2008 Silverado 4.3 Issues - Please Help

freefallin2000 · May 23, 2017

my wife and I recently purchased a 2008 Silverado base with the 4.3 and auto trans. Its a basic truck with crank windows. We bought it with 75k miles not knowing any of the owner history but it was clean and we got it for a nice deal, currently has 82k on it. There are several issues we need to fix before we sell to get a different truck.

1.) The AC fans are coming on right when you start the truck and a message will appear that reads "Engine Hot - AC Fans Turned Off". The temp gauge does move above 160 but the truck seems to drive just fine and coolant appears fine also. Is this a T-Stat issue? If not, what is the fix here?

2.) When you come to a full with your ft on the brake and then let off the brake to start driving again, it feels like the trans is downshifting into 1st at this time, as there is a fully noticeable clunk coming from directly where the trans is. Almost like the trans or converter is slipping or soothing and not engaging into gear until after you release the brake to start driving again. Could this be a driveshaft yoke gone bad? Trans issue? Programming issue?

3.) Intermittent no start issue where the truck just randomly will not start. The gauge lights sometimes flash randomly also. Took it to shop about a year ago and thought it was fixed, but it wasn't. Hasn't done it in a month or so (fingers crossed). The shop cut out the Viper aftermarket alarm that came with the truck and also installed a new ignition lock assembly (I think), got me a new key and also said they re-programmed it for the new key. After getting the truck back the second time, the front speakers and blinker sounds only work sporadically and not very often. I have to assume whatever they did cutting the alarm out is causing the sound issue. Any thoughts here? My buddy and I checked all of the engine ground wires and everything is grounded properly and getting proper voltage. I have read up on this and have found it can be anything from a bad ground cable, fuse, or ignition lock assembly. Help!

4.) When you floor it to pass someone on the hwy, it makes a very noticeable popping sound and hesitates almost like its bad plugs. The noise comes from right under the cab which makes me think it could be a clogged cat but I cant be certain. Anyone have any ideas on this also?

Sorry for the long thread and I will research tonight when I am home. Thanks in advance to anyone who can help us out. I cant afford to drop $1k at the Chevy dealer for them to just tell me " we think we fixed it" and have these issues come back to haunt me.

Sean

007matman · May 23, 2017

Sounds like some of that may be driveline slop. Did you check the ujoints for wear? There is also an issue I've seen with the slip joint on the driveshaft.

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007matman · May 23, 2017

Engine mounts too..

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freefallin2000 · May 23, 2017

Sounds like some of that may be driveline slop. Did you check the ujoints for wear? There is also an issue I've seen with the slip joint on the driveshaft.

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I sure haven't matman

007matman · May 23, 2017

Good luck

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freefallin2000 · May 23, 2017

Just ready thru this thread and it sounds like Tstat and/or pulling the fuse block/topping off the fluid levels in both the rad. and overflow could all help. Albeit, no has confirmed if this is the answer or not...

Anyone have any answers to any of the other issues I posted?

007matman · May 23, 2017

I would say t-stat but you're saying that the gages are normal and the truck seems to drive normal as well. Could it be a stuck code? Did you try connecting it to a computer and seeing if there are any codes in there?

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diyer2 · May 24, 2017

All this started recently? No problems before. Any work done to cause changes?

Go to auto store for a code check. It's free.

After its warmed up feel the rad hoses, top and bottom. They should be both be warm/hot.

Have you looked into rad after removing the rad cap. Do it when cold. Any crud.

1 AC fans? You mean cooling fans?

2 Try using trans in manual mode, not drive. This will help tell if it's trans related.

3 This will be a process of elimination to find it. Good Luck

4 Same thing, process of elimination.

All your problems have no clear cut answer IMO and if that's what you're looking for, sorry. The easiest place to start is with codes if any.

freefallin2000 · May 24, 2017

Thanks guys I will check it out.

MaverickZ71 · May 25, 2017

Have an auto parts store scan for diagnostic codes for free. Or if you subscribe to OnStar, press the blue button on the rearview mirror and tell them to run a remote diagnostic. Hopefully the scan can help diagnose your problems.

Normal operating temp on the gauge is 210 for these trucks. If you're not seeing anything above that, and if the sensor is ok and your coolant is good, full, and doesn't have any air pockets, then you're not really running hot. A lot of mornings my radiator fans will come on immediately at startup and run like mad for a minute or two, if my Auto AC is on--and the coolant isn't even warm yet; so I'd chalk that up to normal programming, except for your error message.

A "bump" from the driveshaft during acceleration and/or stop is normal for many of these trucks, unfortunately.

The warning chimes and blinker sounds on these trucks come from the driver's door front speaker. These speakers are infamous for cutting in and out, like there's a short in the wiring. Many people have tested the wiring and said there's no problem, and the only way to fix it is to replace speaker(s).

Unless the diagnostic indicates otherwise, your backfiring during acceleration may be solved by running a few tanks with some fuel system cleaner (Techron is what GM uses) and/or new spark plugs (AC Delco's are always compatible, some have had problems with other brands not running right). If you do the plugs, check the spark plug wires at the same time.