Work truck is a little sick....

[dmax06]

okay, it is brought to my attention that one of our work trucks around the farm is acting up in a couple of different ways....the truck is an '03. I don't drive the truck everyday, but lately i have gotten a few chances to ride and see what it's doin....
1) black smoke at startup, followed by a relatively high idle. After warming up, the truck will change idles every couple of seconds. With this change in idle, the temperature gauge, which normally stays pegged on the cool side will jump to the normal position for a little while, then fall back down. While driving, the truck will run fine for a minute, then start a fuel rattle for a couple of seconds, then back to normal. I found out that injectors were replaced about two years ago. im no mechanic, but im guessing another injector issue, but can't understand the temp gauge?
2) Sometimes when you slow down to turn or stop the tranny will downshift really hard in the last three gears, and almost seem like its gonna slide the tires on the last downshift.

lol, Sorry if this sounds a bit confusing, but im just curious what replies this will get. i've told the boss to let me take it somewhere to get it looked at, but we've just been too busy. thanks for any hints or clues of where to start or how long we can wait before a major issue? :thumb:

 

[bullfrogjohnson]

Sounds like the regulator is sticking. You need to log it.

 

[DAVe3283]

Since the engine idle changes as the temperature gauge moves, I'd guess a bad temperature probe or a bad connection to the probe.

The engine will set the idle speed based on coolant temperature (as well as timing). This would explain the varying idle and random timing knock, since the engine is changing the desired idle speed and timing, since it thinks the engine is getting very cold all of a sudden.

I'll bet a new temperature sensor (or fix loose wires?) will take care of those problems.

As far as the transmission, no idea, sorry.

 

[Cougar281]

Sounds like the regulator is sticking. You need to log it.

What he said.... The change in idle and fuel rattle sound like the rail pressure is not staying constant. The rattle is most likely high fuel pressure.

 

[68skylark455]

Check all the grounds on both sides of the block very close. A bad ground will cause you several headaches. The ecm needs them to operate everything correctly and with the smaller size wire gm started using in 99' we have had nothing but hell with broke wires and loose or broken grounds. I believe the 03 is the same as the 04 and there are 4 or 5 down by the oil pan towards the front of the motor on both sides of the block.

 

[dmax06]

ok, thanks guys. i'll look at it tomorrow if i have a chance. I don't really have a way to log it myself, since im running someone elses tunes, but i'll check the wires. thanks again!