Thread: 125K Sierra timing chain?

just replace it with one of these International Class 7 Crew Cab Pickup - Truck Trend

What's the service manual say?

Performance chips work best when the engine is properly tuned in the first place.

Originally Posted by CBR929RE

just replace it with one of these International Class 7 Crew Cab Pickup - Truck Trend

My dad and I have drooled over the various versions of that thing for a couple years. Not practical, but I'd drive one.

First thing would be to check the timing and see whare it is before you go any further.

Timing chain should be fine unless you've driven that thing like a total hoon (which I doubt), and even then it wouldn't be the first thing I'd check. If mileage is off, start with the basics like spark plugs, plug wires, fuel filter, air filter, check for vacuum leaks, test the coil packs, check tires for proper inflation/wear, hook it up to a diagnostic machine.

Originally Posted by SerialThriller

Timing chain should be fine unless you've driven that thing like a total hoon (which I doubt), and even then it wouldn't be the first thing I'd check. If mileage is off, start with the basics like spark plugs, plug wires, fuel filter, air filter, check for vacuum leaks, test the coil packs, check tires for proper inflation/wear, hook it up to a diagnostic machine.

It is basically towing miles (50%+) so yes it has been flogged . New plugs, wires, tires are good (truck and trailer), air filter. Not sure on vacuum leaks as it doesn't have many hoses.... Also the coils might be a good idea though the plugs were nice color when I replaced them. How would the fuel filter affect mileage

Originally Posted by SheepOfBlue

So the mileage has dropped off on the Sierra a bit (about 2-3MPG non-towing).

Was it an apples to apples comparison?

In other words, does the fuel you are using now have a larger fraction of ethanol in it?

Originally Posted by Baketech

Was it an apples to apples comparison?

In other words, does the fuel you are using now have a larger fraction of ethanol in it?

We discussed that, it wasn't but a drop of 18 to 16 MPG with similar driving seems to high for just ethanol. Also the drop towing seems to be about 10% though it is hard to say because wind and a lead hoof can change that by a lot so there is a high variance.

I am surprised you of all people don't have something plugged into the OBDII port

www.scangauge.com is what I have, it was about 160$ (scangaugeII) on amazon and I got an extra cable with it. It will calculate your MPG for you based on sensor input and a few calibration factors, but more importantly it also lets you map a crapton of sensors right to the display. I realize it would be more helpful if it logged it, but I preferred realtime display because I want to see if it's just me putting my foot more into it on a given hill on a given day in different conditions, or if it's something else.

If you just want to log, I have used this stuff on corporate vehicles before with good success:
Vehicle tracking and monitoring solutions for small business, fleets, teens, and hobbyists by Davis

Although now that I have suggested a datalogger for your truck as the logical solution, your likely to blow the engine long before you complete the GPS clocked masterpiece , so I recommend whatever was said above

Originally Posted by SomeStrangeGuy

I am surprised you of all people don't have something plugged into the OBDII port

www.scangauge.com is what I have, it was about 160$ (scangaugeII) on amazon and I got an extra cable with it. It will calculate your MPG for you based on sensor input and a few calibration factors, but more importantly it also lets you map a crapton of sensors right to the display. I realize it would be more helpful if it logged it, but I preferred realtime display because I want to see if it's just me putting my foot more into it on a given hill on a given day in different conditions, or if it's something else.

If you just want to log, I have used this stuff on corporate vehicles before with good success:
Vehicle tracking and monitoring solutions for small business, fleets, teens, and hobbyists by Davis

Although now that I have suggested a datalogger for your truck as the logical solution, your likely to blow the engine long before you complete the GPS clocked masterpiece , so I recommend whatever was said above

OBDII Project Home

Just kidding. I am thinking worn not a bad sensor. Just trying to get all my winter projects and maintainance cued up since I am off next week. Though it might be a decent idea to plug my OBDII reader in.

O2 sensor could cause some issues, or a combination of a few things could be ganging up against you. Have you checked the simple crap like tire pressure, alignment, suspension wear? Maybe if the plant is ok, the issue is a parasitic resistance elsewhere in the system.

Have you had the fuel system cleaned/serviced? You can run something like GM's upper engine and fuel injector cleaner (PN 88861802) through it, or take it somewhere that can hook it up to equipment to properly clean the injectors, fuel rails, etc.

Originally Posted by SerialThriller

Have you had the fuel system cleaned/serviced? You can run something like GM's upper engine and fuel injector cleaner (PN 88861802) through it, or take it somewhere that can hook it up to equipment to properly clean the injectors, fuel rails, etc.

Hmmm no, I have run cleaner through periodically but it doesn't get the mileage it used to (only about 6K a year now) so it might getting varnishy...

Some good ideas folks, thanks well except CBR929RE

I forgot to mention, have you considered a Ridgeline?

Originally Posted by SomeStrangeGuy

I forgot to mention, have you considered a Ridgeline?

Paid for GMC that has as much or more tow capacity. I would go 3/4+ or motorhome from here.

Originally Posted by SheepOfBlue

Hmmm no, I have run cleaner through periodically but it doesn't get the mileage it used to (only about 6K a year now) so it might getting varnishy...

Some good ideas folks, thanks well except CBR929RE

hey my idea was great. you'd just have to upgrade your license to drive it but you'd be able to pull just about anything with it.

Originally Posted by Blorton

Actually, "that's not entirely accurate". They offer the option of a derated version limited to 25,999 pounds that qualifies for Class B operation. Or something like that. Lawl.

did not know they made a "little" one. and that weight is under a class B, you just need a regular class D which is a normal drivers license. 26001 and over you need a class B.