Hi there,

I know this is a Chevy board but after reading some threads I see that there are some GM certified people on here. I hope my question about my Yukon is welcome.

I have a 97 Yukon, 5.7L V8 4wd. It has recently cost us a ton of $$ as the head gasket went on it (coolant was leaking into the oil like mad). So I get it back from our trusted mechanic & I notice within a day that it is losing power constantly & the engine is pinging when you use the gas. I broughtit back ASAP as the mechanic says it's probably the timing. Long story short, I've been back now 3x & the timing is still off, it's firing too early. We've had this truck now 3 yrs& ithas awesome guts when you give gasbut since having the gaskets replaced it is a shadow of it's former self in that sense. The mechanic tells me the timing is hard to set on these trucks because there's apparently no set setting.

[sm=feedback.gif] So my question is.....how hard is it to set the timing on this thing?

After spending all that $$ with these guys, I'd hate to have to go somewhere else & pay to have it set properly, esp. since they've been good to us in the past,but I'm also gettingtired of having to go back.

Karen

Edited again b/c I can't spell today!

 

Your question is more than welcomed here. Since the yukon is basically a tahoe with a few minor differences.

First of all, the timing on the engine is not adjustable. But the tech did have to remove the distributor, and it sounds like it didn't go back together properly. If the distibutor isn't set right mechanically, then the computer can't adjust timing properly electronically.

 

Wow, thanks for your quick reply Shawn! Going by the invoice, they replaced the distributor cap & the distributor rotor as well so atleast we're dealing with new ones, I guess just not installed properly. I will give him a call on Tues. (Mon. being the holiday) set a time to bring it back in.

I'll let you know how it goes. Thanks Shawn!

Karen

 

Well, the call to my mechanic didn't go too well as he does not believe it's the distributor. He said the check engine light would've come on if it was(which it hasn't).
Could it be the catalytic converter as he mentioned?
Or could the timing chain have been stretched? That's another thing he mentioned.
This is very frustrating.

Crap - I still can't spell!

 

if it wasn't doing it before the work, why would it suddenly be something new like the converter? I think shawn is correct in that the distributor is not tweaked in right, even being slightly off may not be enough to set a code. I would try a different shop for an opinion...

 

I know, I've been thinking the exact same thing......aside from the coolant disappearing like mad before we had to have the head gaskets replaced, it was running with full power.

 

it is also possible that the plug wires are not in the right sequence, the truck will run and not set a code but the firing sequence is off. I would also check that all the wires are seated at both ends (cap and plugs)
Apinched or disconnected vacuum line can also cause lack of power and may not set codes.
Your mechanic may have done good work and just missed something simple, I suspect (but can't be completely ruled out)that is the problem rather then something new.
also check and make sure the check engine light is working, turn the key all the way to start but don't crank and verify that all the dash lights do come on, just a good sanity check...


EDIT
also what is the temp gauge reading after driving for a while? the gauge should rise as you drive and then start going back down after it peaks around 200. If I recall the thermostat is set to open at about 190 degrees