal at Sierra Diesel Injection in Dec I asked about the issue. Their first inquiry was, "did I use an additive?" I said yes, except for the last 8 or 10 fills because I ran out. After a few more Q&A they suggested I add some conditioner/additive. So I bought 2 12oz bottles of Red Line 85 Plus (what I normally use).
It DID clear up and quit "missing" on third tank. I since ordered another case and add 4-8 oz each fill (10 gallons, 'cuz I run on top half of my tank). Recently had a SE light come on. Code said miss fire on #2 injector. Now trying to clean it up with CRC Diesel Fuel Therapy.
I am a believer of Red Line 85 Plus ... been using it for 3 years. 107,000 miles. NO real issues. The "miss" was the first minor issue since I bought the truck in Dec 2005 w/ 48,000 miles.
So that's "MY" story ... an '04 GMC crewcab LLY:cool: