hesitation/backfire?

[willfull04]

I've got a new engine with 2000 miles, and it runs beautifully. There is a bit of a hard starting problem (similar to a hard starting that I had on the previous engine, and the oil-pressure switch fixed) I just haven’t found a socket that fits the oil-pressure switch to replace it and it happens rare enough I forget about it.

I am also experiencing hesitating when accelerating hard from the 50-60 mph range. Hesitating isn’t accurate, but I am not really sure how to describe it. It is like a series of “thuds”…not sound, but feeling like hitting randomly spaced potholes (but there aren’t any potholes). It only happens if im already at 50-60 mph. I have tried to replicate it in neutral at 0 mph and cant, and after it clears up it wont happen again until the engine has shutdown and cooled (I cant be more specific on how long it cooled for). The dealer who installed the engine did not have the tools to pop test my injectors, they only have 20k on them so I opted to keep them. He did however fail test them and said they all passed. I am wondering if this is related to the hard-starting? Do you have any insight? The engine currently has almost 2000 miles on it.

I am very happy with the engine and I consider these 2 problems very minor as long as they aren’t causing damage.

[Craig]

Did your mechanic, after installing new engine, use a Tech II to reset things like the timming?

[willfull04]

yes i did. i have a chip from another company controlling the timing, and the TDC offset is set to -1.94.

[oldtrucker]

Willfull, NAPA has socket make for OPS bout $10.00

[hraney]

Didn't notice in your signature, but does the truck have an auto tranny. I had a similar issue w/ an old gas burning car. I thought it was missing going down the highway. Turns out it was the torque converter kicking in and out of lock up.

[willfull04]

yeah, i've got the 4L80E. Did you just have to replace the torque converter and problem solved?

[deerefanatic]

yah, my grandma's truck does that alot at the 50-60 range. Only her's only does it when accelertating gently. Heavy acceleration and it goes away. I think it's torque converter stutter too. Probably should have the tranny flushed.......

[hraney]

I would start w/ a tranny flush and filter change. Probably needs it anyway. The problem I had was on an old TH400 and yes it had to have a TC. But... with all the electronics on (and our 6.5's are relatively simple) these things it could be a sensor/solenoid. Have you had an SES light or do you know if the truck has thrown any trouble codes?

[willfull04]

only SES code im getting is 44, EGR related and i disabled my EGR (max-e-torq eprom for non-egr engine, im just looking for a non-egr plenum to put on)