6.0 Engine Troubles

ssabens · September 15, 2009

Sorry about the generic title, but I have a few issues. Honestly, I feel that there is something wrong with my engine and/or transmission.

2007 Silverado, 6.0l, 52k miles,

Here goes:

1. Drove through a puddle, so water splashed up into the engine compartment, not sure what it hit but here is what happened:

a. While the air conditioner was running, the engine had little to no power, it was almost like it was starved for fuel - I would step on the gas pedal and nothing happened.

b. Turned of the A/C and the truck ran "normal"

c. Drove down the road a little more, turned on the A/C, same thing, little to no power when stepping on the gas - it got better the further I drove, I'm assuming that it's because the water was evaporating and no longer causing the issue.

- I checked for sparks at night, coming from the the plug wires, didn't see anything, the next thing I was going to do is spray the engine with some water and drive it, see what happens - but haven't had the time yet.

2. I recently had my starter replaced due to failure. There is still an intermittent problem where I'll get in and turn the key and nothing happens, no crank, no noise, no click - I'll just back the key off and then start the truck. There is no grinding or any odd sound with the starter, just the random times when I turn the key and nothing happens, almost seems like a ground problem.

3. I'm still having issues when I stop and sit at a red light where the truck basically surges forward, like the tranny is downshifting or something - of course it will never do it at the shop.

4. Getting the engine to downshift is sometimes impossible, just this morning I tried to get the truck to shift so I could accelerate faster, nothing, tried 1/2 throttle, tried 3/4, tried putting it to the floor, nothing, it just would not downshift.

5. Sometimes (when I do get the engine to down shift properly), there is quite a loud clunk, definetly not a smooth shift. I have done a full 50k mile service, which included a transmission flush (but that didn't help).

6. Towing. 5000 pounds (includes trailer weight). This shouldn't be much of an issue for this truck, but it seems to be. The truck works pretty hard going up-hill on the highway (not even steep grades) I have the 3.73 ratio. Tranny temp rises to 192 (not sure how hot it should get, but wanted to give as much detail as possible). I don't go over 65 when towing, usually around 55-60mph

The main problem with all of these issues is that they are intermittent, or require certain conditions to get the issue to happen. Any suggestions are appreciated.

Stevens03 · September 15, 2009

I'll offer my 2 cents worth of advice. Starting issue could be a bad ignition switch. The surge could be caused from dirty MAF sensor, and also cause the erratic shifting issue. Between 35-45, it won't down shift into first.. not sure if thats your issue or not, but a custom tune could help that by raising the rev-limiter. The clunk could be coming from bad or going bad u-joints, and just because GM by nature has a loud drive line, you can repack your slip yoke with grease to help take up some of the slack and noise. I'd check the u-joints, and definitely repack the slip yoke. Also, checking for spark at night is a good thing, but most often you won't see it because it won't do it under normal idle. Usually from my experience, you won't feel it or hear it till your under load

What kind of trailer do you tow? Have you checked the tire pressure on the trailer tires. I always try to pump them up with in 5psi of max pressure for ALOT better rolling resistance. Also, if the trailer has a flat front, the wind resistance can greatly effect the towing effort. Are you using the tow/haul feature and are you towing in drive or 3rd? 192 tranny temp isn't bad... If it goes above 210, then I'd start looking for problems. Maybe some one here will post it, but I believe there was a TSB out about something dealing with no-power while towing under load. But I don't remember the details.

Not sure if much of that helps, but maybe it's a start

ssabens · September 15, 2009

Definitely a start, thanks Steve.

So I'll have the wife step on the gas to look for spark. And possibly look into everything else you listed. I'm hesitant to get the custom tune because of warranty issues (I have an extended warranty); although I've heard that it pretty much makes everything better.

As far as the trailer, it's a boat, so no flat front, I do need to check the tire pressure though. I use the tow/haul mode when pulling that, not 3rd gear. I'll have to check on the TSB.

I think another problem is that I came from a 2002 Tundra that ran so smooth, I'm starting to regret it, but wanted the extra cab room (crew) for my son in the back and more tow power because I knew I was getting a larger boat.

Thanks!

Stevens03 · September 15, 2009

Oh good lord, the Vmax should be a better motor than the 02 tundra had. Your truck should be able to handle close to 10,200 I believe having the 3.73 gears. 5000 lbs boat shouldn't be an issue, so maybe the TSB issue is your problem. If you have the extended warranty, I'd take it in.

The MAF sensor can be guilty for alot of different issues. I don't think people give it the respect it deserves

I understand what your saying about the custom tune, but this topic has been discussed to death but one of the reasons I use diablo

Edit:

I can't find it, but there was a post a while back about a TSB concerning the Vmax 6.0 and poor engine performance while towing. Maybe someone else can post that up or at least give you a number to check with the dealership for.

Good luck.

ssabens · October 3, 2009

Well, I didn't see any light coming from the wires (idle or under load), but did narrow the wet engine issue down to the passenger side. I bought some new wires anyway, just to see if that solves it. I figure that at 50k miles, it could use new wires anyway (I went with the Napa Belden wires); they'll go in tomorrow.

I do wish I could get that custom tune, but I just have a feeling that I'll need to be replacing a transmission in the near future. I was looking at the Diablo Predator, people are pretty upset about the whole "No TCM support" thing. Now I see that they might be working on it...that would be nice.